Sodium nitrite protects against kidney injury induced by brain death and improves post-transplant function.

Renal injury induced by brain death is characterized by ischemia and inflammation, and limiting it is a therapeutic goal that could improve outcomes in kidney transplantation. Brain death resulted in decreased circulating nitrite levels and increased infiltrating inflammatory cell infiltration into the kidney. Since nitrite stimulates nitric oxide signaling in ischemic tissues, we tested whether nitrite therapy was beneficial in a rat model of brain death followed by kidney transplantation. Nitrite, administered over 2 h of brain death, blunted the increased inflammation without affecting brain death-induced alterations in hemodynamics. Kidneys were transplanted after 2 h of brain death and renal function followed over 7 days. Allografts collected from nitrite-treated brain-dead rats showed significant improvement in function over the first 2 to 4 days after transplantation compared with untreated brain-dead animals. Gene microarray analysis after 2 h of brain death without or with nitrite therapy showed that the latter significantly altered the expression of about 400 genes. Ingenuity Pathway Analysis indicated that multiple signaling pathways were affected by nitrite, including those related to hypoxia, transcription, and genes related to humoral immune responses. Thus, nitrite therapy attenuates brain death-induced renal injury by regulating responses to ischemia and inflammation, ultimately leading to better post-transplant kidney function.

Effects of venous needle turbulence during ex vivo hemodialysis on endothelial morphology and nitric oxide formation.

Arteriovenous grafts used for hemodialysis frequently develop intimal hyperplasia (IH), which ultimately leads to graft failure. Although the turbulent jet from the dialysis needle may contribute to vessel wall injury, its role in the pathogenesis of IH is relatively unexplored. In the current study, using bovine aortic endothelial cells (BAEC) cultured on the inner surface of a compliant tube, we evaluated the effects of simulated hemodialysis conditions on morphology and nitric oxide (NO) production. The flows via the graft and needle were 500 ml/min (Reynolds number=819) and 100ml/min (Reynolds number=954), respectively. In the presence of the needle jet for 6h, 19.3% (+/-1.53%) of BAEC were sheared off, whereas no loss of BAEC was observed in the presence of graft flow alone (P<0.05). In the presence of graft flow alone, assessment of cell orientation by the Saltykov method revealed that BAEC were oriented along the flow direction. This alignment, however, was lost in the presence of needle flow. Finally, NO production was also significantly decreased in the presence of the needle flow compared to the presence of graft flow alone (16+/-3.1 vs 34.7+/-1.9 nmol/10(6)cells/h, P<0.05). NO is a key player in vascular homeostasis mechanisms modulating vasomotor tone, inhibiting inflammation and smooth muscle cell proliferation. Thus, the loss of NO signaling and the loss of endothelial integrity caused by needle jet turbulence may contribute to the cascade of events leading to IH formation during hemodialysis.

Fibroblast growth factor receptor-1 signaling induces osteopontin expression and vascular smooth muscle cell-dependent adventitial fibroblast migration in vitro.

BACKGROUND: Increased expression of osteopontin (OPN), fibroblast growth factors (FGFs), and their type-1 receptor (FGFR-1) is associated with neointima formation and atherosclerosis. This study tested the hypothesis that ligand activation of FGFR-1 stimulates OPN expression in rat aortic smooth muscle cells (RASMCs), explored the signaling pathway involved, and assessed the functional consequences of activating this pathway on adventitial fibroblast (AF) migration in vitro. METHODS AND RESULTS: Exogenous FGF-1 stimulated expression of OPN mRNA and protein in RASMCs in vitro in a dose- and time-dependent manner. OPN mRNA induction by FGF-1 was completely inhibited by either actinomycin D or cycloheximide, selective inhibitors of RNA polymerase and protein synthesis, respectively. OPN mRNA induction by FGF-1 was attenuated by PD 166866, a highly selective and potent FGFR-1 tyrosine kinase inhibitor. Addition of either PP2 or PD98059, specific inhibitors of Src and mitogen-activated extracellular signal-regulated kinase (MEK)/mitogen-activated protein (MAP) kinases, respectively, attenuated FGF-1-stimulated OPN mRNA expression. FGF-1 treatment of RASMCs enhanced RASMC-conditioned medium-stimulated AF migration; this effect was inhibited by pretreatment of RASMCs with either PD166866 or PP2. Immunodepletion of OPN from RASMC-conditioned medium inhibited both basal and FGF-1-stimulated AF migration. CONCLUSIONS: This in vitro study provided a first indication that ligand-activated FGFR-1 plays a significant role in upregulation of OPN expression at the transcriptional level via signaling to Src/MEK/MAP kinases in RASMCs and that this pathway is functionally significant in mediating AF migration via stimulation of OPN expression.