Biomedical subjects

Muhammad M Yaqoob

Publications and source records attributed to Muhammad M Yaqoob.

28 records · Page 2Linked to original sources

PubMed2004

Post transplant T-cell lymphoma: a case series of four patients from a single unit and review of the literature.

Post-transplant lymphoproliferative disorders (PTLDs) occur in approximately 1% of renal graft recipients. Of these, up to 15 percent are of the T-cell type. In this study, we present four cases of T-cell lymphoma from our renal transplant population, each of whom presented with non-specific symptoms, pancytopenia and/or liver dysfunction, with no obvious lymphadenopathy. They were all diagnosed with rare subsets of T-cell PTLD that included hepato-splenic T-cell lymphoma and anaplastic large cell lymphoma (ALCL). At the time of presentation, the patients were too ill for treatment to be initiated and succumbed to their illness. Increased awareness of this condition may allow for earlier diagnosis and improve its prognosis.

Adult↗

PubMed2003

High glucose-induced oxidative stress causes apoptosis in proximal tubular epithelial cells and is mediated by multiple caspases.

Diabetic nephropathy is the leading cause of end-stage renal disease in the Western world. Poor glycemic control contributes to the development of diabetic nephropathy, but the mechanisms underlying high glucose-induced tissue injury are not fully understood. In the present study, the effect of high glucose on a proximal tubular epithelial cell (PTEC) line was investigated. Reactive oxygen species (ROS) were detected using the fluorescent probes dichlorofluorescein diacetate, dihydrorhodamine 123, and 2,3-diaminonapthalene. Peroxynitrite (ONOO-) generation and nitrite concentrations were increased after 24 h of high glucose treatment (P<0.05). LLC-PK1 cells exposed to high D-glucose (25 mM) for up to 48 h had increased DNA fragmentation (P<0.01), caspase-3 activity (P<0.001), and annexin-V staining (P<0.05) as well as decreased expression of XIAP when compared with controls (5 mM D-glucose). The ONOO- scavenger ebselen reduced DNA fragmentation and caspase-3 activity as well as the high glucose-induced nitrite production and DCF fluorescence. High glucose-induced DNA fragmentation was completely prevented by an inhibitor of caspase-3 (P<0.01) and a pan-caspase inhibitor (P<0.001). Caspase inhibition did not affect ROS generation. This study, in a PTEC line, demonstrates that high glucose causes the generation of ONOO-, leading to caspase-mediated apoptosis. Ebselen and a caspase-3 inhibitor provided significant protection against high glucose-mediated apoptosis, implicating ONOO- as a proapoptotic ROS in early diabetic nephropathy.

Animals↗

PubMed2003

Acute solvent exposure induced activation of cytochrome P4502E1 causes proximal tubular cell necrosis by oxidative stress.

Deliberate exposure to solvents has been associated with kidney disorders. However, the mechanism by which solvents induce renal damage after acute exposure has not been studied. Proximal tubular cell (LLC-PK1) cytotoxicity after exposure for 48 h to either 5 mM of p-xylene (XY) or toluene (TL) was compared to control (C) by cell viability (MTS assay), LDH release, DNA fragmentation, and malondialdehyde (MDA) release. CYP2E1 activity with or without a free radical scavenger (catalase-CT), or the CYP2E1 inhibitor disulfiram (DSF), was examined. Both p-xylene and toluene significantly reduced cell viability (XY 53.9 8+/-1.6 vs TL 54.8+/-0.9 vs C 102.7+/-2.1), increased CYP2E1 activity (mM/mg protein/min) (XY 3.6+/-0.5 vs TL 3.7+/-0.7 vs C 1.3+/-0.4) and MDA release (microM/mg protein) (XY 29.1+/-3.9 vs TL 12.3+/-1.4 vs C 2.8+/-0.3). LDH was increased (XY 59.9+/-3.0 vs TL 27.6+/-0.5 vs C 8.4+/-1.2), but there was no significant change in DNA fragmentation (OD/mg protein) suggesting necrosis as the predominant mode of cell death. DSF significantly attenuated CYP2E1 activity (XY+DSF 1.4+/-0.9, TL+DSF 2.3+/-0.1), LDH release (XY+DSF 45.1+/-2.0, TL+DSF 13.0+/-0.2) and MDA release (XY+DSF 4.3+/-0.5, TL+CT 6.2+/-1.1). Moreover, CT attenuated LDH release (XY+CT 36.4+/-5.1, TL+DSF 15.6+/-0.5) and MDA release (XY+DSF 5.4+/-0.7, TL+DSF 6.6+/-1.3) in XY and TL treated cells. This study confirms the pivotal role of CYP2E1 in solvent-induced oxidative stress and necrosis in proximal tubular cells after exposure to solvent at 5 mM for 48 h.

Cell Culture Techniques↗

PubMed2003

GW274150, a potent and highly selective inhibitor of iNOS, reduces experimental renal ischemia/reperfusion injury.

BACKGROUND: Generation of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) may contribute to renal ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the effects of GW274150, a novel, highly selective, potent and long-acting inhibitor of iNOS activity in rat and mouse models of renal I/R. METHODS: Rats were administered GW274150 (5 mg/kg intravenous bolus administered 30 minutes prior to I/R) and subjected to bilateral renal ischemia (45 minutes) followed by reperfusion (6 hours). Serum and urinary indicators of renal dysfunction, tubular and reperfusion injury were measured, specifically, serum urea, creatinine, aspartate aminotransferase (AST) and N-acetyl-beta-d-glucosaminidase (NAG) enzymuria. In addition, renal sections were used for histologic scoring of renal injury and for immunologic evidence of nitrotyrosine formation and poly [adenosine diphosphate (ADP)-ribose] (PAR). Nitrate levels were measured in rat plasma using the Griess assay. Mice (wild-type, administered 5 mg/kg GW274150, and iNOS-/-) were subjected to bilateral renal ischemia (30 minutes) followed by reperfusion (24 hours) after which renal dysfunction (serum urea, creatinine), renal myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels were measured. RESULTS: GW274150, administered prior to I/R, significantly reduced serum urea, serum creatinine, AST, and NAG indicating reduction of renal dysfunction and injury caused by I/R. GW274150 reduced histologic evidence of tubular injury and markedly reduced immunohistochemical evidence of nitrotyrosine and PAR formation, indicating reduced peroxynitrite formation and poly (ADP-ribose) polymerase (PARP) activation, respectively. GW274150 abolished the rise in the plasma levels of nitrate (indicating reduced NO production). GW274150 also reduced the renal dysfunction in wild-type mice to levels similar to that observed in iNOS-/- mice subjected to I/R. Renal MPO activity and MDA levels were significantly reduced in wild-type mice administered GW274150 and iNOS-/- mice subjected to renal I/R, indicating reduced polymorphonuclear leukocyte (PMN) infiltration and lipid peroxidation. CONCLUSIONS: These results suggest that (1). an enhanced formation of NO by iNOS contributes to the pathophysiology of renal I/R injury and (2). GW274150 reduces I/R injury of the kidney. We propose that selective inhibitors of iNOS activity may be useful against renal dysfunction and injury associated with I/R of the kidney.

Animals↗

PubMed2003

Calpain is activated in experimental uremia: is calpain a mediator of uremia-induced myocardial injury?

BACKGROUND: The cysteine proteases calpain and caspase-3 are known mediators of cell death. The aim of this study was to assess their contribution to the tissue damage found in experimental uremia. METHODS: Calpain and caspase-3 activities were measured in the hearts of rats that were sham-operated (control), sham-operated and spontaneously hypertensive (SHR), and those rendered uremic by 5/6 nephrectomy (uremic). In an in vitro study, heart myoblasts (Girardi) were incubated with human serum from healthy subjects (control serum conditioned media, CSCM) or uremic patients (uremic serum conditioned media, USCM), in the presence and absence of calpain and caspase-3 inhibitors. After 48 hours the activity of calpain and caspase-3 was measured, and cell injury determined by DNA fragmentation (ELISA) and lactate dehydrogenase (LDH) release. An in situ assay was designed to study how USCM affects calpain activity over time. RESULTS: In the in vivo study, mean calpain activities were almost identical in the control and SHR groups, but calpain and caspase-3 activities were much elevated in the uremic group (P < 0.01 and 0.001 respectively vs. control). The SHR group had significantly higher mean arterial blood pressure (P < 0.001 vs. control, 0.01 vs. uremic). In the in vitro study calpain activity and DNA fragmentation were markedly higher in USCM treated cells compared to CSCM (both P<0.05). Both were reduced in USCM cells containing calpain inhibitors (E64d, calpastatin, or PD 150606). LDH release was raised also in USCM treated cultures (P < 0.05), which only the E64d treatment could significantly reduce (P < 0.02). Caspase-3 activities were similar in USCM and CSCM groups. The in situ assay showed significant increases in calpain activity in USCM treated cells compared to CSCM after just 3.5 hours (P<0.01). CONCLUSIONS: In vivo results suggest that the increases in calpain and caspase-3 activity in uremic rat hearts were primarily due to uremia and not to hypertension. In vitro data demonstrate that uremia-induced cell injury can be attenuated by calpain inhibition. Therefore, it is likely that calpain is a mediator of uremia-induced myocardial injury.

Acrylates↗

PubMed2003

Calpain is a mediator of myocardial injury in experimental uremia: is it activated by endogenous ouabain?

BACKGROUND: Incidence of cardiovascular disease is more than 20-fold higher in patients with chronic renal failure than in aged-matched individuals with normal renal function. Little is understood about the causes or the mechanism of uremia-induced cardiovascular injury, but the involvement of calpain as a possible mediator has recently been under investigation. Mean calpain activity was found to be 3.4-fold higher in the hearts of uremic rats than in control or spontaneously hypertensive (SHR) rats. In addition, calpain activity was found to be stimulated in myoblasts (Girardi) treated with media enriched with uremic serum compared with cells treated with serum from healthy volunteers. In this study, we assessed the impact of calpain activation in uremia and explored the possibility that calpain might be activated in uremia by endogenous ouabain. Ouabain is known to be elevated in uremia and is strongly associated with left ventricular hypertrophy in essential hypertension. METHODS: Calpain activity was measured in situ in human-derived myoblasts treated with low doses of ouabain similar to those concentrations found in uremic patients. RESULTS: Low concentrations of ouabain (10 nmol/L) caused a highly significant increase in calpain activity, which could be completely inhibited by the simultaneous chelation of intracellular and extracellular Ca2+, and by the chelation of extracellular Ca2+ alone. CONCLUSIONS: Calpain activity can be stimulated by nanomolar concentrations of ouabain due to an influx of extracellular Ca2+. As circulating ouabain is known to be elevated in uremia and strongly associated with LVH remodeling, we hypothesize that endogenous ouabain might be one of the factors that facilitates the remodeling of the left ventricle in patients with renal failure.

Calpain↗

PubMed2003

Organic solvent-induced proximal tubular cell toxicity via caspase-3 activation.

BACKGROUND: Occupational exposure to solvents may be associated with development and progression of tubulo-interstitial fibrosis and chronic renal failure. However, the cellular mechanisms by which this occurs remain elusive. MATERIALS AND METHODS: The cytotoxicity of proximal tubular cells (LLC-PK1) exposed to 106 mg/mL of p-xylene or 92 mg/mL of toluene was compared with untreated controls using cell viability (MTS assay) and caspase-3 activity, with or without caspase-3 selective inhibitor. RESULTS: Both compounds reduced cell viability and increased caspase-3 activation (P < 0.005). Inhibition of caspase-3 by the selective inhibitor DEVD-CHO prevented injury (P < 0.001) and inhibited solvent-induced caspase-3 activation (P < 0.005). CONCLUSION: Inhibition of caspase-3, the critical caspase in the apoptosis process, prevents cell injury in LLC-PK1. This suggests that caspase-3 may play a pivotal role in solvent-induced proximal tubular cell injury.

Animals↗

PubMed2003

Increased platelet-monocyte aggregates and cardiovascular disease in end-stage renal failure patients.

BACKGROUND: Atherosclerotic cardiovascular disease is a major cause of morbidity and mortality in patients with end-stage renal disease. This excess morbidity cannot be entirely explained by well-recognized conventional and novel risk factors alone, and occurs irrespective of dialysis modality. Recent evidence suggests that the activation of platelets and their interaction with circulating cells are important independent risk factors for atherosclerosis in non-uraemic patients. We therefore studied platelet activation and circulating platelet-leucocyte aggregates in stable patients without evidence of cardiovascular disease on continuous ambulatory peritoneal dialysis (CAPD) and haemodialysis and investigated an association with cardiovascular events. METHODS: Immunofluorescent flow cytometry was used to measure the percentage of P-selectin- (CD62P) positive platelets, the percentage of platelet-neutrophil and platelet-monocyte aggregates, and the expression of the P-selectin ligand, P-selectin glycoprotein ligand-1 (PSGL-1, CD162) on leucocytes in haemodialysis and CAPD patients and normal controls. The platelet count and the mean platelet component (MPC, a measure of platelet activation) were determined on the ADVIATM 120 Haematology System (Bayer, NY). RESULTS: Platelet activation as assessed by MPC or CD62P expression was significantly increased in haemodialysis but not CAPD patients compared with controls. Circulating platelet-monocyte aggregates were significantly increased in parallel with a significant reduction in PSGL-1 expression on monocytes in both patient groups compared with normal controls. The presence of higher platelet-monocyte aggregates in dialysis patients was associated with increased cardiovascular events. CONCLUSION: We describe increased platelet-monocyte aggregates with reduced leucocyte PSGL-1 expression in patients with end-stage renal disease irrespective of dialysis modality, associated with an increased risk of cardiovascular disease. These findings may suggest a novel mechanism by which accelerated atherosclerosis occurs in uraemic patients.

Biomarkers↗

PubMed2002

Altered L-arginine metabolism results in increased nitric oxide release from uraemic endothelial cells.

Results regarding the nitric oxide (NO) system in uraemia are contradictory. L-arginine, the precursor of NO, is also metabolized by arginase to form ornithine and urea. In the present study, endothelial NO production and arginine metabolism in uraemia were assessed. In addition an in vivo model was used to examine excess consumption of NO in uraemia. NO and amino acid measurements were made from basal and stimulated (by bradykinin) uraemic and control endothelial cells. Reverse-transcriptase PCR was used to assess endothelial NO synthase (eNOS) and inducible NOS (iNOS) expression. Finally, aortae of uraemic rats were stained for nitrotyrosine (a marker of peroxynitrite). Basal uraemic cells produced more NO than the control cells. L-arginine levels were greater in uraemic (supernatants/cells), but ornithine levels were higher in control (supernatants/cells). Following stimulation, NO levels in supernatants were similar, but the rise in NO production was greater in control compared with uraemic cells; l-arginine levels still remained higher in uraemic supernatants/cells. Differences in ornithine concentration (supernatants/cells) disappeared following bradykinin stimulation, due to a rise in ornithine levels in the uraemic group. There was no difference in eNOS expression, nor was iNOS detected in either group. Only aortae from uraemic rats showed evidence for nitrotyrosine staining. These studies demonstrated increased basal NO release in uraemic endothelial cells, perhaps by inhibition of arginase and hence diversion of arginine to the NO pathway. The increased NO produced under basal conditions may be inactive due to excessive consumption, resulting in peroxynitrite formation. Interestingly, bradykinin appears to restore arginase activity in uraemia, resulting in normalization of NO production.

Adult↗

PubMedDate not supplied

Predictors of survival and technique success after reinsertion of peritoneal dialysis catheter following severe peritonitis.

BACKGROUND: Peritonitis remains the most important complication of peritoneal dialysis (PD). The success rate of restarting PD after severe peritonitis (peritonitis unresolved despite treatment with appropriate antibiotics for 3 days, or fungal or pseudomonas infections) is unclear. We wished to determine PD technique survival and overall mortality when PD is offered to these patients and to identify predictors of successful reinitiation. METHOD: We conducted a retrospective single-center study of 556 patients undergoing PD between January 2000 and December 2001. We collected demographic information from the 106 patients who had their PD catheter removed for peritonitis, details about their dialysis history and peritonitis, and whether they successfully restarted PD and if not, the reason. RESULTS: We divided patients into groups as follows: group 1 (n = 42) underwent catheter reinsertion, group 2 (n = 16) had no medical contraindication to restarting PD but the patients elected to remain on hemodialysis, group 3 (n = 35) were deemed medically unsuitable to return to PD, and group 4 (n = 13) were those that died within 4 weeks of presenting with peritonitis. If there were no medical contraindications, Indo-Asians were more likely to retry PD. In group 1, after a mean follow-up of 20 +/- 7.3 months, 23 of 42 patients restarted PD successfully. Technique survival for group 1 as a whole was 69% at 3 months and 55% at the end of follow-up. Patients of greater dialysis vintage were more likely to develop PD technique failure after restarting. Of those judged suitable for PD, there was no statistically significant difference in the mortality of patients who wished to either restart PD or remain on hemodialysis (group 1 vs group 2). Significant numbers of patients returned successfully to PD after pseudomonas and fungal peritonitis. CONCLUSION: Restarting PD after severe peritonitis was possible and safe. Ethnicity was an important predictor for wanting to retry PD, but not for technique failure: given the choice, Indo-Asians preferred PD and had a higher failure rate after restarting, but this did not reach statistical significance. Only dialysis vintage predicted technique failure. We conclude that, after severe peritonitis, patients should be given the choice to return to PD but risk stratification based on dialysis vintage is important. Patient retraining and creating a backup arteriovenous fistula might minimize morbidity in these high-risk patients.

Adolescent↗