geranylgeranylacetone and Acute-Kidney-Injury

Recent reports suggest the presence of heat-shock protein (HSP)-reactive T cells with a regulatory phenotype in various inflammatory diseases. To test whether HSP exerts renoprotective effects through regulatory T cells (Tregs), ischemia/reperfusion injury was done with or without heat preconditioning in mice. Splenocytes from heat-preconditioned mice had Treg expansion and a reduced proliferative response upon mitogenic stimulus. T cells from heat-preconditioned mice failed to reconstitute postischemic injury when adoptively transferred to T cell-deficient nu/nu mice in contrast to those from control mice. Tregs were also increased in heat-preconditioned ischemic kidneys. Depleting Tregs before heat preconditioning abolished the renoprotective effect, while adoptive transfer of these cells back into Treg-depleted mice partially restored the beneficial effect of heat preconditioning. Inhibition of HSP70 by quercetin suppressed Treg expansion, as well as renoprotective effects. Transferring Tregs in quercetin-treated heat-preconditioned mice partially restored the beneficial effect of heat preconditioning. The specificity of immune cell HSP70 in renoprotection was confirmed by partial restoration of kidney injury when T cells from HSP70-deficient heat preconditioned mice were adoptively transferred to nu/nu mice. Thus, the renoprotective effect of HSP70 may be partially mediated by a direct immunomodulatory effect through Tregs. Better understanding of immunomodulatory mechanisms of various stress proteins might facilitate discovery of new preventive strategies in acute kidney injury.

Topics: Acute Kidney Injury; Animals; Cell Proliferation; Diterpenes; Forkhead Transcription Factors; Hot Temperature; HSP70 Heat-Shock Proteins; Interleukin-2 Receptor alpha Subunit; Male; Mice; Mice, Inbred C57BL; Mice, Nude; Phenotype; Reperfusion Injury; T-Lymphocytes, Regulatory

Heat shock protein 70 (Hsp70) is a potent antiapoptotic agent. Here, we tested whether it directly regulates renal cell survival and organ function in a model of transient renal ischemia using Hsp70 knockout, heterozygous, and wild-type mice. The kidney cortical Hsp70 content inversely correlated with tubular injury, apoptosis, and organ dysfunction after injury. In knockout mice, ischemia caused changes in the activity of Akt and glycogen synthase kinase 3-β (kinases that regulate the proapoptotic protein Bax), increased active Bax, and activated the proapoptotic protease caspase 3. As these changes were significantly reduced in the wild-type mice, we tested whether Hsp70 influences ischemia-induced apoptosis. An Hsp70 inducer, geranylgeranylacetone, increased Hsp70 expression in heterozygous and wild-type mice, and reduced both ischemic tubular injury and organ dysfunction. When administered after ischemia, this inducer also decreased tubular injury and organ failure in wild-type mice but did not protect the knockout mice. ATP depletion in vitro caused greater mitochondrial Bax accumulation and death in primary proximal tubule cells harvested from knockout compared with wild-type mice and altered serine phosphorylation of a Bax peptide at the Akt-specific target site. In contrast, lentiviral-mediated Hsp70 repletion decreased mitochondrial Bax accumulation and rescued Hsp70 knockout cells from death. Thus, increasing Hsp70 either before or after ischemic injury preserves renal function by attenuating acute kidney injury.

Topics: Acute Kidney Injury; Animals; Apoptosis; bcl-2-Associated X Protein; Diterpenes; Gene Expression; Gene Knockout Techniques; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; HSP70 Heat-Shock Proteins; Ischemia; Kidney; Mice; Mice, Inbred C57BL; Mice, Knockout; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Recombinant Proteins

Heat shock proteins (HSPs) are well known as cytoprotective proteins. Geranylgeranylacetone (GGA), an antiulcer agent, has recently been shown to induce Hsp70. This study was performed to investigate the renoprotective properties of GGA.. The effect of GGA on the induction of the major HSPs (Hsp90, Hsp70, Hsc70, Hsp60, and Hsp32) was studied in the rat kidney or rat primary cultures of tubular epithelial cells (R-TECs) by Western blot. Localization of Hsp70 was determined by immunohistochemistry. The renoprotective effects of GGA were studied using a rat model of ischemia/reperfusion (I/R) injury. GGA (400 mg/kg), GGA with quercetin pretreatment (100 mg/kg), or a vehicle was given to rats 24 hours and again 1 hour prior to the induction of I/R injury. Rats were sacrificed at 24 hours after reperfusion. Histologic analyses and terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) assay were performed. Blood urea nitrogen (BUN) and serum creatinine was also measured. The cytoprotective properties of GGA were also studied in vitro by treating R-TECs with GGA (10 mumol/L) or a vehicle, followed by incubation in culture medium with oxidative stress condition (0.5 mmol/L hydrogen peroxide) or ischemic condition (2 nmol/L NaCN and 20 mmol/L 2-deoxyglucose in the absence of medium glucose).. Oral administration of GGA induced Hsp70 expression in the kidney (which peaked at 24 hours) but did not induce Hsp90, Hsc70, Hsp60, or Hsp32. The induction of Hsp70 was blocked by quercetin. Immunohistochemistry showed that Hsp70 was localized mainly in the tubular epithelial cells. Preconditioning rats with GGA significantly decreased BUN and serum creatinine levels after I/R injury. Histologic examination revealed that GGA significantly attenuated tubular damage and macrophage infiltration. The number of TUNEL-positive cells also decreased significantly in the GGA group. Quercetin, an inhibitor of Hsp70 induction, eliminated these renoprotective effects of GGA. In in vitro study, GGA-induced Hsp70 in R-TECs, which peaked at 2 to 4 hours. Both oxidative stress and ischemic stimuli induced apoptosis in R-TECs. GGA significantly suppressed the number of apoptotic cells in both conditions.. The results support the hypothesis that GGA induces Hsp70, protects tubular epithelial cells from apoptosis, and thus ameliorates tubular damage by I/R injury. The present study suggests that GGA would be a useful tool in treating acute renal failure or preventing transplanted kidney damage in the clinical setting.

Topics: Acute Kidney Injury; Animals; Apoptosis; Diterpenes; HSP70 Heat-Shock Proteins; Hydrogen Peroxide; Ischemia; Kidney; Male; Quercetin; Rats; Rats, Sprague-Dawley