Role of HSP70 in the regulation of the testicular apoptosis in a seasonal breeding teleost Prochilodus argenteus from the São Francisco river, Brazil

Abstract

This study investigated the relationship among heat shock protein 70 (HSP70), proliferating cell nuclear antigen (PCNA), and testicular apoptosis during a breeding cycle of Prochilodus argenteus, a neotropical migratory characiform fish of importance in commercial fishery from the São Francisco River basin. A total of 48 (12 fish/sampling) adult males were caught using casting and drifting nets in four samplings from June 2008 to March 2009. Immunohistochemistry, Western blotting, terminal transferase-mediated dUTP nick-end labeling (TUNEL), enzyme-linked immunosorbent assay (ELISA), and caspase-3 colorimetric assay were assessed in different phases of spermatogenesis. Labeling for HSP70 occurred in spermatogonia (SPG(A) 18.0±1.5 and SPGB 27.9±1.0 in 100 mm(2), respectively) and Sertoli cells in all sampling periods, with higher values in June (resting period) while spermatocytes were labeled in September (maturation period) and December (ripe period). For PCNA, immunoreaction was predominant in spermatogonia in June and September, while primary spermatocytes were labeled mainly in December (18.7±2.0). TUNEL-positive reaction occurred throughout the sampling periods, and labeling was detected in the nucleus of germ cells in all developmental phases, except spermatozoa. By ELISA, total HSP70 in testis increased significantly from June to December, and decreased in March (regression period), P<0.05. Caspase-3 activity decreased from June to December and increased in March. Taken together, our results suggest that HSP70 may protect the germ cells from caspase-3-dependent apoptosis during testicular activity and, reduction of HSP70 and increase of apoptosis contribute for testicular remodeling after the breeding season in wild populations of P. argenteus in the São Francisco River.