TNF-α-mediated cardiorenal injury after rhabdomyolysis in rats.

The TNF-α serum level increases after rhabdomyolysis and is involved in the subsequent cardiorenal injury. In the present study, we investigated the TNF-α-dependent cell signaling pathways implicated in cellular injury in these organs. Rhabdomyolysis was induced by intramuscular glycerol injection in rats. Renal function, cardiac and renal pathology, and activation of caspases were evaluated during the first 24 h after glycerol injection. TNF-α blockade with infliximab reduced tubular necrosis and cardiorenal apoptosis. Cellular Fas-associated protein with death domain-like IL-1ß-converting enzyme inhibitory protein (cFLIP), an inhibitor of caspase-8, was overexpressed in the kidney but not in the heart. The inhibitory effect of cFLIP blunted caspase-8 activation in the kidney. In this condition, the cellular response to the TNF-α stimulus was driven to receptor-interacting protein-1 (RIP1)-mediated necroptosis. Treatment with RIP1 inhibitor (necrostatin-1) isolated or in combination with infliximab showed a similar reduction in tubular necrosis, underscoring the importance of TNF-α-mediated tubular necroptosis in this model. TNF-α played a positive regulatory role in the transcription of proapoptotic Bax and p53-upregulated modulator of apoptosis (PUMA) proteins. Infliximab treatment reduced caspase-9-mediated apoptosis in both organs. Treatment with a caspase-8 inhibitor showed that caspase-8 participated in the process of apoptosis only in the heart, upstream of caspase-9 activation. TNF-α-mediated necroptosis is the predominant form of tubular injury observed in the glycerol model. TNF-α up regulates Bax and PUMA proapoptotic proteins, resulting in activation of the intrinsic pathway of apoptosis in the kidney and heart.

p53-Mediated oxidative stress and tubular injury in rats with glycerol-induced acute kidney injury.

BACKGROUND/AIMS: p53 is a transcriptional factor that responds to severe cell damage promoting the transcription of proapoptotic and prooxidant genes. In this study, we evaluated the role of p53 activation in glycerol-induced acute kidney injury (Gly-AKI). METHODS: Rats were treated with p53 inhibitor (pifithrin-α) in the moment we injected glycerol. Renal function, renal histology (HE), TUNEL labeling, cleaved caspase-3 staining, renal p53, Bax, PUMA, Bcl-2, p21 and survivin expressions, renal lipid and DNA oxidative markers, and the expression of antioxidant enzymes (Mn-SOD, HO-1, and NAD(P)H:quinone-oxidoreductase-1) were evaluated. RESULTS: Gly-AKI rats showed an increased renal expression of phosphorylated-p53. The p53 inhibitor attenuated renal impairment and significantly reduced tubular injury. The expression of the oxidative markers was significantly reduced in treated rats. Proapoptotic and prooxidant proteins Bax and PUMA were overexpressed in Gly-AKI rats and reduced in treated rats. On the contrary, antiapoptotic Bcl-2, p21, and survivin showed a tendency to increase in treated rats. The antioxidant enzymes' expression remained elevated or increased in treated rats. CONCLUSION: On the whole, p53 inhibition was protective in the short term. The oxidative stress subsided and the transcription tipped toward prosurvival genes; consequently tubular injury was attenuated in treated rats.

Silymarin exacerbates p53-mediated tubular apoptosis in glycerol-induced acute kidney injury in rats.

BACKGROUND/AIMS: Silymarin is an herbal extract with antioxidant properties that can reduce oxidative stress-mediated injuries in murine models of liver, heart, and kidney diseases. Silymarin can also increase p53-mediated cellular apoptosis in vitro. We tested the effect of silymarin administration before glycerol-induced acute kidney injury (Gly-AKI) in rats. METHODS: Renal function, tubular injury, oxidative stress, leukocytes infiltration, and renal expression of apoptosis regulating proteins (p53, p-p53, Bax, Bcl-2, survivin, and cleaved caspase-3) were evaluated 6 or 24 h after glycerol. RESULTS: Silymarin exacerbated the renal impairment and tubular apoptosis but had no effect on tubular necrosis or renal leukocytes infiltration. Renal lipid and DNA peroxidation was increased after glycerol and silymarin did not reduce oxidative stress. Proteins p53, p-p53, and proapoptotic Bax were upregulated in Gly-AKI rats treated with silymarin, whereas anti-apoptotic Bcl-2 was reduced in this group. Cleaved caspase-3 was overexpressed in Gly-AKI rats, particularly when treated with silymarin. Survivin was less expressed in Gly-AKI than in controls, but this deficit was not aggravated by silymarin. CONCLUSION: The persistence of oxidative stress, inflammatory reaction, and tubular necrosis, as well as exacerbation of p53-mediated tubular apoptosis, led to a more severe renal impairment in Gly-AKI rats treated with silymarin.

Endogenous hepatocyte growth factor attenuates inflammatory response in glycerol-induced acute kidney injury.

BACKGROUND: Hepatocyte growth factor (HGF) is overexpressed after acute kidney injury (AKI). The aim of this study was to evaluate the role of endogenous HGF in the progression of the inflammatory response in glycerol-induced AKI (Gly-AKI) in rats. METHODS: Renal and systemic HGF expressions were evaluated during the development of Gly-AKI. Subsequently, the blockade of endogenous HGF was analyzed in rats treated with anti-HGF antibody concomitant to glycerol injection. Apoptosis, cell infiltration and chemokine and cytokine profiles were investigated. RESULTS: We detected an early peak of renal and plasma HGF protein expressions 3 h after glycerol injection. The pharmacological blockade of the endogenous HGF exacerbated the renal impairment, the tubular apoptosis, the renal expression of monocyte chemoattractant protein-1 and the macrophage, CD43+, CD4+ and CD8+ T lymphocytes renal infiltration. The analysis of mRNA expressions of Th1 (t-bet, TNF-alpha, IL-1beta) and Th2 (gata-3, IL-4, IL-10) cytokines showed a Th1-polarized response in Gly-AKI rats that was aggravated with the anti-HGF treatment. CONCLUSION: Endogenous HGF attenuates the renal inflammatory response, leukocyte infiltration and Th1 polarization after glycerol injection. The control of cellular immune response may partly explain the protective effect of endogenous HGF in the development of Gly-AKI.

Attenuation of glycerol-induced acute kidney injury by previous partial hepatectomy: role of hepatocyte growth factor/c-met axis in tubular protection.

BACKGROUND/AIMS: Previous partial hepatectomy (HPTX) can attenuate glycerol-induced acute kidney injury (Gly-AKI). The aim of this study was to explore the pathophysiological mechanisms and the role of hepatocyte growth factor (HGF) in kidney protection. METHODS: Rats were subjected to HPTX 24 h before glycerol administration. Renal function, acute tubular necrosis, apoptosis, leukocyte infiltration, and the expression of HGF, c-met, monocyte chemoattractant protein-1, interleukin-1beta, and heme oxygenase-1 were evaluated 24 h after glycerol injection. The regenerative response was analyzed from 6 to 72 h after glycerol injection (BrdU incorporation). In a separate series of experiments, Gly-AKI+HPTX rats were treated with anti-HGF antibody. RESULTS: Gly-AKI+HPTX rats showed an increased expression of renal HGF and c-met as well as an improved creatinine clearance and reduced acute tubular necrosis and apoptosis, cytokine expression, and leukocyte infiltration. The regenerative response was less intense 24 and 72 h after glycerol administration in this group. The anti-HGF treatment disclosed an important role of HGF in the reduction of tubular injury, particularly apoptosis. Overexpression of heme oxygenase-1 was observed in Gly-AKI+HPTX rats, but was not associated with HPTX-induced renal protection. CONCLUSION: We conclude that Gly-AKI+HPTX rats have a reduced susceptibility to renal injury instead of an increased regenerative response and that endogenous HGF overexpression is responsible for suppression of tubular apoptosis.

Effects of melatonin administration to rats with glycerol-induced acute renal failure.

Melatonin, the pineal hormone with antioxidative properties was administered to rats with glycerol-induced myoglobinuric acute renal failure (Gly-ARF). This model is characterized by acute tubular necrosis mediated by heme-iron oxidative stress. Rats received melatonin (20 mg/kg) concomitant and 3 h after glycerol injection. Gly-ARF rats showed at 24 h a 78% reduction in glomerular filtration rate, whereas this decrement was significantly reduced to 35% in the melatonin treated Gly-ARF rats. Tubular function evaluated by tubular reabsorption of sodium and lithium was also preserved in melatonin treated rats. The histologic analysis revealed extensive cortical tubular necrosis that was significantly reduced by melatonin treatment. The renal concentration of malondialdehyde (MDA) was increased 6 h after glycerol injection in Gly-ARF and this elevation was prevented when melatonin was administered. Renal concentration of reduced glutathione (GSH) was decreased at 6 h in Gly-ARF and melatonin did not reverse this decrease. It was concluded that melatonin administration attenuated the renal injury in the glycerol model of acute renal failure and reduced kidney oxidative stress through a GSH-independent mechanism.