Publications by authors named "Alexander J Szalai"

66 Publications

Decreased Levels of STAT1 and Interferon-γ-Induced STAT1 Phosphorylation in Rheumatoid Arthritis CD4 and CD8 T Cells.

ACR Open Rheumatol 2021 Mar 28. Epub 2021 Mar 28.

The University of Alabama at Birmingham.

Objective: We investigated whether a previously reported association of IFNGR expression with rheumatoid arthritis (RA) and its radiographic severity reflects differences in proximal interferon-γ (IFN-γ) signaling in T cells from patients with RA compared with healthy controls (HC).

Methods: Using phosphoflow cytometry, we compared IFN-γ-stimulated signal transducer and activator of transcription 1 (STAT1) activation in CD4 and CD8 T-cell populations from patients with RA and HC.

Results: Compared with controls, patients with RA had a higher proportion of CD4 T cells, associated with expansion of the CD4 effector memory subset. Several CD4 T-cell types exhibited reduced IFN-γ-induced phosphoSTAT1 (pSTAT1 ) in patients with RA compared with HC. Engaging the T-cell receptor (TCR) complex on CD4 T cells during IFN-γ stimulation abrogated the reduction in STAT1 activation in patients with RA but had no effect in HC. The phosphorylation of STAT1 was similar in CD4 T cells from patients with RA and HC. In contrast to CD4 T cells, IFN-γ-induced pSTAT1 levels in CD8 T cells were equivalent or higher in patients with RA compared with HC. Total STAT1 levels (phosphorylated + unphosphorylated) were lower in CD4 and CD8 T cells from patients with RA compared with HC.

Conclusion: We report diminished IFN-γ-induced pSTAT1 levels in CD4 T cells in patients with RA, which were restored by TCR engagement. There were lower levels of total STAT1 in patients with RA compared with HC, but this likely does not explain diminished IFN-γ-induced pSTAT1 levels in CD4 T cells because activation in CD8 T cells was higher or equivalent to that seen in HC. The enhanced IFNGR expression in patients with RA reported previously may reflect a compensatory mechanism to overcome deficiency in IFN-γ responsiveness.
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http://dx.doi.org/10.1002/acr2.11244DOI Listing
March 2021

Therapeutic Lowering of C-Reactive Protein.

Front Immunol 2020 29;11:619564. Epub 2021 Jan 29.

Division of Clinical Immunology & Rheumatology, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, United States.

In the blood of healthy individuals C-reactive protein (CRP) is typically quite scarce, whereas its blood concentration can rise robustly and rapidly in response to tissue damage and inflammation associated with trauma and infectious and non-infectious diseases. Consequently, CRP plasma or serum levels are routinely monitored in inpatients to gauge the severity of their initial illness and injury and their subsequent response to therapy and return to health. Its clinical utility as a faithful barometer of inflammation notwithstanding, it is often wrongly concluded that the biological actions of CRP (whatever they may be) are manifested only when blood CRP is elevated. In fact over the last decades, studies done in humans and animals (e.g. human CRP transgenic and CRP knockout mice) have shown that CRP is an important mediator of biological activities even in the absence of significant blood elevation, i.e. even at baseline levels. In this review we briefly recap the history of CRP, including a description of its discovery, early clinical use, and biosynthesis at baseline and during the acute phase response. Next we overview evidence that we and others have generated using animal models of arthritis, neointimal hyperplasia, and acute kidney injury that baseline CRP exerts important biological effects. In closing we discuss the possibility that therapeutic lowering of baseline CRP might be a useful way to treat certain diseases, including cancer.
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http://dx.doi.org/10.3389/fimmu.2020.619564DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7901964PMC
January 2021

Mice expressing the variant rs1143679 allele of ITGAM (CD11b) show impaired DC-mediated T cell proliferation.

Mamm Genome 2019 10 31;30(9-10):245-259. Epub 2019 Oct 31.

Department of Genetics, University of Alabama at Birmingham, 1700 University Blvd., Birmingham, AL, 35294-0013, USA.

Genome-wide association studies (GWAS) and functional genomic analyses have implicated several ITGAM (CD11b) single-nucleotide polymorphisms (SNPs) in the development of SLE and other disorders. ITGAM encodes the α chain of the β integrin Mac-1, a receptor that plays important roles in myeloid cell functions. The ITGAM SNP rs1143679, which results in an arginine to histidine change at amino acid position 77 of the CD11b protein, has been shown to reduce binding to several ligands and to alter Mac-1-mediated cellular response in vitro. Importantly, however, the potential contribution of this SNP variant to the initiation and/or progression of immune and inflammatory processes in vivo remains unexplored. Herein, we describe for the first time the generation and characterization of a mouse line expressing the 77His variant of CD11b. Surprisingly, we found that 77His did not significantly affect Mac-1-mediated leukocyte migration and activation as assessed using thioglycollate-induced peritonitis and LPS/TNF-α-induced dermal inflammation models. In contrast, expression of this variant did alter T cell immunity, as evidenced by significantly reduced proliferation of ovalbumin (OVA)-specific transgenic T cells in 77His mice immunized with OVA. Reduced antigen-specific T cell proliferation was also observed when either 77His splenic dendritic cells (DCs) or bone marrow-derived DCs were used as antigen-presenting cells (APCs). Although more work is necessary to determine how this alteration might influence the development of SLE or other diseases, these in vivo findings suggest that the 77His variant of CD11b can compromise the ability of DCs to induce antigen-driven T cell proliferation.
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http://dx.doi.org/10.1007/s00335-019-09819-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6842653PMC
October 2019

C-Reactive Protein Promotes the Expansion of Myeloid Derived Cells With Suppressor Functions.

Front Immunol 2019 18;10:2183. Epub 2019 Sep 18.

Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States.

Previously we established that human C-reactive protein (CRP) exacerbates mouse acute kidney injury and that the effect was associated with heightened renal accumulation of myeloid derived cells with suppressor functions (MDSC). Herein we provide direct evidence that CRP modulates the development and suppressive actions of MDSCs . We demonstrate that CRP dose-dependently increases the generation of MDSC from wild type mouse bone marrow progenitors and enhances MDSC production of intracellular reactive oxygen species (iROS). When added to co-cultures, CRP significantly enhanced the ability of MDSCs to suppress CD3/CD28-stimulated T cell proliferation. Experiments using MDSCs from FcγRIIB deficient mice (FcγRIIB) showed that CRP's ability to expand MDSCs and trigger their increased production of iROS was FcγRIIB-independent, whereas its ability to enhance the MDSC T cell suppressive action was FcγRIIB-dependent. Importantly, CRP also enabled freshly isolated primary human neutrophils to suppress proliferation of autologous T cells. These findings suggest that CRP might be an endogenous regulator of MDSC numbers and actions .
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http://dx.doi.org/10.3389/fimmu.2019.02183DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6759522PMC
November 2020

C-Reactive Protein Impairs Dendritic Cell Development, Maturation, and Function: Implications for Peripheral Tolerance.

Front Immunol 2018 5;9:372. Epub 2018 Mar 5.

Department of Medicine, Division of Clinical Immunology & Rheumatology, University of Alabama at Birmingham, Birmingham, AL, United States.

C-reactive protein (CRP) is the prototypical acute phase reactant, increasing in blood concentration rapidly and several-fold in response to inflammation. Recent evidence indicates that CRP has an important physiological role even at low, baseline levels, or in the absence of overt inflammation. For example, we have shown that human CRP inhibits the progression of experimental autoimmune encephalomyelitis (EAE) in CRP transgenic mice by shifting CD4 T cells away from the T1 and toward the T2 subset. Notably, this action required the inhibitory Fcγ receptor IIB (FcγRIIB), but did not require high levels of human CRP. Herein, we sought to determine if CRP's influence in EAE might be explained by CRP acting on dendritic cells (DC; antigen presenting cells known to express FcγRIIB). We found that CRP (50 µg/ml) reduced the yield of CD11c bone marrow-derived DCs (BMDCs) and CRP (≥5 μg/ml) prevented their full expression of major histocompatibility complex class II and the co-stimulatory molecules CD86 and CD40. CRP also decreased the ability of BMDCs to stimulate antigen-driven proliferation of T cells . Importantly, if the BMDCs were genetically deficient in mouse FcγRIIB then (i) the ability of CRP to alter BMDC surface phenotype and impair T cell proliferation was ablated and (ii) CD11c-driven expression of a human transgene rescued the CRP effect. Lastly, the protective influence of CRP in EAE was fully restored in mice with CD11c-driven human FcγRIIB expression. These findings add to the growing evidence that CRP has important biological effects even in the absence of an acute phase response, i.e., CRP acts as a tonic suppressor of the adaptive immune system. The ability of CRP to suppress development, maturation, and function of DCs implicates CRP in the maintenance of peripheral T cell tolerance.
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http://dx.doi.org/10.3389/fimmu.2018.00372DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5845098PMC
April 2019

Hyposialylated IgG activates endothelial IgG receptor FcγRIIB to promote obesity-induced insulin resistance.

J Clin Invest 2018 01 27;128(1):309-322. Epub 2017 Nov 27.

Center for Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.

Type 2 diabetes mellitus (T2DM) is a common complication of obesity. Here, we have shown that activation of the IgG receptor FcγRIIB in endothelium by hyposialylated IgG plays an important role in obesity-induced insulin resistance. Despite becoming obese on a high-fat diet (HFD), mice lacking FcγRIIB globally or selectively in endothelium were protected from insulin resistance as a result of the preservation of insulin delivery to skeletal muscle and resulting maintenance of muscle glucose disposal. IgG transfer in IgG-deficient mice implicated IgG as the pathogenetic ligand for endothelial FcγRIIB in obesity-induced insulin resistance. Moreover, IgG transferred from patients with T2DM but not from metabolically healthy subjects caused insulin resistance in IgG-deficient mice via FcγRIIB, indicating that similar processes may be operative in T2DM in humans. Mechanistically, the activation of FcγRIIB by IgG from obese mice impaired endothelial cell insulin transcytosis in culture and in vivo. These effects were attributed to hyposialylation of the Fc glycan, and IgG from T2DM patients was also hyposialylated. In HFD-fed mice, supplementation with the sialic acid precursor N-acetyl-D-mannosamine restored IgG sialylation and preserved insulin sensitivity without affecting weight gain. Thus, IgG sialylation and endothelial FcγRIIB may represent promising therapeutic targets to sever the link between obesity and T2DM.
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http://dx.doi.org/10.1172/JCI89333DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5749535PMC
January 2018

C-reactive protein promotes acute kidney injury via Smad3-dependent inhibition of CDK2/cyclin E.

Kidney Int 2016 09 26;90(3):610-26. Epub 2016 Jul 26.

Department of Medicine and Therapeutics, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China. Electronic address:

Acute kidney injury (AKI) is exacerbated in C-reactive protein transgenic mice but alleviated in Smad3 knockout mice. Here we used C-reactive protein transgenic/Smad3 wild-type and C-reactive protein transgenic/Smad3 knockout mice to investigate the signaling mechanisms by which C-reactive protein promotes AKI. Serum creatinine was elevated, and the extent of tubular epithelial cell necrosis following ischemia/reperfusion-induced AKI was greater in C-reactive protein transgenics but was blunted when Smad3 was deleted. Exacerbation of AKI in C-reactive protein transgenics was associated with increased TGF-β/Smad3 signaling and expression of the cyclin kinase inhibitor p27, but decreased phosphorylated CDK2 and expression of cyclin E. Concomitantly, tubular epithelial cell proliferation was arrested at the G1 phase in C-reactive protein transgenics with fewer cells entering the S-phase cell cycle as evidenced by fewer bromodeoxyuridine-positive cells. In contrast, the protection from AKI in C-reactive protein transgenic/Smad3 knockout mice was associated with decreased expression of p27 and promotion of CDK2/cyclin E-dependent G1/S transition of tubular epithelial cells. In vitro studies using tubular epithelial cells showed that C-reactive protein activates Smad3 via both TGF-β-dependent and ERK/MAPK cross talk mechanisms, Smad3 bound directly to p27, and blockade of Smad3 or the Fc receptor CD32 prevented C-reactive protein-induced p27-dependent G1 cell cycle arrest. In vivo, treatment of C-reactive protein transgenics with a Smad3 inhibitor largely improved AKI outcomes. Thus, C-reactive protein may promote AKI by impairing tubular epithelial cell regeneration via the CD32-Smad3-p27-driven inhibition of the CDK2/cyclin E complex. Targeting Smad3 may offer a new treatment approach for AKI.
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http://dx.doi.org/10.1016/j.kint.2016.06.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5672807PMC
September 2016

C-reactive protein exacerbates renal ischemia-reperfusion injury: are myeloid-derived suppressor cells to blame?

Am J Physiol Renal Physiol 2016 07 6;311(1):F176-81. Epub 2016 Apr 6.

Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and

Myeloid-derived suppressor cells (MDSCs) are a CD11b(+)Gr1(+) population in mice that can be separated into granulocytic (g-MDSC) and monocytic (m-MDSC) subtypes based on their expression of Ly6G and Ly6C. Both MDSC subtypes are potent suppressors of T cell immunity, and their contribution has been investigated in a plethora of diseases including renal cancer, renal transplant, and chronic kidney disease. Whether MDSCs contribute to the pathogenesis of acute kidney injury (AKI) remains unknown. Herein, using human C-reactive protein (CRP) transgenic (CRPtg) and CRP-deficient mice (CRP(-/-)) subjected to bilateral renal ischemia-reperfusion injury (IRI), we confirm our earlier finding that CRP exacerbates renal IRI and show for the first time that this effect is accompanied in CRPtg mice by a shift in the balance of kidney-infiltrating MDSCs toward a suppressive Ly6G(+)Ly6C(low) g-MDSC subtype. In CRPtg mice, direct depletion of g-MDSCs (using an anti-Gr1 monoclonal antibody) reduced the albuminuria caused by renal IRI, confirming they play a deleterious role. Remarkably, treatment of CRPtg mice with an antisense oligonucleotide that specifically blocks the human CRP acute-phase response also led to a reduction in renal g-MDSC numbers and improved albuminuria after renal IRI. Our study in CRPtg mice provides new evidence that MDSCs participate in the pathogenesis of renal IRI and shows that their pharmacological depletion is beneficial. If ongoing investigations confirm that CRP is an endogenous regulator of MDSCs in CRPtg mice, and if this action is recapitulated in humans, then targeting CRP or/and MDSCs might offer a new approach for the treatment of AKI.
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http://dx.doi.org/10.1152/ajprenal.00107.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4967164PMC
July 2016

Human C-reactive protein impedes entry of leptin into the CNS and attenuates its physiological actions in the CNS.

Biochem J 2016 05 1;473(9):1215-24. Epub 2016 Mar 1.

Collaborative Innovation Center for Cancer Medicine, School of Biological Sciences and Bioengineering, South China University of Technology, Guangzhou, Guangdong, 510640, China

Defective central leptin signalling and impaired leptin entry into the CNS (central nervous system) represent two important aspects of leptin resistance in obesity. In the present study, we tested whether circulating human CRP (C-reactive protein) not only diminishes signalling of leptin within the CNS, but also impedes this adipokine's access to the CNS. Peripheral infusion of human CRP together with co-infused human leptin was associated with significantly decreased leptin content in the CSF of ob/ob mice. Furthermore, following peripheral infusion of human leptin, the CSF (cerebrospinal fluid) concentration of leptin in transgenic mice overexpressing human CRP was sharply lower than that achieved in similarly infused wild-type mice. Administration of LPS (lipopolysaccharide) to human CRP-transgenic mice dramatically elevated the concentrations of human CRP in the CSF. The i.c.v. (intracerebroventricular) delivery of human CRP into the lateral ventricles of ob/ob mice blocked the satiety and weight-reducing actions of human leptin, but not those of mouse leptin. I.c.v. injection of human CRP abolished hypothalamic signalling by human leptin, and ameliorated the effects of leptin on the expression of NPY (neuropeptide Y), AgRP (Agouti-related protein), POMC (pro-opiomelanocortin) and SOCS-3 (suppressor of cytokine signalling 3). Human CRP can impede the access of leptin to the CNS, and elevation of human CRP within the CNS can have a negative impact on the physiological actions of leptin.
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http://dx.doi.org/10.1042/BJ20151282DOI Listing
May 2016

Hepatic but Not CNS-Expressed Human C-Reactive Protein Inhibits Experimental Autoimmune Encephalomyelitis in Transgenic Mice.

Autoimmune Dis 2015 3;2015:640171. Epub 2015 Sep 3.

Department of Medicine, The University of Alabama Birmingham, Birmingham, AL 35294, USA.

We recently demonstrated that human C-reactive protein (CRP), expressed hepatically in transgenic mice (CRPtg), improved the outcome of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS). The liver is the primary site of CRP synthesis in humans and in CRPtg mice but is also expressed by both at low levels in the CNS. To determine if CNS expression of human CRP is sufficient to impact EAE, we generated neuronal CRP transgenic mice (nCRPtg) wherein human CRP expression is driven by the neuron-specific Ca(2+)/calmodulin-dependent protein kinase IIα (CaMKIIα) gene promoter. We found that hepatically expressed/blood-borne CRP, but not CNS expressed CRP, lessened EAE severity. These outcomes indicate that the protective actions of human CRP in EAE are manifested in the periphery and not in the CNS and reveal a previously unappreciated site specificity for the beneficial actions of CRP in CNS disease.
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http://dx.doi.org/10.1155/2015/640171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4573232PMC
September 2015

Effects of the Dietary ω3:ω6 Fatty Acid Ratio on Body Fat and Inflammation in Zebrafish (Danio rerio).

Comp Med 2015 Aug;65(4):289-94

Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, USA.

The diets of populations in industrialized nations have shifted to dramatically increased consumption of ω6 polyunsaturated fatty acids (PUFA), with a corresponding decrease in the consumption of ω3 PUFA. This dietary shift may be related to observed increases in obesity, chronic inflammation, and comorbidities in the human population. We examined the effects of ω3:ω6 fatty acid ratios in the context of constant total dietary lipid on the growth, total body fat, and responses of key inflammatory markers in adult zebrafish (Danio rerio). Zebrafish were fed diets in which the ω3:ω6 PUFA ratios were representative of those in a purported ancestral diet (1:2) and more contemporary Western diets (1:5 and 1:8). After 5 mo, weight gain (fat free mass) of zebrafish was highest for those that received the 1:8 ratio treatment, but total body fat was lowest at this ratio. Measured by quantitative real-time RT-PCR, mRNA levels from liver samples of 3 chronic inflammatory response genes (C-reactive protein, serum amyloid A, and vitellogenin) were lowest at the 1:8 ratio. These data provide evidence of the ability to alter zebrafish growth and body composition through the quality of dietary lipid and support the application of this model to investigations of human health and disease related to fat metabolism.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4549674PMC
August 2015

C-reactive protein directly suppresses Th1 cell differentiation and alleviates experimental autoimmune encephalomyelitis.

J Immunol 2015 Jun 27;194(11):5243-52. Epub 2015 Apr 27.

Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, People's Republic of China; Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Lanzhou University, Lanzhou 730000, People's Republic of China

Human C-reactive protein (CRP) is a serum-soluble pattern recognition receptor that serves as a marker of inflammation and directly contributes to innate immunity. In this study, we show that human CRP also directly contributes to adaptive immunity, that is, native CRP binds specifically to human Jurkat T cells and to mouse naive CD4(+) T cells and modulates their Th1 and Th2 responses. In vitro both exogenously added (purified) and endogenously expressed (via transfection) human CRP inhibited Th1 differentiation and augmented Th2 differentiation of naive CD4(+) T cells. In vivo for human CRP transgenic compared with wild-type mice, a lesser proportion of the T cells recovered from the spleens of healthy animals were Th1 cells. Moreover, in both CRP transgenic mice and in wild-type mice treated with human CRP, during myelin oligodendrocyte glycoprotein peptide-induced experimental autoimmune encephalomyelitis both the Th1 cell response and disease severity were inhibited. These pattern recognition-independent actions of CRP directly on T cells highlights the potential for this soluble pattern recognition receptor to act as a tonic regulator of immunity, shaping global adaptive immune responses during both homeostasis and disease.
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http://dx.doi.org/10.4049/jimmunol.1402909DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4433796PMC
June 2015

Human neutrophil flow chamber adhesion assay.

J Vis Exp 2014 Jul 2(89). Epub 2014 Jul 2.

Department of Medicine, University of Alabama at Birmingham;

Neutrophil firm adhesion to endothelial cells plays a critical role in inflammation in both health and disease. The process of neutrophil firm adhesion involves many different adhesion molecules including members of the β2 integrin family and their counter-receptors of the ICAM family. Recently, naturally occurring genetic variants in both β2 integrins and ICAMs are reported to be associated with autoimmune disease. Thus, the quantitative adhesive capacity of neutrophils from individuals with varying allelic forms of these adhesion molecules is important to study in relation to mechanisms underlying development of autoimmunity. Adhesion studies in flow chamber systems can create an environment with fluid shear stress similar to that observed in the blood vessel environment in vivo. Here, we present a method using a flow chamber assay system to study the quantitative adhesive properties of human peripheral blood neutrophils to human umbilical vein endothelial cell (HUVEC) and to purified ligand substrates. With this method, the neutrophil adhesive capacities from donors with different allelic variants in adhesion receptors can be assessed and compared. This method can also be modified to assess adhesion of other primary cell types or cell lines.
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http://dx.doi.org/10.3791/51410DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4166108PMC
July 2014

Deletion of C-reactive protein ameliorates experimental cerebral malaria?

Trans R Soc Trop Med Hyg 2014 Sep 7;108(9):591-3. Epub 2014 Jul 7.

Department of Microbiology, The University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.

Background: C-reactive protein (CRP) level correlates with parasitemia and severity of malaria, but whether this reflects causality remains unknown.

Methods: Using CRP-transgenic and CRP-deficient mice we compared the onset and severity of experimental cerebral malaria (ECM) induced by Plasmodium berghei ANKA (PbA).

Results: CRP-deficient mice were most resistant to ECM.

Conclusions: CRP might contribute to the development of cerebral malaria, rather than protect against it.
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http://dx.doi.org/10.1093/trstmh/tru098DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4192040PMC
September 2014

Estrogen effects on vascular inflammation are age dependent: role of estrogen receptors.

Arterioscler Thromb Vasc Biol 2014 Jul 29;34(7):1477-1485. Epub 2014 May 29.

Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology and Infertility (M.R.B.), Vascular Biology and Hypertension Program, Division of Cardiovascular Disease (D.X., Y-F.C., S.O., F.G.H.) and the Division of Clinical Immunology and Rheumatology (A.J.S.), Department of Medicine, and the School of Medicine (A.K.), The University of Alabama at Birmingham, Birmingham, AL 35294, USA, Section of Cardiology, Birmingham Veteran's Administration Medical Center, Birmingham, AL 35294, USA (F.G.H.).

Objective: 17β-Estradiol (E2) offers cardiovascular protection in young female animals and postmenopausal women. In contrast, randomized trials of menopausal hormones performed in older women have shown harm or no cardiovascular benefit. We hypothesize that E2 effects on vascular inflammation are age dependent.

Approach And Results: Young (10 weeks) and aged (52 weeks) female C57BL/6 mice were used as source for primary cultures of bone marrow-derived macrophages (BMMs) and vascular smooth muscle cells (VSMCs). E2 pretreatment of cells derived from young mice attenuated C-reactive protein (CRP)-induced expression of inflammatory mediators. In contrast, E2 pretreatment of cells from aged mice did not alter (BMMs) or paradoxically exaggerated (VSMCs) inflammatory mediator response to CRP. Using E2 receptor (ER) knockout mice, we demonstrated that E2 regulates inflammatory response to CRP in BMMs via ERα and in VSMCs via ERβ. BMMs derived from aged (versus young) mice expressed significantly less ERα mRNA and protein. A selective ligand of the novel ER GPR30 reproduced the E2 effects in BMMs and VSMCs. Unlike in young mice, E2 did not reduce neointima formation in ligated carotid arteries of aged CRP transgenic mice.

Conclusions: E2 attenuates inflammatory response to CRP in BMMs and VSMCs derived from young but not aged mice and reduces neointima formation in injured carotid arteries of young but not aged CRP transgenic mice. ERα expression in BMMs is greatly diminished with aging. These data suggest that vasoprotective effects of E2 are age dependent and may explain the vasotoxic effects of E2 seen in clinical trials of postmenopausal women.
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http://dx.doi.org/10.1161/ATVBAHA.114.303629DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4227403PMC
July 2014

Associations between abnormal rod-mediated dark adaptation and health and functioning in older adults with normal macular health.

Invest Ophthalmol Vis Sci 2014 May 22;55(8):4776-89. Epub 2014 May 22.

Department of Ophthalmology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States Department of Epidemiology, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama, United States.

Purpose: Delayed rod-mediated dark adaptation (DA) is characteristic of early age-related macular degeneration (AMD) and also can be observed in some older adults in normal macular health. We examine cross-sectional associations between rod-mediated DA and risk factors for AMD in older adults in normal macular health.

Methods: The sample consisted of adults aged ≥60 years old in normal macular health per grading of fundus photos using an established disease classification system. Rod-mediated DA was measured psychophysically following a photobleach using a computer-automated dark adaptometer with targets centered at 5° on the inferior vertical meridian. The speed of DA was characterized by the rod-intercept value, with abnormal DA defined as rod-intercept ≥ 12.3 minutes. We assessed several health and functional characteristics that the literature has suggested increase AMD risk (e.g., smoking, alcohol use, inflammatory markers, apolipoproteins, low luminance visual acuity, chronic medical conditions, body mass, family history).

Results: Among 381 participants (mean age, 68.5 years; SD, 5.5), 78% had normal and 22% had abnormal DA, with the prevalence of abnormal DA increasing with age. After age-adjustment, abnormal DA was associated with increased odds of elevated C-reactive protein (CRP), heavy use of or abstention from alcohol, high blood pressure, and drop in visual acuity under mesopic conditions.

Conclusions: Despite having normal macular health according to accepted definitions of AMD presence, approximately one-quarter of older adults recruited from primary eye care clinics had abnormal DA, which was associated with known risk factors for AMD, including elevated CRP.
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http://dx.doi.org/10.1167/iovs.14-14502DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4122017PMC
May 2014

Inhibiting C-reactive protein for the treatment of cardiovascular disease: promising evidence from rodent models.

Mediators Inflamm 2014 2;2014:353614. Epub 2014 Apr 2.

Isis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92008, USA.

Raised blood C-reactive protein (CRP) level is a predictor of cardiovascular events, but whether blood CRP is causal in the disease process is unknown. The latter would best be defined by pharmacological inhibition of the protein in the context of a randomized case-control study. However, no CRP specific drug is currently available so such a prospective study cannot be performed. Blood CRP is synthesized primarily in the liver and the liver is an organ where antisense oligonucleotide (ASO) drugs accumulate. Taking advantage of this we evaluated the efficacy of CRP specific ASOs in rodents with experimentally induced cardiovascular damage. Treating rats for 4 weeks with a rat CRP-specific ASO achieved >60% reduction of blood CRP. Notably, this effect was associated with improved heart function and pathology following myocardial infarction (induced by ligation of the left anterior descending artery). Likewise in human CRP transgenic mice treated for 2 weeks with a human CRP-specific ASO, blood human CRP was reduced by >70% and carotid artery patency was improved (2 weeks after surgical ligation). CRP specific ASOs might pave the way towards a placebo-controlled trial that could clarify the role of CRP in cardiovascular disease.
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http://dx.doi.org/10.1155/2014/353614DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3996300PMC
December 2014

C-reactive protein promotes acute kidney injury by impairing G1/S-dependent tubular epithelium cell regeneration.

Clin Sci (Lond) 2014 May;126(9):645-59

*Department of Nephrology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.

CRP (C-reactive protein) is regarded as an inflammatory biomarker in AKI (acute kidney injury), but its exact role in AKI remains unclear. Thus we sought to investigate the role of CRP in AKI. Clinically, elevated serum CRP levels were found to associate closely with increased serum creatinine and urea levels (P<0.01) in patients with AKI, which then fell after recovery from AKI. To determine the role of CRP in AKI, an ischaemia/reperfusion mouse model of AKI was developed using Tg (transgenic) mice that express human CRP. Compared with the WT (wild-type) mice, CRP Tg mice developed more severe renal injury at 24 h after ischaemia as determined by significantly increased serum creatinine and tubular necrosis. This was associated with an impaired TEC (tubular epithelium cell) regeneration as shown by an over 60% reduction in PCNA+ (proliferating-cell nuclear antigen) and BrdU+ (bromodeoxyuridine) TECs in CRP Tg mice with AKI. In vitro, the addition of CRP to a human TEC line (HK-2) also largely suppressed the proliferation of TECs. The functional role of CRP in AKI was demonstrated further by the blocking of CRP binding to the FcγRII (Fcγ receptor II) with a neutralizing anti-CD32 antibody, which restored TEC proliferation and prevented AKI in CRP Tg mice. Moreover, we found that impaired G1/S transition by suppression of the phosphorylation of CDK2 (cyclin-dependent kinase 2) and expression of cyclin E may be a key mechanism by which CRP inhibits TEC regeneration during the AKI repair process. In conclusion, CRP plays a pathogenic role in AKI by inhibiting G1/S-dependent TEC regeneration. The results of the present study suggest that targeting CRP signalling may offer a new therapeutic potential for AKI.
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http://dx.doi.org/10.1042/CS20130471DOI Listing
May 2014

Multiple lupus-associated ITGAM variants alter Mac-1 functions on neutrophils.

Arthritis Rheum 2013 Nov;65(11):2907-16

University of Alabama at, Birmingham.

Objective: Multiple studies have demonstrated that single-nucleotide polymorphisms (SNPs) in the ITGAM locus (including the nonsynonymous SNPs rs1143679, rs1143678, and rs1143683) are associated with systemic lupus erythematosus (SLE). ITGAM encodes the protein CD11b, a subunit of the β2 integrin Mac-1. The purpose of this study was to determine the effects of ITGAM genetic variation on the biologic functions of neutrophil Mac-1.

Methods: Neutrophils from ITGAM-genotyped and -sequenced healthy donors were isolated for functional studies. The phagocytic capacity of neutrophil ITGAM variants was probed with complement-coated erythrocytes, serum-treated zymosan, heat-treated zymosan, and IgG-coated erythrocytes. The adhesion capacity of ITGAM variants, in adhering to either purified intercellular adhesion molecule 1 or tumor necrosis factor α-stimulated endothelial cells, was assessed in a flow chamber. Expression levels of total CD11b and activation of CD11b were assessed by flow cytometry.

Results: Mac-1-mediated neutrophil phagocytosis, determined in cultures with 2 different complement-coated particles, was significantly reduced in individuals with nonsynonymous variant alleles of ITGAM. This reduction in phagocytosis was related to variation at either rs1143679 (in the β-propeller region) or rs1143678/rs1143683 (highly linked SNPs in the cytoplasmic/calf-1 regions). Phagocytosis mediated by Fcγ receptors was also significantly reduced in donors with variant ITGAM alleles. Similarly, firm adhesion of neutrophils was significantly reduced in individuals with variant ITGAM alleles. These functional alterations were not attributable to differences in total receptor expression or activation.

Conclusion: The nonsynonymous ITGAM variants rs1143679 and rs1143678/rs113683 contribute to altered Mac-1 function on neutrophils. These results underscore the need to consider multiple nonsynonymous SNPs when assessing the functional consequences of ITGAM variation on immune cell processes and the risk of SLE.
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http://dx.doi.org/10.1002/art.38117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3969028PMC
November 2013

C-reactive protein exacerbates renal ischemia-reperfusion injury.

Am J Physiol Renal Physiol 2013 Jun 27;304(11):F1358-65. Epub 2013 Mar 27.

Department of Medicine, University of Alabama, Birmingham, AL, USA.

Renal ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury (AKI), occurring with hypotension and cardiovascular surgery and inevitably during kidney transplantation. Mortality from AKI is high due to incomplete knowledge of the pathogenesis of IRI and the lack of an effective therapy. Inflammation accompanies IRI and increases the blood level of C-reactive protein (CRP), a biomarker of worsened outcomes in AKI. To test if CRP is causal in AKI we subjected wild-type mice (WT) and human CRP transgenic mice (CRPtg) to bilateral renal IRI (both pedicles clamped for 30 min at 37°C then reperfused for 24 h). Serum human CRP level was increased approximately sixfold after IRI in CRPtg (10.62 ± 1.31 μg/ml at baseline vs. 72.01 ± 9.41 μg/ml at 24 h) but was not elevated by sham surgery wherein kidneys were manipulated but not clamped. Compared with WT, serum creatinine, urine albumin, and histological evidence of kidney damage were increased after IRI in CRPtg mice. RT-PCR analysis of mRNA isolated from whole kidneys of CRPtg and WT subjected to IRI revealed that in CRPtg kidneys 1) upregulation of markers of macrophage classical activation (M1 markers) was blunted, 2) downregulation of markers of macrophage alternative activation (M2 markers) was more robust, and 3) expression of the activating receptor FcγRI was increased. Our finding that CRP exacerbates IRI-induced AKI, perhaps by shifting the balance of macrophage activation and FcγR expression towards a detrimental portfolio, might make CRP a promising therapeutic target for the treatment of AKI.
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http://dx.doi.org/10.1152/ajprenal.00476.2012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3680688PMC
June 2013

Pneumococcal surface protein A inhibits complement deposition on the pneumococcal surface by competing with the binding of C-reactive protein to cell-surface phosphocholine.

J Immunol 2012 Dec 26;189(11):5327-35. Epub 2012 Oct 26.

Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 24294, USA.

In the presence of normal serum, complement component C3 is deposited on pneumococci primarily via the classical pathway. Pneumococcal surface protein A (PspA), a major virulence factor of pneumococci, effectively inhibits C3 deposition. PspA's C terminus has a choline-binding domain that anchors PspA to the phosphocholine (PC) moieties on the pneumococcal surface. C-reactive protein (CRP), another important host defense molecule, also binds to PC, and CRP binding to pneumococci enhances complement C3 deposition through the classical pathway. Using flow cytometry of PspA(+) and PspA(-) strains, we observed that the absence of PspA led to exposure of PC, enhanced the surface binding of CRP, and increased the deposition of C3. Moreover, when the PspA(-) mutant was incubated with a pneumococcal eluate containing native PspA, there was decreased deposition of CRP and C3 on the pneumococcal surface compared with incubation with an eluate from a PspA(-) strain. This inhibition was not observed when a recombinant PspA fragment, which lacks the choline-binding region of PspA, was added to the PspA(-) mutant. Also, there was much greater C3 deposition onto the PspA(-) pneumococcus when exposed to normal mouse serum from wild-type mice as compared with that from CRP knockout mice. Furthermore, when CRP knockout mouse serum was replenished with CRP, there was a dose-dependent increase in C3 deposition. The combined data reveal a novel mechanism of complement inhibition by a bacterial protein: inhibition of CRP surface binding and, thus, diminution of CRP-mediated complement deposition.
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http://dx.doi.org/10.4049/jimmunol.1201967DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3517878PMC
December 2012

Associations of C-Reactive Protein to Indices of Vascular Health and the Influence of Serum 25(OH)D Status in Healthy Adults.

J Nutr Metab 2012 16;2012:475975. Epub 2012 Sep 16.

Division of Pediatric Endocrinology and Metabolism, Department of Pediatrics, The Children's Hospital, University of Alabama at Birmingham, Birmingham, AL 35233, USA.

Unlabelled: Elevated serum high-sensitivity C-reactive protein (hs-CRP) and low serum 25-hydroxyvitamin D [25(OH)D] are associated with increased cardiovascular disease (CVD) risk. Ethnic differences in serum hs-CRP and 25(OH)D concentrations and CVD are known.

Objectives: to investigate the ethnic differences in hs-CRP concentrations, to assess the influence of 25(OH)D on these ethnic differences and to examine the influence of 25(OH)D on association between hs-CRP and cardiovascular health indices.

Subjects: 62 healthy adults [26 African Americans (AA), 26 European Americans (EA), and 10 Hispanic Americans (HA)], ages 18-55 years. Serum hs-CRP and 25(OH)D as well as pulse wave velocity (PWV), augmentation index (AIx), and flow-mediated dilatation (FMD) were measured. hs-CRP was inversely associated with 25(OH)D (r = -0.25, P = 0.049), and hs-CRP was positively associated with PWV (r = 0.29, P = 0.04). The association of hs-CRP with PWV attenuated after adjustment for 25(OH)D (P = 0.15). hs-CRP was higher in AA compared to EA (P = 0.05); this differences was reduced by 32% after adjusting for serum 25(OH)D.

Conclusion: eventhough the inverse association between serum 25(OH)D and CRP does not infer causality, lower serum 25(OH)D may increase risk for inflammation and endothelial dysfunction. The lower 25(OH)D in AA may predispose to greater inflammation and associated vascular dysfunction.
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http://dx.doi.org/10.1155/2012/475975DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3457628PMC
October 2012

Kidney injury accelerates cystogenesis via pathways modulated by heme oxygenase and complement.

J Am Soc Nephrol 2012 Jul 19;23(7):1161-71. Epub 2012 Apr 19.

Department of Medicine, University of Alabama at Birmingham, USA.

AKI accelerates cystogenesis. Because cystogenic mutations induce strong transcriptional responses similar to those seen after AKI, these responses may accelerate the progression of cystic renal disease. Here, we modulated the severity of the AKI-like response in Cys1(cpk/cpk) mice, a model that mimics autosomal recessive polycystic kidney disease. Specifically, we induced or inhibited activity of the renoprotective enzyme heme oxygenase (HO) and determined the effects on renal cystogenesis. We found that induction of HO attenuated both renal injury and the rate of cystogenesis, whereas inhibition of HO promoted cystogenesis. HO activity mediated the response of NFκB, which is a hallmark transcriptional feature common to both cystogenesis and AKI. Among the HO-modulated effects we measured, expression of complement component 3 (C3) strongly correlated with cystogenesis, a functionally relevant association as suggested by Cys1(cpk/cpk) mice with genetically induced C3 deficiency. Because both C3 deficiency and HO induction reduce cyst number and cyst areas, these two factors define an injury-stimulated cystogenic pathway that may provide therapeutic targets to slow the formation of new renal cysts and the growth of existing cysts.
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http://dx.doi.org/10.1681/ASN.2011050442DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3380643PMC
July 2012

A Selective Inhibitor of Human C-reactive Protein Translation Is Efficacious In Vitro and in C-reactive Protein Transgenic Mice and Humans.

Mol Ther Nucleic Acids 2012 Nov 13;1:e52. Epub 2012 Nov 13.

Department of Medicine, Division of Clinical Immunology and Rheumatology, The University of Alabama at Birmingham, Birmingham, Alabama, USA.

Observational studies of patients with established rheumatoid arthritis (RA) document a positive correlation between C-reactive protein (CRP) blood concentration and worsening of RA symptoms, but whether this association is causal or not is not known. Using CRP transgenic mice (CRPTg) with collagen-induced arthritis (CIA; a rodent model of RA), we explored causality by testing if CRP lowering via treatment with antisense oligonucleotides (ASOs) targeting human CRP mRNA was efficacious and of clinical benefit. We found that in CRPtg with established CIA, ASO-mediated lowering of blood human CRP levels improved the clinical signs of arthritis. In addition, in healthy human volunteers the ASO was well tolerated and efficacious i.e., treatment achieved significant CRP lowering. ASOs targeting CRP should provide a specific and effective way to lower human CRP levels, which might be an effective therapy in patients with established RA.Molecular Therapy - Nucleic Acids (2012) 1, e52; doi:10.1038/mtna.2012.44; published online 13 November 2012.
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http://dx.doi.org/10.1038/mtna.2012.44DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3511672PMC
November 2012

Biomarkers of inflammation and hemostasis associated with left ventricular mass: The Multiethnic Study of Atherosclerosis (MESA).

Int J Mol Epidemiol Genet 2011 28;2(4):391-400. Epub 2011 Nov 28.

Purpose: Biomarkers of inflammation and hemostasis have been associated with left ventricular (LV) mass. We studied relationships of C-reactive protein (CRP), interleukin-6 (IL6), D-dimer, soluble intercellular adhesion molecule-1 (sICAM-1), plasminogen activator inhibitor 1 (PAI-1), soluble thrombomodulin (sTM), soluble tumor necrosis factor type 1 receptor (sTNFR1), von Willebrand factor (vWF), soluble E-selectin (sE-selectin), factor VIII, fibrinogen, matrix metalloproteinase 3 (MMP3), and matrix metalloproteinase 9 (MMP9) with LV mass in an asymptomatic population. Multi-Ethnic Study of Atherosclerosis participants underwent magnetic resonance imaging to characterize LV mass; biomarkers were measured using standardized protocols (N = 763 to 4979). Adjusted models were used to associate each biomarker with LV mass while correcting for potential confounding.

Findings: LV mass was associated with many biomarkers after adjustment for demographic characteristics and traditional cardiovascular risk factors. Although the demographic and risk factor adjustments attenuated the association of CRP and IL6 with LV mass, further adjustment for weight changed regression coefficients from positive to negative for CRP and IL6 for LV mass. sTM, Factor VIII, and vWF were directly associated with LV mass in fully-adjusted models. For sTNFR1, sICAM-1, D-dimer, fibrinogen, and PAI-1, adjustment for risk factors and weight rendered associations with LV mass nonsignificant.

Conclusions: In this large cohort free of clinical cardiovascular disease, several hemostasis and inflammation markers were associated with LV mass. The unusual finding of a negative relationship of CRP and IL6 with LV mass only after adjustment for weight suggests that the effects of inflammation on LV mass are strongly influenced by obesity.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3243453PMC
October 2012

An about-face for C-reactive protein?

Clin Chem 2011 Oct 5;57(10):1351-3. Epub 2011 Aug 5.

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http://dx.doi.org/10.1373/clinchem.2011.172296DOI Listing
October 2011

Collagen-induced arthritis is exacerbated in C-reactive protein-deficient mice.

Arthritis Rheum 2011 Sep;63(9):2641-50

University of Alabama at Birmingham, Birmingham, AL 35294, USA.

Objective: Blood C-reactive protein (CRP) is routinely measured to gauge inflammation. In rheumatoid arthritis (RA), a heightened CRP level is predictive of a poor outcome, while a lowered CRP level is indicative of a positive response to therapy. CRP interacts with the innate and adaptive immune systems in ways that suggest it may be causal in RA and, although this is not proven, it is widely assumed that CRP makes a detrimental contribution to the disease process. Paradoxically, results from animal studies have indicated that CRP might be beneficial in RA. This study was undertaken to study the role of CRP in a mouse model of RA, the collagen-induced arthritis (CIA) model.

Methods: We compared the impact of CRP deficiency with that of transgenic overexpression of CRP on inflammatory and immune responses in mice, using CRP-deficient (Crp-/-) and human CRP-transgenic (CRP-Tg) mice, respectively. Susceptibility to CIA, a disease that resembles RA in humans, was compared between wild-type, Crp-/-, and CRP-Tg mice.

Results: CRP deficiency significantly altered the inflammatory cytokine response evoked by challenge with endotoxin or anti-CD3 antibody, and heightened some immune responses. Compared to that in wild-type mice, CIA in Crp-/- mice progressed more rapidly and was more severe, whereas CIA in CRP-Tg mice was dramatically attenuated. Despite these disparate clinical outcomes, anticollagen autoantibody responses during CIA did not differ among the genotypes.

Conclusion: CRP exerts an early and beneficial effect in mice with CIA. The mechanism of this effect remains unknown but does not involve improvement of the autoantibody profile. In humans, the presumed detrimental role of a heightened blood CRP level during active RA might be balanced by a beneficial effect of the baseline CRP (i.e., levels manifest during the preclinical stages of disease).
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http://dx.doi.org/10.1002/art.30444DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3168703PMC
September 2011

C-reactive protein promotes acute renal inflammation and fibrosis in unilateral ureteral obstructive nephropathy in mice.

Lab Invest 2011 Jun 7;91(6):837-51. Epub 2011 Mar 7.

Department of Medicine-Nephrology, West China Hospital of Sichuan University, Chengdu, China.

Elevated blood level of C-reactive protein (CRP) is associated with increased risk of chronic kidney disease. However, whether this association reflects functional importance of CRP in the pathogenesis of kidney disease remains unclear. In this study, we examined the biological role of CRP in a well-characterized model of progressive kidney disease, unilateral ureteral obstruction (UUO), in mice that express the human CRP gene (CRPtg). Compared with wild-type (Wt) mice at 3 days after UUO, CRPtg mice developed more severe renal inflammation with a significant increase in tubulointerstitial T cells and macrophages, upregulation of proinflammatory cytokines (IL-1β and TNF-α), chemokines (MCP-1), and adhesion molecules (ICAM-1). Renal fibrosis was also significantly enhanced in CRPtg mice as demonstrated by increased expression of tubulointerstitial α-smooth muscle actin and collagen types I and III compared with Wt mice. Interestingly, on days 7 and 14 after UUO, an equal severity of renal inflammation and fibrosis were observed in CRPtg and Wt mice. These findings suggested that CRP may have a role in the initiation of renal inflammation and fibrosis. Further study revealed that enhanced early renal inflammation and fibrosis on day 3 in CRPtg mice was associated with a significant upregulation of endogenous mouse CRP and FcγRI mRNA and increased activation of both NF-κB/p65 and TGF-β/Smad2/3 signaling, while equal severity of progressive renal injury at day 7 and day 14 between CRPtg and Wt mice were attributed to equivalent levels of CRP, FcγRI, phospho-NF-κB/p65, and TGF-β/Smad2/3 signaling. Based on these findings, we conclude that CRP may not only be a biomarker, but also a mediator in the early development of renal inflammation and fibrosis in a mouse model of UUO. Enhanced activation of both NF-κB and TGF-β/Smad signaling pathways may be mechanisms by which CRP promotes early renal inflammation and fibrosis.
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http://dx.doi.org/10.1038/labinvest.2011.42DOI Listing
June 2011

Inhibition of Experimental Autoimmune Encephalomyelitis in Human C-Reactive Protein Transgenic Mice Is FcγRIIB Dependent.

Autoimmune Dis 2010 Oct 12;2011:484936. Epub 2010 Oct 12.

Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, 1825 University Boulevard, SHEL 214, Birmingham, AL 35294-2182, USA.

We showed earlier that experimental autoimmune encephalomyelitis (EAE) in human C-reactive protein (CRP) transgenic mice (CRPtg) has delayed onset and reduced severity compared to wild-type mice. Since human CRP is known to engage Fc receptors and Fc receptors are known to play a role in EAE in the mouse, we sought to determine if FcγRI, FcγRIIb, or FcγRIII was needed to manifest human CRP-mediated protection of CRPtg. We report here that in CRPtg lacking either of the two activating receptors, FcγRI and FcγRIII, the beneficial effects of human CRP are still observed. In contrast, if CRPtg lack expression of the inhibitory receptor FcγRIIB, then the beneficial effect of human CRP is abrogated. Also, subcutaneous administration of purified human CRP stalled progression of ongoing EAE in wild-type mice, but similar treatment failed to impede EAE progression in mice lacking FcγRIIB. The results reveal that a CRP → FcγRIIB axis is responsible for protection against EAE in the CRPtg model.
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http://dx.doi.org/10.4061/2011/484936DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2989644PMC
October 2010

Complement receptor 1 expression on mouse erythrocytes mediates clearance of Streptococcus pneumoniae by immune adherence.

Infect Immun 2010 Jul 3;78(7):3129-35. Epub 2010 May 3.

Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.

Complement-containing immune complexes can be presented to phagocytes by human erythrocytes bearing complement receptor 1 (CR1). Although this has long been assumed to be a mechanism by which humans are able to protect themselves from "extracellular" bacteria such as pneumococci, there is little direct evidence. In these studies we have investigated this question by comparing results for erythrocytes from transgenic mice expressing human CR1 on their erythrocytes to the results for wild-type mouse erythrocytes that do not express CR1. We demonstrate that human CR1 expression on murine erythrocytes allows immune adherence to beads opsonized with either mouse or human serum as a source of complement. The role of CR1 in immune adherence was supported by studies showing that it was blocked by the addition of antibody to human CR1. Furthermore, human CR1 expression enhances the immune adherence of opsonized pneumococci to erythrocytes in vitro, and the pneumococci attached to erythrocytes via CR1 can be transferred in vitro to live macrophages. Even more importantly, we observed that if complement-opsonized pneumococci are injected intravenously with CR1(+) mouse erythrocytes into wild-type mice (after a short in vitro incubation), they are cleared faster than opsonized pneumococci similarly injected with wild-type mouse erythrocytes. Finally, we have shown that the intravenous (i.v.) injection of pneumococci into CR1(+) mice also results in more rapid blood clearance than in wild-type mice. These data support that immune adherence via CR1 on erythrocytes likely plays an important role in the clearance of opsonized bacteria from human blood.
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http://dx.doi.org/10.1128/IAI.01263-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2897369PMC
July 2010