Publications by authors named "Sumit Rawal"

11 Publications

  • Page 1 of 1

Thrombolysis and surgery for mitral prosthetic valve thrombosis: 11-year outcomes.

Asian Cardiovasc Thorac Ann 2019 Oct 14;27(8):633-640. Epub 2019 Sep 14.

Department of Cardiac Surgery, Institute of Cardiovascular Diseases, The Madras Medical Mission, Chennai, India.

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http://dx.doi.org/10.1177/0218492319878015DOI Listing
October 2019

Evaluation of the efficiency of tumor and tissue delivery of carrier-mediated agents (CMA) and small molecule (SM) agents in mice using a novel pharmacokinetic (PK) metric: relative distribution index over time (RDI-OT).

J Nanopart Res 2014 Nov;16(11)

Division of Pharmacotherapy and Experimental Therapeutics, University of North Carolina at Chapel Hill (UNC) Eshelman School of Pharmacy, 120 Mason Farm Road, Suite 1013, CB 7361, Chapel Hill, NC 27599-7361, USA.

The pharmacokinetics (PK) of carrier-mediated agents (CMA) is dependent upon the carrier system. As a result, CMA PK differs greatly from the PK of small molecule (SM) drugs. Advantages of CMAs over SMs include prolonged circulation time in plasma, increased delivery to tumors, increased antitumor response, and decreased toxicity. In theory, CMAs provide greater tumor drug delivery than SMs due to their prolonged plasma circulation time. We sought to create a novel PK metric to evaluate the efficiency of tumor and tissue delivery of CMAs and SMs. We conducted a study evaluating the plasma, tumor, liver, and spleen PK of CMAs and SMs in mice bearing subcutaneous flank tumors using standard PK parameters and a novel PK metric entitled relative distribution over time (RDI-OT), which measures efficiency of delivery. RDI-OT is defined as the ratio of tissue drug concentration to plasma drug concentration at each time point. The standard concentration versus time area under the curve values (AUC) of CMAs were higher in all tissues and plasma compared with SMs. However, 8 of 17 SMs had greater tumor RDI-OT AUC values than their CMA comparators and all SMs had greater tumor RDI-OT AUC values than their CMA comparators. Our results indicate that in mice bearing flank tumor xenografts, SMs distribute into tumor more efficiently than CMAs. Further research in additional tumor models that may more closely resemble tumors seen in patients is needed to determine if our results are consistent in different model systems.
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http://dx.doi.org/10.1007/s11051-014-2662-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4574509PMC
November 2014

Modulation of the spleen transcriptome in domestic turkey (Meleagris gallopavo) in response to aflatoxin B1 and probiotics.

Immunogenetics 2015 Mar 20;67(3):163-78. Epub 2015 Jan 20.

Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 295 AS/VM, 1988 Fitch Ave., St. Paul, MN, 55108, USA.

Poultry are highly susceptible to the immunotoxic effects of the food-borne mycotoxin aflatoxin B1 (AFB1). Exposure impairs cell-mediated and humoral immunity, limits vaccine efficacy, and increases the incidence of costly secondary infections. We investigated the molecular mechanisms of AFB1 immunotoxicity and the ability of a Lactobacillus-based probiotic to protect against aflatoxicosis in the domestic turkey (Meleagris gallopavo). The spleen transcriptome was examined by RNA sequencing (RNA-seq) of 12 individuals representing four treatment groups. Sequences (6.9 Gb) were de novo assembled to produce over 270,000 predicted transcripts and transcript fragments. Differential expression analysis identified 982 transcripts with statistical significance in at least one comparison between treatment groups. Transcripts with known immune functions comprised 27.6 % of significant expression changes in the AFB1-exposed group. Short exposure to AFB1 suppressed innate immune transcripts, especially from antimicrobial genes, but increased the expression of transcripts from E3 ubiquitin-protein ligase CBL-B and multiple interleukin-2 response genes. Up-regulation of transcripts from lymphotactin, granzyme A, and perforin 1 could indicate either increased cytotoxic potential or activation-induced cell death in the spleen during aflatoxicosis. Supplementation with probiotics was found to ameliorate AFB1-induced expression changes for multiple transcripts from antimicrobial and IL-2-response genes. However, probiotics had an overall suppressive effect on immune-related transcripts.
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http://dx.doi.org/10.1007/s00251-014-0825-yDOI Listing
March 2015

Aflatoxicosis chemoprevention by probiotic Lactobacillius and lack of effect on the major histocompatibility complex.

Res Vet Sci 2014 Oct 13;97(2):274-81. Epub 2014 Jun 13.

Graduate Toxicology Program, and Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, UT 84322, USA. Electronic address:

Turkeys are extremely sensitive to aflatoxin B1 (AFB1) which causes decreased growth, immunosuppression and liver necrosis. The purpose of this study was to determine whether probiotic Lactobacillus, shown to be protective in animal and clinical studies, would likewise confer protection in turkeys, which were treated for 11 days with either AFB1 (AFB; 1 ppm in diet), probiotic (PB; 1 × 10(11) CFU/ml; oral, daily), probiotic + AFB1 (PBAFB), or PBS control (CNTL). The AFB1 induced drop in body and liver weights were restored to normal in CNTL and PBAFB groups. Hepatotoxicity markers were not significantly reduced by probiotic treatment. Major histocompatibility complex (MHC) genes BG1 and BG4, which are differentially expressed in liver and spleens, were not significantly affected by treatments. These data indicate modest protection, but the relatively high dietary AFB1 treatment, and the extreme sensitivity of this species may reveal limits of probiotic-based protection strategies.
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http://dx.doi.org/10.1016/j.rvsc.2014.06.008DOI Listing
October 2014

Response of the hepatic transcriptome to aflatoxin B1 in domestic turkey (Meleagris gallopavo).

PLoS One 2014 30;9(6):e100930. Epub 2014 Jun 30.

Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, Minnesota, United States of America.

Dietary exposure to aflatoxin B1 (AFB1) is detrimental to avian health and leads to major economic losses for the poultry industry. AFB1 is especially hepatotoxic in domestic turkeys (Meleagris gallopavo), since these birds are unable to detoxify AFB1 by glutathione-conjugation. The impacts of AFB1 on the turkey hepatic transcriptome and the potential protection from pretreatment with a Lactobacillus-based probiotic mixture were investigated through RNA-sequencing. Animals were divided into four treatment groups and RNA was subsequently recovered from liver samples. Four pooled RNA-seq libraries were sequenced to produce over 322 M reads totaling 13.8 Gb of sequence. Approximately 170,000 predicted transcripts were de novo assembled, of which 803 had significant differential expression in at least one pair-wise comparison between treatment groups. Functional analysis linked many of the transcripts significantly affected by AFB1 exposure to cancer, apoptosis, the cell cycle or lipid regulation. Most notable were transcripts from the genes encoding E3 ubiquitin-protein ligase Mdm2, osteopontin, S-adenosylmethionine synthase isoform type-2, and lipoprotein lipase. Expression was modulated by the probiotics, but treatment did not completely mitigate the effects of AFB1. Genes identified through transcriptome analysis provide candidates for further study of AFB1 toxicity and targets for efforts to improve the health of domestic turkeys exposed to AFB1.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0100930PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4076218PMC
February 2015

Pharmacokinetics and efficacy of PEGylated liposomal doxorubicin in an intracranial model of breast cancer.

PLoS One 2013 1;8(5):e61359. Epub 2013 May 1.

Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.

Introduction: Breast cancer brain metastases (BCBM) are a challenging consequence of advanced BC. Nanoparticle agents, including liposomes, have shown enhanced delivery to solid tumors and brain. We compared pharmacokinetics (PK) and efficacy of PEGylated liposomal doxorubicin (PLD) with non-liposomal doxorubicin (NonL-doxo) in an intracranial model of BC.

Methods: Athymic mice were inoculated intracerebrally with MDA-MB-231-BR-luciferase-expressing cells. Tumor-bearing mice were administered PLD or NonL-doxo at 6 mg/kg IV × 1 and were euthanized prior to and 0.083, 1, 3, 6, 24, 72 and 96 h post-treatment. Samples were processed to measure sum total doxorubicin via HPLC. PLD and NonL-doxo were administered IV weekly as single agents (6 mg/kg) or in combination (4.5 mg/kg) with the PARP inhibitor, ABT-888, PO 25 mg/kg/day. Efficacy was assessed by survival and bioluminescence.

Results: Treatment with PLD resulted in approximately 1,500-fold higher plasma and 20-fold higher intracranial tumor sum total doxorubicin AUC compared with NonL-doxo. PLD was detected at 96 h; NonL-doxo was undetectable after 24 h in plasma and tumor. Median survival of PLD-treated animals was 32 days (d, [CI] 31-38), which was significantly longer than controls (26d [CI 25-28]; p = 0.0012) or NonL-doxo treatment (23.5d [CI 18-28], p = 0.0002). Combination treatment with PLD/ABT-888 yielded improved survival compared to NonL-doxo/ABT-888 (35d [CI 31-38] versus 29.5d [CI 25-34]; p = 0.006).

Conclusions: PLD provides both PK and efficacy advantage over NonL-doxo in the treatment of an in vivo model of BCBM. The results provide preclinical rationale to translate findings into early phase trials of PLD, with or without ABT-888, for patients with BCBM.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0061359PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3641071PMC
November 2013

Plasma, tumor and tissue pharmacokinetics of Docetaxel delivered via nanoparticles of different sizes and shapes in mice bearing SKOV-3 human ovarian carcinoma xenograft.

Nanomedicine 2013 Jul 6;9(5):686-93. Epub 2012 Dec 6.

Department of Pharmaceutical Sciences, University of North Carolina, Chapel Hill, NC 27599, USA.

Unlabelled: The particle fabrication technique PRINT® was used to fabricate monodisperse size and shape specific poly(lactide-co-glycolide) particles loaded with the chemotherapeutic Docetaxel. The pharmacokinetics of two cylindrical shaped particles with diameter=80nm; height=320nm (PRINT-Doc-80×320) and d=200nm; h=200nm (PRINT-Doc-200×200) were compared to Docetaxel in mice bearing human ovarian carcinoma SKOV-3 flank xenografts. The Docetaxel plasma exposure was ~20-fold higher for both particles compared to docetaxel. Additionally, the volume of distribution (Vd) of Docetaxel in PRINT formulations was ~18-fold (PRINT-Doc-80×320) and ~33-fold (PRINT-Doc-200×200) lower than Docetaxel. The prolonged duration of Docetaxel in plasma when dosed with PRINT formulations subsequently led to increased tumor exposure of Docetaxel from 0 to 168h (~53% higher for PRINT-Doc-80×320 and ~76% higher for PRINT-Doc-200×200 particles). PRINT-Doc-80×320 had lower exposures in the liver, spleen and lung compared with PRINT-Doc-200×200. Thus, the use of particles with smaller feature size may be preferred to decrease clearance by organs of the mononuclear phagocyte system.

From The Clinical Editor: In this study, the plasma, tumor, and tissue pharmacokinetics of different Docetaxel nanoparticles of precise shape and size were characterized in mice with human ovarian carcinoma xenograft. It is concluded that the use of particles with smaller feature size may be preferred to decrease clearance by organs of the mononuclear phagocyte system.
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http://dx.doi.org/10.1016/j.nano.2012.11.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3706026PMC
July 2013

Pharmacokinetics and antitumor efficacy of XMT-1001, a novel, polymeric topoisomerase I inhibitor, in mice bearing HT-29 human colon carcinoma xenografts.

Clin Cancer Res 2012 May 5;18(9):2591-602. Epub 2012 Mar 5.

Division of Pharmacotherapy & Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, USA.

Purpose: To evaluate the pharmacokinetics and tissue disposition of macromolecular camptothecin (CPT) drug conjugate, XMT-1001, and irinotecan (CPT-11) in mice bearing HT-29 xenograft tumors.

Experimental Design: The antitumor efficacy of XMT-1001 was evaluated in the mouse HT-29 human colon carcinoma xenograft model. XMT-1001 was administered intravenously to female athymic nude (nu/nu) mice bearing established HT-29 xenograft tumors (n = 10) at 15, 30, and 60 mg CPT equivalents/kg on weekly or biweekly schedules. The tumor growth inhibition and tumor growth delay endpoints were used for efficacy evaluation. In the pharmacokinetic study, XMT-1001 was administered intravenously at a pharmacologically relevant dose of 60 mg CPT equivalents/kg × 1 via tail vein or an equimolar dose of CPT-11 at 100 mg/kg i.p. × 1. Mice (n = 3 per time point) were euthanized from 0.083 to 336 hours after XMT-1001 administration and from 0.083 to 24 hours after CPT-11. Plasma, tumor, and tissues were collected from all animals. A liquid chromatography-tandem mass spectrometry assay was used to measure XMT-1001, conjugate release products, CPT-20-O-(N-succinimido-glycinate; CPT-SI) and CPT-20-O-(N-succinamidoyl-glycinate; CPT-SA), and CPT.

Results: After XMT-1001 administration, the majority of the plasma exposure is accounted for by conjugated CPT. XMT-1001 exhibited a prolonged exposure of conjugated drug, active conjugate primary release products, CPT-SI and CPT-SA, and active CPT, which was associated with greater antitumor response compared with CPT-11.

Conclusions: XMT-1001 provides an extended systemic and tumor exposure of conjugated drug and shows improved antitumor effect compared with CPT-11.
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http://dx.doi.org/10.1158/1078-0432.CCR-11-1554DOI Listing
May 2012

Metabolism of aflatoxin B1 in turkey liver microsomes: the relative roles of cytochromes P450 1A5 and 3A37.

Toxicol Appl Pharmacol 2011 Aug 18;254(3):349-54. Epub 2011 May 18.

Graduate Toxicology Program, and Department of Veterinary Sciences, School of Veterinary Medicine, Utah State University, Logan, UT 84322, USA.

The extreme sensitivity of turkeys to aflatoxin B(1) (AFB(1)) is associated with efficient epoxidation by hepatic cytochromes P450 (P450) 1A5 and 3A37 to exo-aflatoxin B(1)-8,9-epoxide (exo-AFBO). The combined presence of 1A5 and 3A37, which obey different kinetic models, both of which metabolize AFB(1) to the exo-AFBO and to detoxification products aflatoxin M(1) (AFM(1)) and aflatoxin Q(1) (AFQ(1)), respectively, complicates the kinetic analysis of AFB(1) in turkey liver microsomes (TLMs). Antisera directed against 1A5 and 3A37, thereby individually removing the catalytic contribution of these enzymes, were used to identify the P450 responsible for epoxidating AFB(1) in TLMs. In control TLMs, AFB(1) was converted to exo-AFBO in addition to AFM(1) and AFQ(1) confirming the presence of functional 1A5 and 3A37. Pretreatment with anti-1A5 inhibited exo-AFBO formation, especially at low, submicromolar (~0.1μM), while anti-3A37, resulted in inhibition of exo-AFBO formation, but at higher (>50μM) AFB(1) concentrations. Metabolism in immunoinhibited TLMs resembled that of individual enzymes: 1A5 produced exo-AFBO and AFM(1), conforming to Michaelis-Menten, while 3A37 produced exo-AFBO and AFQ(1) following the kinetic Hill equation. At 0.1μM AFB(1), close to concentrations in livers of exposed animals, 1A5 contributed to 98% of the total exo-AFBO formation. At this concentration, 1A5 accounted for a higher activation:detoxification (50:1, exo-AFBO: AFM(1)) compared to 3A37 (0.15: 1, exo-AFBO: AFQ(1)), suggesting that 1A5 is high, while 3A4 is the low affinity enzyme in turkey liver. The data support the conclusion that P450 1A5 is the dominant enzyme responsible for AFB(1) bioactivation and metabolism at environmentally-relevant AFB(1) concentrations in turkey liver.
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http://dx.doi.org/10.1016/j.taap.2011.05.010DOI Listing
August 2011

Cloning, expression and functional characterization of cytochrome P450 3A37 from turkey liver with high aflatoxin B1 epoxidation activity.

Chem Res Toxicol 2010 Aug;23(8):1322-9

Department of Veterinary Sciences, Graduate Program in Toxicology, Utah State University, Logan, UT 84322-4620, USA.

Cytochrome P450s (P450) play an important role in the formation of carcinogenic and mutagenic electrophilic intermediates from a wide range of xenobiotics, including naturally occurring dietary compounds. The pathogenesis of hepatotoxic and hepatocarcinogenic action of the mycotoxin aflatoxin B(1) (AFB(1)) involves initial bioactivation by P450s to a reactive and electrophilic intermediate exo-aflatoxin B(1)-8,9-epoxide (exo-AFBO). Poultry, especially turkeys are extremely sensitive to AFB(1), a condition due, in part, to efficient epoxidation by P450 1A and 3A enzymes. We previously reported the discovery of P450 1A5 from turkey liver, which like its human homologue, 1A2, bioactivated AFB(1) to exo-AFBO and aflatoxin M(1) (AFM(1)). Here, we describe P450 3A37, the 3A4 homologue from turkey liver. This gene has an open reading frame (ORF) of 1512 bp, and the protein is predicted to be 504 amino acids with 97% identity to chicken P450 3A37. A truncated construct of the turkey P450 3A37 gene with 11 amino acids deleted from the hydrophobic N-terminal region was heterologously expressed in Escherichia coli, the protein from which exhibited a CO difference spectrum typical of P450s. Like human P450 3A4, 3A37 biotransformed AFB(1) to exo-AFBO and aflatoxin Q(1) (AFQ(1)) and possessed nifedipine oxidation activity, both of which were inhibited by the P450 3A4 inhibitor 17alpha-ethynylestradiol. Oxidation of AFB(1) to exo-AFBO and AFQ(1) by P450 3A37 followed sigmoidal Hill kinetics, suggestive of an allosteric interaction between the enzyme and AFB(1). The Hill coefficient (n) value was 1.9 for exo-AFBO and 1.6 for AFQ(1), indicative of positive cooperativity. The calculated K(m) and V(max) values for the formation of exo-AFBO were 287 +/- 21 muM and 1.45 +/- 0.07 nmol/min/nmol P450, respectively, whereas those of AFQ(1) formation were 302 +/- 51 muM and 7.86 +/- 0.75 nmol/min/nmol P450, respectively. These data strongly suggest that P450 3A37, along with P450 1A5, plays an important role in AFB(1) epoxidation in turkey liver.
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http://dx.doi.org/10.1021/tx1000267DOI Listing
August 2010

Aflatoxin B1 in poultry: toxicology, metabolism and prevention.

Res Vet Sci 2010 Dec 11;89(3):325-31. Epub 2010 May 11.

Graduate Program in Toxicology, Department of Veterinary Sciences, Utah State University, Logan, UT 84322-4620, USA.

Aflatoxins (AF) are ubiquitous in corn-based animal feed and causes hepatotoxic and hepatocarcinogenic effects. The most important AF in terms of toxic potency and occurrence is aflatoxin B1 (AFB1). Poultry, especially turkeys, are extremely sensitive to the toxic and carcinogenic action of AFB1, resulting in millions of dollars in annual losses to producers due to reduced growth rate, increased susceptibility to disease, reduced egg production and other adverse effects. The extreme sensitivity of turkeys and other poultry to AFB1 is associated with efficient hepatic cytochrome P450-mediated bioactivation and deficient detoxification by glutathione S-transferases (GST). Discerning the biochemical and molecular mechanisms of this extreme sensitivity of poultry to AFB1, will contribute in the development of novel strategies to increase aflatoxin resistance. Since AFB1 is an unavoidable contaminant of corn-based poultry feed, chemoprevention strategies aimed at reducing AFB1 toxicity in poultry and in other animals have been the subject of numerous studies. This brief review summarizes many of the key recent findings regarding the action of aflatoxins in poultry.
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http://dx.doi.org/10.1016/j.rvsc.2010.04.011DOI Listing
December 2010