Heat shock protein 25 (Hsp25) and Hsp70 expression in low protein fed-rats

VALLÉS P.; CARRIZO L.; CUELLO CARRIÓN F. D.; MANUCHA W.; CIOCCA D. R.

Adelaida, Australia

Congreso; The 13th Congress of the International Pediatric Nephrology Association.; 2004

International Pediatric Nephrology Association

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 stressfull 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% protein (nephrectomy was carried out at days 3, 7 and 15 of the recovery period). Angiotensin Il AT1 expression by RT-PCR was performed. Hsp25 and Hsp70 protein expression were evaluated by Westem Blot and immunohistochemistry. Results: Densitometric analysis of the AT1Angiotensin II receptor mRNA corrected for beta-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 medulla compared to CP: 1.47 ± 0.1 vs 1.09 ± 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 medula: 1.87 ± 0.10 vs 1.09 ± 0.07 (P < 0.05). ln LP immunohistochemistry revealed that Hsp25 expression increased in intensity in the endothelium and medial smooth muscle of the renal arteries in the cortex. ln medulla the immunoreaction for Hsp25 appeared with an increasing intensity gradient when the MCDs were closer to the papilla. Hsp25 immunostaining was observed in lMCDs with a tendency to be higher in the membranes. Hsp70 was clearly observed in the cytoplasm and nuclei of CDDs and PCTs (with high expression al the brush borders of PCTs) in LP related to control. In LP rat medulla, 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 Hsp25 and Hsp70 in the tubular lumen in the form of cylinders in the OMCOs and IMCDs. The observation of cylinders strongly reactive for Hsp70 appeared at 3 days but higher numbers were showed alt 7 and 15 days. At 3 days of recuperatíon, there were few cylinders but the ducts 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 3rd 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 adaptalive response of the kidney to injury caused by low protein feeding. Moreover, the increased expression of AT1 receptor suggests Angiotensin II modulation.