Low Doses of Cadmium Chloride and Methallothionein-1-Bound Cadmium Display Different Accumulation Kinetics and Induce Different Genes in Cells of the Human Nephron

Background/Aims: The present study was conducted to investigate the renal tubular handling of inorganic cadmium (Cd2+) by exposing primary human tubular cell cultures to physiologically relevant doses of cadmium chloride (CdCl2). Furthermore, the cellular accumulation of Cd2+ was compared to that of metallothionein-1-bound Cd (Cd7MT-1). Finally, this study aimed to investigate the effect of the accumulation of Cd (both Cd2+ and Cd7MT-1) in renal cells on the expression of genes relevant to nephrotoxic processes. Methods: Cd concentration was measured using atomic absorption spectrometry. mRNA expression was evaluated by quantitative real-time RT-PCR. Results: Cd2+ accumulated into human tubular cells in a concentration- and time-dependent way. Furthermore, cellular accumulation of Cd2+ was different from the cellular accumulation of Cd7MT-1, indicative for different uptake routes. Finally, mRNA expression of the genes encoding the anti-oxidative proteins metallothionein-1 (MT-1) and heme-oxygenase-1 (HO-1) as well as the pro-apoptotic Bcl-2-associated X protein (Bax) were upregulated by CdCl2 and not by Cd7MT1. Conclusion: In the presence of physiologically relevant Cd concentrations, tubular accumulation of the element in its inorganic form is different from that of Cd7MT-1. Furthermore, the tubular accumulation of inorganic Cd induces mRNA expression of genes of which the protein products may play a role in Cd-associated renal toxicity

Epoetin Delta Reduces Oxidative Stress in Primary Human Renal Tubular Cells

Erythropoietin (EPO) exerts (renal) tissue protective effects. Since it is unclear whether this is a direct effect of EPO on the kidney or not, we investigated whether EPO is able to protect human renal tubular epithelial cells (hTECs) from oxidative stress and if so which pathways are involved. EPO (epoetin delta) could protect hTECs against oxidative stress by a dose-dependent inhibition of reactive oxygen species formation. This protective effect is possibly related to the membranous expression of the EPO receptor (EPOR) since our data point to the membranous EPOR expression as a prerequisite for this protective effect. Oxidative stress reduction went along with the upregulation of renoprotective genes. Whilst three of these, heme oxygenase-1 (HO-1), aquaporin-1 (AQP-1), and B-cell CLL/lymphoma 2 (Bcl-2) have already been associated with EPO-induced renoprotection, this study for the first time suggests carboxypeptidase M (CPM), dipeptidyl peptidase IV (DPPIV), and cytoglobin (Cygb) to play a role in this process

T cells as mediators in renal ischemia/reperfusion injury

T cells as mediators in renal ischemia/reperfusion injury. Inflammation has been established to contribute substantially to the pathogenesis of ischemia/reperfusion (I/R) with a central role for particular cells, adhesion molecules, and cytokines. Until recently, most of the research trying to unravel the pathogenesis of I/R injury has been focused on the role of neutrophils. However, recent studies have brought evidence that T cells and macrophages are also important leukocyte mediators of renal and extrarenal (liver) I/R injury. In vivo depletion of CD4+ cells but not CD8+ cells in wild-type mice was protective in I/R of the kidney. A marked preservation of liver function was also found after I/R in T-cell deficient athymic mice. Blocking the b130/CD28 costimulatory pathway by CTLA-4 Ig (recombinant fusion protein) ameliorated renal dysfunction and decreased mononuclear cell infiltration in I/R of the kidney. b130-1 expression was found limited to the membrane of the endothelial cells of the ascending vasa recta, resulting in trapping of CD28-expressing CD4 T cells. This trapping of leukocytes results in the upstream congestion in the ascending arterial vasa recta, generating the since more than 150 years described medullary vascular congestion of the kidney soon after ischemic injury. It seems worthwhile to study a combination therapy using anti-inflammatory/anti-adhesion molecules in the early phase of I/R

DPP4 inhibition improves functional outcome after renal ischemia-reperfusion injury

Abstract: Glorie LF, Verhulst A, Matheeussen V, Baerts L, Magielse J, Hermans N, D'Haese PC, De Meester I, De Beuf A. DPP4 inhibition improves functional outcome after renal ischemia-reperfusion injury. Am J Physiol Renal Physiol 303: F681-F688, 2012. First published June 20, 2012; doi: 10.1152/ajprenal.00075.2012.-Dipeptidyl peptidase 4 (DPP4) is an exopeptidase which modulates the function of its substrates, among which are insulin-releasing incretins. DPP4 inhibitors are currently used to improve glucose tolerance in type 2 diabetes patients. Inhibition of DPP4 exhibits protective effects on ischemia-reperfusion injury (IRI) of the heart and lung. As DPP4 and its substrates are also expressed in the kidney, we studied the effect of the DPP4 inhibitor vildagliptin on the outcome of IRI-induced acute kidney injury in rats in a model of 30-min unilateral renal ischemia, followed by contralateral nephrectomy. Saline, 1, or 10 mg/kg vildagliptin (VG1/VG10) was administered intravenously 15 min before the surgery. Animals were euthanized after 2, 12, amd 48 h of reperfusion. DPP4 inhibition resulted in a significant dose-dependent decrease in serum creatinine (1.31 +/- 0.32 and 0.70 +/- 0.19 mg/dl for VG1 and VG10, respectively, vs. 1.91 +/- 0.28 mg/dl for controls at 12 h; P < 0.01). Tubular morphology (PAS-PCNA) revealed significantly reduced tubular necrosis at 12 h (62.1 +/- 18.0 and 77.5 +/- 22.0% in VG10 and saline, respectively). VG did not affect regeneration but decreased apoptosis, as shown by twofold decreased Bax/Bcl-2 mRNA expression and a threefold decrease in apoptotic bodies on terminal deoxynucleotidyl transferase dUTP nick-end labeling-stained sections. VG treatment significantly reduced serum malondialdehyde twofold in both VG1- and VG10-treated ischemic and sham-operated animals compared with controls and also resulted in a significant decrease in mRNA expression of the proinflammatory marker CXCL10 at 2 h of reperfusion. Through a mechanism yet to be fully understood, VG treatment results in a functional protection of the kidney against IRI. This protection was associated with antiapoptotic, immunological, and antioxidative changes