Increased nitrotyrosine staining in kidneys from patients with diabetic nephropathy

BACKGROUND: Proximal tubular cells produce nitric oxide (NO.). We have shown that under hyperglycemic conditions, cultured proximal tubular cells express cytochrome P450 2E1, which is capable of producing superoxide (O2.). NO. and O2. react to form peroxynitrite (ONOO.), a powerful oxidant. ONOO. nitrosylates tyrosine moieties on proteins causing tissue damage. Our hypothesis is that ONOO. plays a role in early diabetic tubular damage and perhaps disease progression. METHODS: Renal biopsies from patients with diabetic nephropathy (DM), acute allograft rejection (AAR), acute allograft tubular necrosis (ATN), and glomerulonephritis (GN) were obtained. Normal kidney specimens were taken from nephrectomy samples (N = 10 for each group). The tissues were examined for the presence of nitrotyrosine using an immunoperoxidase technique with a polyclonal antibody. Samples were then arbitrarily scored, and the results analyzed (analysis of variance and Student's t-test for unpaired data). The number of apoptotic cells in a sample of tubules in each biopsy was also assessed. RESULTS: The DM biopsies showed increased staining for nitrotyrosine in proximal tubules (P = 0.0001) and in the thin limb of the loop of Henle (P = 0.0006) compared with all other groups. There was increased staining in the ascending and distal tubules in GN as compared to DM and ATN (P = 0.01). Nitrotyrosine was also found in all distal tubules and collecting ducts, including normals. There was no difference in the number of apoptotic tubular cells in diabetics compared with controls. CONCLUSION: To our knowledge, these data provide the first evidence for the presence of nitrotyrosine in both normal and diseased kidneys. The significance of the findings in normals is unclear, but could be due to activation of constitutive NOS. However, the study clearly demonstrates increased production of ONOO. in proximal tubules of patients with DM, and suggests that oxidant injury of the proximal tubules plays an important part in the pathogenesis of DM.     

Literature Review of Passenger Lymphocyte Syndrome Following Renal Transplantation and Two Case Reports

Passenger lymphocyte syndrome (PLS) is an immune‐mediated hemolysis. It occurs following ABO blood group mismatched solid organ and/or bone marrow transplantation between donor and recipient. We report two cases of PLS occurring after renal transplantation. Both recipients received live related kidney transplants; one from his mother and the other from his brother. The direction of blood group transfer, from donor to recipient, was O Rh D+ to A Rh D+ in both cases. Approximately 12 days after transplantation, both recipients showed a rapid fall in their hemoglobin levels with no identifiable bleeding source. DAT positive hemolysis was confirmed and anti‐A antibodies were detected in recipient sera, confirming a diagnosis of PLS. Both cases required blood transfusion support to maintain their hemoglobin and both had good renal outcomes. We have identified 99 PLS cases following renal transplant in the English literature. Previous ABO sensitization, donor blood group O to recipient blood group A or B transfer, and ciclosporin treatment have been identified as risk factors for PLS. Clinical outcomes in general are good; nonetheless, cases of graft failure and deaths have been reported. Early diagnosis and appropriate treatment are important in at risk individuals.     

Distinct role of MAPKAPK-2 in the regulation of TNF gene expression by Toll-like receptor 7 and 9 ligands

Toll-like receptor ligands (TLRLs) produced by various pathogens activate mitogen-activated protein kinases (MAPKs). While the dependence on p38 MAPK activation for the induction of inflammatory genes by the TLR4L, lipopolysaccharide (LPS), has been well documented, the importance of the p38 pathway in gene regulation by other TLRLs is less well understood. We have focused our analysis on two TLRLs with therapeutic potential, imidazoquinoline S28463 (TLR7L) and CpG DNA (TLR9L), to explore in detail their effects on the regulation of gene expression in macrophages. Here we report that activation of the p38 MAPK/MK2 pathway is crucial for both S28463- and CpG-induced cytokine and chemokine production. We show that the stability of TNF mRNA induced by CpG DNA and S28463 is not dependent on the p38 MAPK/MK2 pathway, in contrast to LPS-induced TNF mRNA. Using a GFP reporter construct under the control of the 3' untranslated region of the TNF gene, we demonstrate that S28463 and CpG DNA-induced MK2 signalling regulates TNF mRNA primarily at the translational level, whereas LPS-induced MK2 signalling regulates both the stability and translational efficiency of TNF mRNA. Overall, these data provide insight into distinct molecular mechanisms of gene expression regulation by different Toll-like receptor ligands.     

A randomised comparison of simvastatin versus simvastatin and low cholesterol diet in the treatment of hypercholesterolaemia

There is little evidence to show that strict dietary modification alone confers any significant impact on cardiac events in primary and secondary prevention of coronary heart disease. Given the efficacy of the statins, the need for strict dietary modification in patients on statin therapy has been questioned. This study was performed to assess 1) the added benefit on serum lipid levels of a strict low-fat dietary regimen in patients with hypercholesterolaemia already treated with simvastatin; 2) the efficacy of simvastatin on the lipid profile of our sample Asian population; and 3) the tolerability and side-effect profile of simvastatin. This study was a prospective evaluation of 60 patients with hypercholesterolaemia treated with simvastatin who were subjected to either a normal diet or a dietitian guided low-fat diet. Assessment of the effects on serum lipid levels, side-effects, biochemical and haematological markers were performed. After 24 weeks of treatment, a strict dietitian guided low-fat diet conferred no additional benefit over and above what was achieved by simvastatin alone. Furthermore, a higher dose of simvastatin was needed in the dietitian guided diet group to achieve the target LDL-cholesterol level. Simvastatin resulted in a significant positive alteration of lipid profiles in all patients. The drug was well tolerated, with no significant change in either haematological or biochemical indices. Simvastatin is a highly effective cholesterol-lowering drug with a beneficial effect on the entire lipid spectrum in a cross-section of Asian patients, and is well tolerated. A dietitian guided dietary approach confers no additional advantage once statin therapy has been initiated.     

Subacute immune response to primary EBV infection leading to post-transplant lymphoproliferative disease in a renal transplant patient

A 23-year-old man sero-negative for Epstein-Barr virus (EBV) developed recurrent sore throats 3 and 6 months after a renal transplant from an EBV sero-positive donor. Tonsillar biopsy at 9 months post-transplant showed post-transplant lymphoproliferative disease (PTLD) caused by EBV. Following reduction of immunosuppressive treatment, he developed further signs and symptoms, and serological evidence of infectious mononucleosis followed by resolution of lymphadenopathy. This case emphasizes the difficulty in interpreting EBV serology in immunosuppressed patients and the importance of pre-transplant EBV serology.