RESUMO
The Na+-activated Na+ channel (Nax) and salt-inducible kinase (SIK) are stimulated by increases in local Na+ concentration, affecting (Na+ + K+)-ATPase activity. To test the hypothesis that the triad Nax/SIK/(Na+ + K+)-ATPase contributes to kidney injury and salt-sensitive hypertension (HTN), uninephrectomized male Wistar rats (200 g; n = 20) were randomly divided into 4 groups based on a salt diet (normal salt diet; NSD-0.5% NaCl-or high-salt diet; HSD-4% NaCl) and subcutaneous administration of saline (0.9% NaCl) or deoxycorticosterone acetate (DOCA, 8 mg/kg), as follows: Control (CTRL), CTRL-Salt, DOCA, and DOCA-Salt, respectively. After 28 days, the following were measured: kidney function, blood pressure, (Na+ + K+)-ATPase and SIK1 kidney activities, and Nax and SIK1 renal expression levels. SIK isoforms in kidneys of CTRL rats were present in the glomerulus and tubular epithelia; they were not altered by HSD and/or HTN. CTRL-Salt rats remained normotensive but presented slight kidney function decay. HSD rats displayed augmentation of the Nax/SIK/(Na+ + K+)-ATPase pathway. HTN, kidney injury, and kidney function decay were present in all DOCA rats; these were aggravated by HSD. DOCA rats presented unaltered (Na+ + K+)-ATPase activity, diminished total SIK activity, and augmented SIK1 and Nax content in the kidney cortex. DOCA-Salt rats expressed SIK1 activity and downregulation in (Na+ + K+)-ATPase activity in the kidney cortex despite augmented Nax content. The data of this study indicate that the (Na+ + K+)-ATPase activity response to SIK is attenuated in rats under HSD, independent of HTN, as a mechanism contributing to kidney injury and salt-sensitive HTN.
Assuntos
Acetato de Desoxicorticosterona , Hipertensão , Ratos , Masculino , Animais , Cloreto de Sódio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Ratos Wistar , Hipertensão/metabolismo , Sódio/metabolismo , Cloreto de Sódio na Dieta/efeitos adversos , Cloreto de Sódio na Dieta/metabolismo , Pressão Sanguínea , Rim/metabolismo , Íons/metabolismo , Proteínas Serina-Treonina Quinases/metabolismoRESUMO
Renal ischemia-reperfusion injury (IRI) is a major cause of acute renal failure. Doxycycline (Dc) belongs to the tetracycline-class of antibiotics with demonstrated beneficial molecular effects in the brain and heart, mainly through matrix metalloproteinases inhibition (MMP). However, Dc protection of renal function has not been demonstrated. We determined whether low doses of Dc would prevent decreases in glomerular filtration rate (GFR) and maintain tubular Na+ handling in Wistar rats subjected to kidney I/R. Male Wistar rats underwent bilateral kidney ischemia for 30min followed by 24h reperfusion (I/R). Doxycycline (1, 3, and 10mg/kg, i.p.) was administered 2h before surgery. Untreated I/R rats showed a 250% increase in urine volume and proteinuria, a 60% reduction in GFR, accumulation of urea-nitrogen in the blood, and a 60% decrease in the fractional Na+ excretion due to unbalanced Na+ transporter activity. Treatment with Dc 3mg/kg maintained control levels of urine volume, proteinuria, GFR, blood urea-nitrogen, fractional Na+ excretion, and equilibrated Na+ transporter activities. The Dc protection effects on renal function were associated with kidney structure preservation and prevention of TGFß and fibronectin deposition. In vitro, total MMP activity was augmented in I/R and inhibited by 25 and 50µM Dc. In vivo, I/R augmented MMP-2 and -9 protein content without changing their activities. Doxycycline treatment downregulated total MMP activity and MMP-2 and -9 protein content. Our results suggest that treatment with low dose Dc protects from IRI, thereby preserving kidney function.
Assuntos
Injúria Renal Aguda/patologia , Citoproteção/efeitos dos fármacos , Doxiciclina/farmacologia , Rim/efeitos dos fármacos , Traumatismo por Reperfusão/patologia , Injúria Renal Aguda/fisiopatologia , Animais , Relação Dose-Resposta a Droga , Taxa de Filtração Glomerular/efeitos dos fármacos , Rim/irrigação sanguínea , Rim/patologia , Rim/fisiologia , Masculino , Ratos , Ratos Wistar , Traumatismo por Reperfusão/fisiopatologiaRESUMO
BACKGROUND: We investigated whether a chronic low-protein multideficient diet (BRD) from weaning turns on cardiovascular adaptive responses that could culminate in hypertension and heart failure. METHODS AND RESULTS: Systolic pressure (SP) and heart rate (HR) were determined in CTRL (normal diet) and BRD rats. Plasma albumin, plasma urea and urinary urea excretion decreased in BRD rats. In this group, echocardiography and the Langendorff technique showed: (i) increased HR and hypertension; (ii) decreased LVDP, dP/dtmax, dP/dtmin, cardiac output, ejection fraction, stroke volume and left ventricular diameter. BRD rats were less sensitive to isoproterenol (ISO) in LVDP and dP/dtmax, with unchanged dP/dtmin; Pressure-volume relationships indicated left-oriented shifts in LVDP, SP and DP, and decreased capacitance compared to CTRL. BRD rats had higher cardiac and lung indexes, accompanied by muscle atrophy and recent ventricular-infarcted areas, higher ventricular ß1-AR content, and decreased ß2-AR and α1-AR. Propranolol treatment gave similar ISO responses in both groups, disappearance of the infarcted regions and, except for ß2-AR, recovery of normal receptor expression. BRD rats had intense stimulation of plasma membrane Ca2+-ATPase (PMCA) activity, with increased Ca2+ affinity and inhibition of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA). Ventricular phospholamban increased and Na+/Ca2+ exchanger decreased. PMCA activity correlated with an increase in its PKC-mediated phosphorylation, overlying a decrease in PKA-catalyzed phosphorylation. Propranolol normalized PKC and PKA activities with recovery of PMCA but not SERCA. CONCLUSION: BRD triggers sympathetic exacerbation and dysfunction in Ca2+ handling, accompanied by early onset of hypertension and left ventricle congestive heart failure.
Assuntos
Dieta com Restrição de Proteínas/efeitos adversos , Insuficiência Cardíaca/metabolismo , Hipertensão/metabolismo , Desnutrição/metabolismo , Deficiência de Proteína/metabolismo , Animais , Sinalização do Cálcio/fisiologia , Doença Crônica , Dieta com Restrição de Proteínas/tendências , Insuficiência Cardíaca/etiologia , Insuficiência Cardíaca/patologia , Hipertensão/etiologia , Hipertensão/patologia , Masculino , Desnutrição/patologia , Deficiência de Proteína/patologia , Proteínas Quinases/metabolismo , Ratos , Ratos Wistar , Fatores de Tempo , Ureia/metabolismoRESUMO
Tissue damage by ischemia/reperfusion (I/R) results from a temporary cessation of blood flow followed by the restoration of circulation. The injury depresses mitochondrial respiration, increases the production of reactive oxygen species (ROS), decreases the mitochondrial transmembrane potential, and stimulates invasion by inflammatory cells. The primary objective of this work was to address the potential use of bone marrow stem cells (BMSCs) to preserve and restore mitochondrial function in the kidney after I/R. Mitochondria from renal proximal tubule cells were isolated by differential centrifugation from rat kidneys subjected to I/R (clamping of renal arteries followed by release of circulation after 30 min), without or with subcapsular administration of BMSCs. Respiration starting from mitochondrial complex II was strongly affected following I/R. However, when BMSCs were injected before ischemia or together with reperfusion, normal electron fluxes, electrochemical gradient for protons, and ATP synthesis were almost completely preserved, and mitochondrial ROS formation occurred at a low rate. In homogenates from cultured renal cells transiently treated with antimycin A, the coculture with BMSCs induced a remarkable increase in protein S-nitrosylation that was similar to that found in mitochondria isolated from I/R rats, evidence that BMSCs protected against both superoxide anion and peroxynitrite. Labeled BMSCs migrated to damaged tubules, suggesting that the injury functions as a signal to attract and host the injected BMSCs. Structural correlates of BMSC injection in kidney tissue included stimulus of tubule cell proliferation, inhibition of apoptosis, and decreased inflammatory response. Histopathological analysis demonstrated a score of complete preservation of tubular structures by BMSCs, associated with normal plasma creatinine and urinary osmolality. These key findings shed light on the mechanisms that explain, at the mitochondrial level, how stem cells prevent damage by I/R. The action of BMSCs on mitochondrial functions raises the possibility that autologous BMSCs may help prevent I/R injuries associated with transplantation and acute renal diseases.