Publications by authors named "Samira Kiani"

24 Publications

  • Page 1 of 1

The NIH Somatic Cell Genome Editing program.

Nature 2021 Apr 7;592(7853):195-204. Epub 2021 Apr 7.

McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, USA.

The move from reading to writing the human genome offers new opportunities to improve human health. The United States National Institutes of Health (NIH) Somatic Cell Genome Editing (SCGE) Consortium aims to accelerate the development of safer and more-effective methods to edit the genomes of disease-relevant somatic cells in patients, even in tissues that are difficult to reach. Here we discuss the consortium's plans to develop and benchmark approaches to induce and measure genome modifications, and to define downstream functional consequences of genome editing within human cells. Central to this effort is a rigorous and innovative approach that requires validation of the technology through third-party testing in small and large animals. New genome editors, delivery technologies and methods for tracking edited cells in vivo, as well as newly developed animal models and human biological systems, will be assembled-along with validated datasets-into an SCGE Toolkit, which will be disseminated widely to the biomedical research community. We visualize this toolkit-and the knowledge generated by its applications-as a means to accelerate the clinical development of new therapies for a wide range of conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41586-021-03191-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8026397PMC
April 2021

Multicellular Systems to Translate Somatic Cell Genome Editors to Humans.

Curr Opin Biomed Eng 2020 Dec 10;16:72-81. Epub 2020 Oct 10.

Department of Pathology, Division of Experimental Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.

As genome editors move into clinical trials, there is a need to establish multicellular systems to rapidly assess and predict toxic effects of genome editors in physiologically relevant human models. Advancements in organoid and organs-on-chip technologies offer the possibility to create multicellular systems that replicate the cellular composition and metabolic function of native tissues. Some multicellular systems have been validated in multiple applications for drug discovery and could be easily adapted to test genome editors; other models, especially those of the adaptive immune system, will require validation before being used as benchmarks for testing genome editors. Likewise, protocols to assess immunogenicity, to detect off-target effects, and to predict translation will need to be established and validated. This review will discuss key aspects to consider when designing, building, and/or adopting human multicellular systems for testing genome editors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cobme.2020.100249DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7948211PMC
December 2020

Gene Regulatory Network Analysis and Engineering Directs Development and Vascularization of Multilineage Human Liver Organoids.

Cell Syst 2021 Jan 7;12(1):41-55.e11. Epub 2020 Dec 7.

Department of Pathology, Division of Experimental Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA; Pittsburgh Liver Research Center, University of Pittsburgh, Pittsburgh, PA 15261, USA; School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85281, USA; Biodesign Institute, Arizona State University, Tempe, AZ 85281, USA; Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA; Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine and Science, Phoenix, AZ 85054, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA. Electronic address:

Pluripotent stem cell (PSC)-derived organoids have emerged as novel multicellular models of human tissue development but display immature phenotypes, aberrant tissue fates, and a limited subset of cells. Here, we demonstrate that integrated analysis and engineering of gene regulatory networks (GRNs) in PSC-derived multilineage human liver organoids direct maturation and vascular morphogenesis in vitro. Overexpression of PROX1 and ATF5, combined with targeted CRISPR-based transcriptional activation of endogenous CYP3A4, reprograms tissue GRNs and improves native liver functions, such as FXR signaling, CYP3A4 enzymatic activity, and stromal cell reactivity. The engineered tissues possess superior liver identity when compared with other PSC-derived liver organoids and show the presence of hepatocyte, biliary, endothelial, and stellate-like cell populations in single-cell RNA-seq analysis. Finally, they show hepatic functions when studied in vivo. Collectively, our approach provides an experimental framework to direct organogenesis in vitro by systematically probing molecular pathways and transcriptional networks that promote tissue development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cels.2020.11.002DOI Listing
January 2021

Reactions to the National Academies/Royal Society Report on .

CRISPR J 2020 10;3(5):332-349

In September 2020, a detailed report on was published. The report offers a translational pathway for the limited approval of germline editing under limited circumstances and assuming various criteria have been met. In this perspective, some three dozen experts from the fields of genome editing, medicine, bioethics, law, and related fields offer their candid reactions to the National Academies/Royal Society report, highlighting areas of support, omissions, disagreements, and priorities moving forward.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/crispr.2020.29106.manDOI Listing
October 2020

Synthetic immunomodulation with a CRISPR super-repressor in vivo.

Nat Cell Biol 2020 09 3;22(9):1143-1154. Epub 2020 Sep 3.

Pittsburgh Liver Research Center, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.

Transient modulation of the genes involved in immunity, without exerting a permanent change in the DNA code, can be an effective strategy to modulate the course of many inflammatory conditions. CRISPR-Cas9 technology represents a promising platform for achieving this goal. Truncation of guide RNA (gRNA) from the 5' end enables the application of a nuclease competent Cas9 protein for transcriptional modulation of genes, allowing multifunctionality of CRISPR. Here, we introduce an enhanced CRISPR-based transcriptional repressor to reprogram immune homeostasis in vivo. In this repressor system, two transcriptional repressors-heterochromatin protein 1 (HP1a) and Krüppel-associated box (KRAB)-are fused to the MS2 coat protein and subsequently recruited by gRNA aptamer binding to a nuclease competent CRISPR complex containing truncated gRNAs. With the enhanced repressor, we demonstrate transcriptional repression of the Myeloid differentiation primary response 88 (Myd88) gene in vitro and in vivo. We demonstrate that this strategy can efficiently downregulate Myd88 expression in lung, blood and bone marrow of Cas9 transgenic mice that receive systemic injection of adeno-associated virus (AAV)2/1-carrying truncated gRNAs targeting Myd88 and the MS2-HP1a-KRAB cassette. This downregulation is accompanied by changes in downstream signalling elements such as TNF-α and ICAM-1. Myd88 repression leads to a decrease in immunoglobulin G (IgG) production against AAV2/1 and AAV2/9 and this strategy modulates the IgG response against AAV cargos. It improves the efficiency of a subsequent AAV9/CRISPR treatment for repression of proprotein convertase subtilisin/kexin type 9 (PCSK9), a gene that, when repressed, can lower blood cholesterol levels. We also demonstrate that CRISPR-mediated Myd88 repression can act as a prophylactic measure against septicaemia in both Cas9 transgenic and C57BL/6J mice. When delivered by nanoparticles, this repressor can serve as a therapeutic modality to influence the course of septicaemia. Collectively, we report that CRISPR-mediated repression of endogenous Myd88 can effectively modulate the host immune response against AAV-mediated gene therapy and influence the course of septicaemia. The ability to control Myd88 transcript levels using a CRISPR-based synthetic repressor can be an effective strategy for AAV-based CRISPR therapies, as this pathway serves as a key node in the induction of humoral immunity against AAV serotypes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41556-020-0563-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7480217PMC
September 2020

A CRISPR Odyssey into Cancer Immunotherapy.

CRISPR J 2020 04;3(2):73-75

Pittsburgh Liver Research Center, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/crispr.2020.29090.edeDOI Listing
April 2020

Multifunctional CRISPR-Cas9 with engineered immunosilenced human T cell epitopes.

Nat Commun 2019 04 23;10(1):1842. Epub 2019 Apr 23.

Center for Personalized Diagnostics, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA.

The CRISPR-Cas9 system has raised hopes for developing personalized gene therapies for complex diseases. Its application for genetic and epigenetic therapies in humans raises concerns over immunogenicity of the bacterially derived Cas9 protein. Here we detect antibodies to Streptococcus pyogenes Cas9 (SpCas9) in at least 5% of 143 healthy individuals. We also report pre-existing human CD8+T cell immunity in the majority of healthy individuals screened. We identify two immunodominant SpCas9 T cell epitopes for HLA-A*02:01 using an enhanced prediction algorithm that incorporates T cell receptor contact residue hydrophobicity and HLA binding and evaluated them by T cell assays using healthy donor PBMCs. In a proof-of-principle study, we demonstrate that Cas9 protein can be modified to eliminate immunodominant epitopes through targeted mutation while preserving its function and specificity. Our study highlights the problem of pre-existing immunity against CRISPR-associated nucleases and offers a potential solution to mitigate the T cell immune response.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-019-09693-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6478683PMC
April 2019

Safe CRISPR: Challenges and Possible Solutions.

Trends Biotechnol 2019 04 21;37(4):389-401. Epub 2018 Oct 21.

School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, USA; www.kianilab.com. Electronic address:

Applications of CRISPR in human health and in gene drives are at the forefront of biological research as tools. This technology will affect humankind and our environment, so as this technology pushes forward, the design and implementation of safety measures is imperative. Novel technologies and forethought in various applications of CRISPR are essential for using this technology safely. Here, we review environmental and health-related safety concerns associated with using CRISPR and ways proposed to minimize risk.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.tibtech.2018.09.010DOI Listing
April 2019

Fluorescent Guide RNAs Facilitate Development of Layered Pol II-Driven CRISPR Circuits.

ACS Synth Biol 2018 08 31;7(8):1929-1936. Epub 2018 Jul 31.

School of Biological and Health Systems Engineering , Arizona State University , Tempe , Arizona 85281 , United States.

Efficient clustered regularly interspaced short palindromic repeat (CRISPR) guide RNA (gRNA) expression from RNA Polymerase II (Pol II) promoters will aid in construction of complex CRISPR-based synthetic gene networks. Yet, we require tools to properly visualize gRNA directly to quantitatively study the corresponding network behavior. To address this need, we employed a fluorescent gRNA (fgRNA) to visualize synthetic CRISPR network dynamics without affecting gRNA functionality. We show that studying gRNA dynamics directly enables circuit modification and improvement of network function in Pol II-driven CRISPR circuits. This approach generates information necessary for optimizing the overall function of these networks and provides insight into the hurdles remaining in Pol II-regulated gRNA expression.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acssynbio.8b00153DOI Listing
August 2018

An enhanced CRISPR repressor for targeted mammalian gene regulation.

Nat Methods 2018 08 16;15(8):611-616. Epub 2018 Jul 16.

Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA, USA.

The RNA-guided endonuclease Cas9 can be converted into a programmable transcriptional repressor, but inefficiencies in target-gene silencing have limited its utility. Here we describe an improved Cas9 repressor based on the C-terminal fusion of a rationally designed bipartite repressor domain, KRAB-MeCP2, to nuclease-dead Cas9. We demonstrate the system's superiority in silencing coding and noncoding genes, simultaneously repressing a series of target genes, improving the results of single and dual guide RNA library screens, and enabling new architectures of synthetic genetic circuits.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41592-018-0048-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6129399PMC
August 2018

Engineered CRISPR Systems for Next Generation Gene Therapies.

ACS Synth Biol 2017 09 7;6(9):1614-1626. Epub 2017 Jun 7.

School of Biological and Health Systems Engineering, Arizona State University , Tempe, Arizona 85281, United States.

An ideal in vivo gene therapy platform provides safe, reprogrammable, and precise strategies which modulate cell and tissue gene regulatory networks with a high temporal and spatial resolution. Clustered regularly interspaced short palindromic repeats (CRISPR), a bacterial adoptive immune system, and its CRISPR-associated protein 9 (Cas9), have gained attention for the ability to target and modify DNA sequences on demand with unprecedented flexibility and precision. The precision and programmability of Cas9 is derived from its complexation with a guide-RNA (gRNA) that is complementary to a desired genomic sequence. CRISPR systems open-up widespread applications including genetic disease modeling, functional screens, and synthetic gene regulation. The plausibility of in vivo genetic engineering using CRISPR has garnered significant traction as a next generation in vivo therapeutic. However, there are hurdles that need to be addressed before CRISPR-based strategies are fully implemented. Some key issues center on the controllability of the CRISPR platform, including minimizing genomic-off target effects and maximizing in vivo gene editing efficiency, in vivo cellular delivery, and spatial-temporal regulation. The modifiable components of CRISPR systems: Cas9 protein, gRNA, delivery platform, and the form of CRISPR system delivered (DNA, RNA, or ribonucleoprotein) have recently been engineered independently to design a better genome engineering toolbox. This review focuses on evaluating CRISPR potential as a next generation in vivo gene therapy platform and discusses bioengineering advancements that can address challenges associated with clinical translation of this emerging technology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acssynbio.7b00011DOI Listing
September 2017

Genetically engineering self-organization of human pluripotent stem cells into a liver bud-like tissue using Gata6.

Nat Commun 2016 Jan 6;7:10243. Epub 2016 Jan 6.

Department of Biological Engineering, Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts 02139, USA.

Human induced pluripotent stem cells (hiPSCs) have potential for personalized and regenerative medicine. While most of the methods using these cells have focused on deriving homogenous populations of specialized cells, there has been modest success in producing hiPSC-derived organotypic tissues or organoids. Here we present a novel approach for generating and then co-differentiating hiPSC-derived progenitors. With a genetically engineered pulse of GATA-binding protein 6 (GATA6) expression, we initiate rapid emergence of all three germ layers as a complex function of GATA6 expression levels and tissue context. Within 2 weeks we obtain a complex tissue that recapitulates early developmental processes and exhibits a liver bud-like phenotype, including haematopoietic and stromal cells as well as a neuronal niche. Collectively, our approach demonstrates derivation of complex tissues from hiPSCs using a single autologous hiPSCs as source and generates a range of stromal cells that co-develop with parenchymal cells to form tissues.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ncomms10243DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4729822PMC
January 2016

Cas9 gRNA engineering for genome editing, activation and repression.

Nat Methods 2015 Nov 7;12(11):1051-4. Epub 2015 Sep 7.

Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, USA.

We demonstrate that by altering the length of Cas9-associated guide RNA (gRNA) we were able to control Cas9 nuclease activity and simultaneously perform genome editing and transcriptional regulation with a single Cas9 protein. We exploited these principles to engineer mammalian synthetic circuits with combined transcriptional regulation and kill functions governed by a single multifunctional Cas9 protein.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nmeth.3580DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4666719PMC
November 2015

Highly efficient Cas9-mediated transcriptional programming.

Nat Methods 2015 Apr 2;12(4):326-8. Epub 2015 Mar 2.

1] Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, USA. [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA.

The RNA-guided nuclease Cas9 can be reengineered as a programmable transcription factor. However, modest levels of gene activation have limited potential applications. We describe an improved transcriptional regulator obtained through the rational design of a tripartite activator, VP64-p65-Rta (VPR), fused to nuclease-null Cas9. We demonstrate its utility in activating endogenous coding and noncoding genes, targeting several genes simultaneously and stimulating neuronal differentiation of human induced pluripotent stem cells (iPSCs).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nmeth.3312DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4393883PMC
April 2015

Accurate predictions of genetic circuit behavior from part characterization and modular composition.

ACS Synth Biol 2015 Jun 17;4(6):673-81. Epub 2014 Nov 17.

†Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.

A long-standing goal of synthetic biology is to rapidly engineer new regulatory circuits from simpler devices. As circuit complexity grows, it becomes increasingly important to guide design with quantitative models, but previous efforts have been hindered by lack of predictive accuracy. To address this, we developed Empirical Quantitative Incremental Prediction (EQuIP), a new method for accurate prediction of genetic regulatory network behavior from detailed characterizations of their components. In EQuIP, precisely calibrated time-series and dosage-response assays are used to construct hybrid phenotypic/mechanistic models of regulatory processes. This hybrid method ensures that model parameters match observable phenomena, using phenotypic formulation where current hypotheses about biological mechanisms do not agree closely with experimental observations. We demonstrate EQuIP's precision at predicting distributions of cell behaviors for six transcriptional cascades and three feed-forward circuits in mammalian cells. Our cascade predictions have only 1.6-fold mean error over a 261-fold mean range of fluorescence variation, owing primarily to calibrated measurements and piecewise-linear models. Predictions for three feed-forward circuits had a 2.0-fold mean error on a 333-fold mean range, further demonstrating that EQuIP can scale to more complex systems. Such accurate predictions will foster reliable forward engineering of complex biological circuits from libraries of standardized devices.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/sb500263bDOI Listing
June 2015

Human intestinal tissue with adult stem cell properties derived from pluripotent stem cells.

Stem Cell Reports 2014 Jun 3;2(6):838-52. Epub 2014 Jun 3.

Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3370, USA.

Genetically engineered human pluripotent stem cells (hPSCs) have been proposed as a source for transplantation therapies and are rapidly becoming valuable tools for human disease modeling. However, many applications are limited due to the lack of robust differentiation paradigms that allow for the isolation of defined functional tissues. Here, using an endogenous LGR5-GFP reporter, we derived adult stem cells from hPSCs that gave rise to functional human intestinal tissue comprising all major cell types of the intestine. Histological and functional analyses revealed that such human organoid cultures could be derived with high purity and with a composition and morphology similar to those of cultures obtained from human biopsies. Importantly, hPSC-derived organoids responded to the canonical signaling pathways that control self-renewal and differentiation in the adult human intestinal stem cell compartment. This adult stem cell system provides a platform for studying human intestinal disease in vitro using genetically engineered hPSCs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.stemcr.2014.05.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4050346PMC
June 2014

CRISPR transcriptional repression devices and layered circuits in mammalian cells.

Nat Methods 2014 Jul 5;11(7):723-6. Epub 2014 May 5.

1] Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. [2] Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. [3] Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.

A key obstacle to creating sophisticated genetic circuits has been the lack of scalable device libraries. Here we present a modular transcriptional repression architecture based on clustered regularly interspaced palindromic repeats (CRISPR) system and examine approaches for regulated expression of guide RNAs in human cells. Subsequently we demonstrate that CRISPR regulatory devices can be layered to create functional cascaded circuits, which provide a valuable toolbox for engineering purposes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nmeth.2969DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4228775PMC
July 2014

Genetic engineering of human pluripotent cells using TALE nucleases.

Nat Biotechnol 2011 Jul 7;29(8):731-4. Epub 2011 Jul 7.

The Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA.

Targeted genetic engineering of human pluripotent cells is a prerequisite for exploiting their full potential. Such genetic manipulations can be achieved using site-specific nucleases. Here we engineered transcription activator-like effector nucleases (TALENs) for five distinct genomic loci. At all loci tested we obtained human embryonic stem cell (ESC) and induced pluripotent stem cell (iPSC) clones carrying transgenic cassettes solely at the TALEN-specified location. Our data suggest that TALENs employing the specific architectures described here mediate site-specific genome modification in human pluripotent cells with similar efficiency and precision as do zinc-finger nucleases (ZFNs).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nbt.1927DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3152587PMC
July 2011

Alteration in male reproductive system in experimental cholestasis: roles for opioids and nitric oxide overproduction.

Eur J Pharmacol 2009 Aug 13;615(1-3):246-51. Epub 2009 May 13.

Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, P.O. Box 13145-784, Tehran, Iran.

Cirrhosis is associated with impairment of the male reproductive system, hypogonadism and feminization. It is important to rule out whether the impairment in the reproductive system exists earlier in the course of cholestatic liver disease to target effective therapies at the best time point. In this study we investigated the role of endogenous opioid and nitric oxide system in alterations of the reproductive system in male rats. We performed sham or bile duct ligation surgery on male Sprague-Dawley rats and treated the animals for seven days with saline, naltrexone, an opioid receptor blocker (20 mg/kg) and N (G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor (10 mg/kg). We then evaluated the plasma level of testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH), sperm count and motility as well as biomarkers of cholestasis and nitric oxide productions. The results showed that following cholestasis, total testosterone level decrease and LH level increase in plasma of cholestatic rats and treatment with L-NAME and naltrexone could improve the plasma level of testosterone. Naltrexone could decrease the elevated level of LH in cholestatic animals. In addition, the weight of seminal vesicles and prostate significantly decreased in cholestasis as compared to the control group and treatment with L-NAME and naltrexone could improve the weights of the two organs in cholestasis. Our results demonstrate for the first time that the male reproductive system is impaired early in cholestasis and that endogenous opioid and nitric oxide system contribute to these impairments in the early course of the disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ejphar.2009.04.049DOI Listing
August 2009

Opioid receptor blockade improves mesenteric responsiveness in biliary cirrhosis.

Dig Dis Sci 2008 Nov 9;53(11):3007-11. Epub 2008 May 9.

Department of Pharmacology, Tehran University of Medical Sciences, Tehran, Iran.

Arterial vasodilation with concomitant hyperdynamic circulation is a common finding in cirrhotic subjects. Elevated levels of plasma endogenous opioid peptides have been reported in cholestasis and cirrhosis. Increased opioid peptides contribute to different manifestations of chronic liver disease such as pruritus, ascitis, and hepatic encephalopathy. In this study the potential role of opioid system in cirrhosis-induced vascular hyporesponsiveness was investigated. Bile duct ligated and sham operated animals received daily subcutaneous administration of naltrexone, an opioid receptor antagonist (20 mg/kg/day), or saline for 28 days. After 4 weeks the superior mesenteric artery was cannulated and was perfused according to McGregor method and then phenylephrine vasoconstrictor response of mesenteric vessels (10(-10) to 10(-6 )mol) was examined. In order to evaluate the effects of acute opioid receptor blockade, additional groups of animals were treated by acute single intraperitoneal naltrexone injection (20 mg/kg). Plasma level of nitrite/nitrate as an indicator for nitric oxide production was measured. Biliary cirrhosis was accompanied with a decrease in baseline perfusion pressure in mesenteric vascular bed (P < 0.01). Chronic opioid receptor blockade significantly increased this parameter (P < 0.01). The maximum pressure response to phenylephrine was decreased significantly in cirrhosis while chronic naltrexone treatment completely improved it (P < 0.01). Acute single injection of naltrexone could not influence the understudied homodynamic parameters. Chronic opioid receptor blockade did not modulate the increased nitrite/nitrate levels following cholestasis. This study provided evidence on the contribution of endogenous opioid system to vascular hyporesponsiveness in cirrhosis which is not directly correlated to high plasma NO levels.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10620-008-0261-7DOI Listing
November 2008

Nitric oxide: a new concept in chronic sinusitis pathogenesis.

Am J Otolaryngol 2007 Sep-Oct;28(5):334-7

Iranian Rhinology Research Society, Department of Otorhinolaryngology, Head and Neck surgery & Otorhinolaryngology Research Center, Tehran University of Medical Sciences, Tehran, Iran.

Purpose: Exhaled NO is produced mainly in paranasal sinuses and nasal mucosa. Nasal NO has been suggested to have a variety of effects in nasal cavity. Decreased exhaled NO is found in chronic sinusitis, and NO metabolite levels are increased in animal models of chronic sinusitis, suggesting a role for them in sinusitis pathogenesis. There was no data available on human NO metabolite level.

Materials And Methods: We lavaged maxillary sinuses in a control and 2 patient groups. The control group was patients who underwent functional endoscopic sinus surgery (FESS) due to any other reason than chronic sinusitis. The patient groups had chronic rhinosinusitis with and without polyposis who underwent FESS. Maxillary sinuses were lavaged during FESS, and NO metabolites (nitrate and nitrite) were lavaged in the lavage fluid.

Results: Nitric oxide metabolite levels (mean +/- SEM) were 8.085 +/- 1.43 mumol/L in healthy maxillary sinus lavage fluid and 18.04 +/- 3.51 and 16.78 +/- 2.91 mumol/L in chronic rhinosinusitis with and without polyposis, respectively. Lavage fluid of sinuses with chronic sinusitis had elevated levels of NO metabolites, which were significantly higher than the control group. The difference between the chronic sinusitis with and without polyposis groups was not significant.

Conclusions: Nitric oxide metabolites were significantly higher in maxillary sinuses of patients with chronic sinusitis. Elevated levels of NO and NO metabolites in sinusitis might damage healthy sinus epithelium. NO metabolites may have an important role in sinusitis pathogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.amjoto.2006.10.014DOI Listing
January 2008

Opioid system blockade decreases collagenase activity and improves liver injury in a rat model of cholestasis.

J Gastroenterol Hepatol 2007 Mar;22(3):406-13

Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

Background: Following bile duct ligation (BDL) endogenous opioids accumulate in plasma and play a role in the pathophysiology and manifestation of cholestasis. Evidence of centrally mediated induction of liver injury by exogenous opioid agonist administration, prompts the question of whether opioid receptor blockade by naltrexone can affect cholestasis-induced liver injury.

Methods: Cholestasis was induced by BDL and cholestatic and sham-operated rats received either naltrexone or saline for 7 consecutive days. On the 7th day, liver samples were collected for determining matrix metalloproteinase-2 (MMP-2) activity, S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) content and blood samples were obtained for measuring plasma nitrite/nitrate and liver enzyme activities.

Results: Naltrexone-treated BDL animals had a significant reduction in plasma enzyme activity and nitrite/nitrate level. Liver SAM : SAH ratio and SAM level improved by naltrexone treatment in cholestatic animals compared to saline-treated BDL ones. Naltrexone treatment in BDL rats led to a decrease in the level of liver MMP-2 activity, which had already increased during cholestasis.

Conclusion: Opioid receptor blockade improved the degree of liver injury in cholestasis, as assessed by plasma enzyme and liver MMP-2 activities. The beneficial effect of naltrexone may be due to its ability to increase liver SAM level and restore the SAM : SAH ratio.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1440-1746.2006.04260.xDOI Listing
March 2007

The synergistic anticonvulsant effect of agmatine and morphine: possible role of alpha 2-adrenoceptors.

Epilepsy Res 2005 Jun;65(1-2):33-40

Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, P.O. Box 13145-784, Tehran, Iran.

Recent demonstrations of the anticonvulsant properties of agmatine suggest it may be considered as a potential adjunct for protection against seizure. We investigated the possibility of an additive anticonvulsant effect between low doses of agmatine and morphine. The thresholds for the clonic seizures induced by the intravenous administration of gamma-aminobutyric acid (GABA)-antagonist, pentylenetetrazole (PTZ) were assessed in mice. Morphine at lower doses (1-3mg/kg) increased and at higher doses (30, 60 mg/kg) decreased the seizure threshold. Pretreatment with a per se non-effective dose of agmatine (1mg/kg) potentiated the anticonvulsant effect of morphine. The combination of subeffective doses of agmatine and morphine led to potent anticonvulsant effects. The pro-convulsant effect of morphine was attenuated by agmatine. Yohimbine with a dose (1mg/kg) incapable of affecting seizure threshold reversed the effect of agmatine on both anticonvulsant and pro-convulsant effects of morphine. These results suggest that agmatine potentiates the anticonvulsant effect of morphine and alpha 2-adrenoceptors may be involved in this effect.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.eplepsyres.2005.04.003DOI Listing
June 2005

Homocysteine alterations in experimental cholestasis and its subsequent cirrhosis.

Life Sci 2005 Apr;76(21):2497-512

Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, P.O. Box 13145-784, Tehran, Iran.

Homocysteine (Hcy), an intermediate in methionine metabolism, has been proposed to be involved in hepatic fibrogenesis. Impaired liver function can alter Hcy metabolism. The aim of the present study was to determine plasma Hcy alterations in acute obstructive cholestasis and the subsequent biliary cirrhosis. Cholestasis was induced by bile duct ligation and sham-operated and unoperated rats were used as controls. The animals were studied on the days 7th, 14th, 21st and 28th after the operation. Plasma Hcy, cysteine, methionine, nitric oxide (NO) and liver S-adenosyl-methionine (SAM), S-adenosyl-homocysteine (SAH), SAM to SAH ratio and glutathione were measured. Chronic L-NAME treatment was also included in the study. Plasma Hcy concentrations were transiently elevated by the day 14th after bile duct ligation (P < 0.01) and subsequently returned to control levels. Similar relative fluctuations in plasma Hcy were observed in BDL rats after intraperitoneal methionine overload. Plasma methionine, cysteine and nitrite and nitrate were significantly increased after bile duct ligation. SAM to SAH ratio was diminished by the 1st week of cholestasis and remained significantly decreased throughout the study. These events were accompanied by a decrease in GSH to GSSG ratio in the liver. Chronic L-NAME treatment improved SAM to SAH ratio and prevented the elevation of plasma Hcy and methionine (P < 0.05) while couldn't influence the other parameters. In conclusion, this study demonstrates alterations in plasma Hcy and liver SAM and SAH contents in precirrhotic stages and in secondary biliary cirrhosis, for the first time. In addition, we observed that plasma Hcy concentrations in BDL rats follow a distinct pattern of alteration from what has been previously reported in other models of cirrhosis. NO overproduction may contribute to plasma Hcy elevation and liver SAM depletion after cholestasis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.lfs.2004.12.009DOI Listing
April 2005