Effects of chronic heat stress on the expressions of heat shock proteins 60, 70, 90, A2, and HSC70 in the rabbit testis

Abstract

Few studies have focused on the expression of heat shock proteins (HSPs) after chronic heat stress. The objective of this study was to investigate the effect of chronic high temperature-humidity index treatment on the expressions of HSP60, HSP70, HSP90, HSPA2 and HSC70, in the Rex rabbit testis and the expressions of these proteins after recovery from the chronic heat shock. Thirty mature male rabbits of the same age were randomly divided into three groups: control, heat stress, and recovery. The western blot results showed that the expressional levels of HSP60, HSP90, and HSC70 increased significantly and HSPA2 was elevated slightly after a 9-week heat treatment. HSP70 was absent in the control testis and had a high level of expression after heat stress. All of these proteins partially reverted back to normal levels after a 9-week recovery. The immunohistochemical results indicated that the expression patterns of HSP60, HSP90, HSPA2, and HSC70 did not change.

Fig. 1

The temperature cycle during a single day of heat stress. HS rabbits were subjected to a heat regimen that imitates the summer climate of Beijing. From 7:00 to 11:00 hours, the temperature was gradually increased from 26°C to 36°C. The temperature was maintained at 36°C for 4 h and then gradually decreased to 26°C between 15:00 and 19:00 hours. Between 19:00 and 7:00 hours, the temperature was maintained at 26°C

Fig. 2

Expression of HSPs after heat stress by western blot. a HSP60, HSC70, HSP70, HSPA2, and HSP90 were detected in the testes of control (lane 1), heat stress (lane 2), and recovery (lane 3) rabbits. β-Actin was used as a reference. Statistical analysis the expression levels of HSP60 (b), HSC70 (c), HSP70 (d), HSPA2 (e), and HSP90 (f) in CON, HS, and RE rabbits. Band intensity was measured using Gel-Pro analyzer software and normalized against that of β-actin. Data were presented as the mean ± SD and analyzed using general linear model. **P < 0.001, *P < 0.05

Fig. 3

Localization of HSP60, HSC70, HSPA2, and HSP90 proteins in the rabbit testes of control rabbits (CON), 9-week heat stress treated rabbits (HS), and recovery rabbits (RE). a HSP60 of control, b HSP60 of heat stress, c HSP60 of recovery, d HSC70 of control, e HSC70 of heat stress, f HSC70 of recovery, g HSPA2 of control, h HSPA2 of heat stress, i HSPA2 of recovery, j HSP90 of control, k HSP90 of heat stress, and l HSP90 of recovery. HSP60, HSC70, HSPA2. Positive staining is shown as brown. Spg spermatogonium, Spc spermatocyte, R round spermatids, S Sertoli cell, E elongated spermatid. Bar 20 μm

Fig. 4

Localization of HSP70 protein in the rabbit testes of nonstressed rabbit (a), 9-week heat stress-treated rabbit (b), and recovery rabbit (c). Positive staining is shown as brown. Spg spermatogonium, Spc spermatocyte, R round spermatid, S Sertoli cell. Bar 20 μm