HEAT SHOCK PROTEIN 25 (HSP 25) AND HSP 70 EXPRESSION IN LOW PROTEIN FED-RATS

PATRICIA G. VALLES; LILIANA CARRIZO; DARÍO CUELLO-CARRIÓN; WALTER MANUCHA; DANIEL CIOCCA

Sidney - Australia

Congreso; Congreso Internacional de Nefrología Pediátrica; 2004

Asociación Internacional de Nefrología Pediátrica

Heat shock protein (HSP) synthesis is increased in response to cell injury from a variety of renal insults. Previous studies have shown that Angiotensin II can induce expression of these HSPs in renal cells. Malnutrition, a stressful condition to the kidney, includes enhanced expression of the genes that encode for various components of the Renin Angiotensin System. Objective of the study: We investigated the impact of LP consumption on HSP25 and HSP70 expression in the kidney. Methods; The study was performed in three groups of rats: 1) LP fed-rats (protein 8% for fifteen days), 2) control rats (CP) protein 24%, and 3) protein recovery group (RP) with re-administration of 24% protcin (nephrectomy was carried out at days 3, 7 and 15 of the recovery period). Angiotensin II AT1 expression by RT-PCR was performed. HSP25 and HSP70 protein expression were evaluated by Westem Blot and immunohistochemistry. Results: Densitomettie analysis of the AT1 Angiotensin II receptor mRNA corrected for B-actin expression (relative densitometric units) showed a significant two fold increase on LP cortex compared to CP: 2.27±0.2 vs 1.13±0.1 (p<0.01). Lower expression was shown in LP medula compared to CP: 1.47±0.1 vs 1.0±0.07 (p<0.05). Readministration of 24% protein (15 days) in the diet showed increased AT1 receptor expression in kidney cortex related to control: 2.51±0.3 vs. 1.13±0.1 (p<0.01), slight AT1 receptor increase expression was found in the LP kidney medulla: 1.87±0.01 vs 1±0.07, p<0.05. In LP, immunohistochemistry revealed that HSP25 expression increased in intensity in the endothelium and medial smooth muscle of the renal arteries in the cortex. In medula the immunoreaction for HSP2S appeared with an increasing intensity gradient when the MCDs were closer to the papilla. HSP2S immunostaining was observed in IMCDs with a tendency to be higher in the membranes. HSP70 was clearly observed in the cytoplasm and nuclei of CCDs and PCTs (with high expression at the brush borders of PCTs) in LP related to control. In LP rat medula, HSP70 appeared in the cytoplasm of OMCD cells. The amount of HSP70 protein from LP relative to that of controls were near two-fold higher in cortex (1.75±0.2 n:4 p<0.05, in medulla 2.37±0.2, n 4 p<0.01. Re-administration of 24% protein showed intense immunoreaction for HSP2S and HSP70 in the tubular lumen in the form of cylinders in the OMCDs and IMCDs. The observation of cylinders strongly reactive for HSP70 appeared at 3 days but higher numbers were showed at 7 and 15 days. At 3 days of recuperation, there were few cylinders but the duets showed the strongest HSP70 immunoreaction. In addition, HSP70 protein levels in renal medulla were 2.5 fold higher than control. p<0.01 at the 3 day of recovery 1.6 fold and 1.5 fold higher than control, each p<0.05 each, seven and fifteen days after recovery respectively. Conclusions: These results support the concept that HSP25 and mainly HSP70 are involved in the adaptative response of the kidney to injury caused by low protein feeding. Moreover the increased expression of AT1 receptor suggests Angiotensin II modulation.