A study on the molecular mechanism of acute heat stress response in testes of male Taiwan country chickens

• Main Authors: Shih-Han Wang, 王思涵
• Other Authors: 黃三元
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/38169325018958580693

博士 === 國立中興大學 === 動物科學系所 === 103 === Spermatogenesis is a complex process where spermatogonia differentiate into spermatozoa. In mammals, acute heat stress influences DNA integrity, transcription, translation, reactive oxygen species production and thus causes cell death, impairing spermatogenesis, and impairing development of blastocyts. Previous studies have shown that the mechanisms of acute heat stress on male reproduction in mammals; however, there are few studies has been carried out in avian species. Taiwan country chickens (TCCs) show better thermotolerance than commercial broilers. L2 strain TCCs and B strain TCCs have same genetic background, but egg production rate of L2 strain TCCs is greater than B strain TCCs duo to generations of egg selection in L2 strain. The purpose of this study was to explore the molecular response to acute heat stress in the testes of TCCs. The L2 strain (layer-type) and B strain (broiler-type) TCCs were used. Roosters were subjected to acute heat stress of 38℃ and 55% RH for 4 h. The heat-stressed roosters were then allowed to recover at 25℃ for 0, 2, and 6 h. The respiratory rate and body temperature were recorded during the treatment and recovery. The testis samples were collected at 0, 2, and 6 h of recovery for cell morphology, apoptosis, mRNA, and protein analysis. The body temperature and respiratory rate significantly increased in 1 h during heat stress and recovered at 2 h of recovery. In L2 strain TCCs, the numbers of abnormal spermatocytes, Sertoli cells, and Leydig cells (with hyperchromatic nuclei or multinucleated giant nuclei) increased at 2 h after acute heat stress. The TUNEL assay showed that a significant increase of apoptotic cells was observed at 2 h of recovery in the testes of heat-stressed L2 strain TCCs. The TUNEL-positive cells included spermatocytes, spermatids, and Sertoli cells. Microarray analysis showed that the mRNA expression of 309 genes changed in the testes of L2 strain TCCs after acute heat stress. The differentially expressed genes majorly participated in biological processes of metabolism, transport, responses to stimuli/stress, protein metabolism, and signal transduction/cell communication. There were 119 protein spots differentially expressed in the testes of heat-stressed L2 strain TCCs. These protein spots belonged to 92 distinct proteins and most of them involved in metabolism, protein folding, and proteolysis. In B strain TCCs, the numbers of abnormal spermatocytes and Sertoli cells were also increased after acute heat stress. The apoptotic cells in the testes of heat-stressed B strain TCCs, including spermatogonia, spermatocytes, spermatids, and Sertoli cells, increased at 2 h of recovery. Result of microarray analysis showed that the mRNA expression of 163 genes altered in the testes of B strain TCCs after heat stress. The differentially expressed genes were related to metabolism, transcription, cellular organization, response to stimulus, and signal transduction. Furthermore, there were 101 protein spots differentially expressed in the testes of B strain TCCs after acute heat stress. The differentially expressed protein spots represented 73 proteins and mostly involved in metabolism, protein metabolism, cell organization, response to stimulus, apoptosis, transport, homeostasis, and spermatogenesis. The results of this study showed that the apoptotic and abnormal spematogenic cells significantly increased in both layer-type and broiler-type TCCs at recovery time after acute heat stress. However, the abnormality and apoptosis were observed earlier in testes of broiler-type chickens than those in layer-type chickens. Beside, the levels of mRNA and protein showed different expression pattern between the 2 strains of TCCs because generations of egg production selection in L2 strain TCCs. In conclusion, the molecular mechanism of response to acute heat stress in the testes of layer-type TCCs may include the upregulation of HSP family and anti-apoptotic genes to attenuate the heat stress, and the downregulation of proteins related to translation to prevent unfolded protein synthesis. The genes and proteins associated with antioxidant reaction may also be induced to attenuate heat-induced oxidative damage. However, decreased expression of protein metabolism-related proteins, including CCT complex and proteasome subunits, may cause insufficiency of protein folding and degradation and thus trigger apoptosis. In broiler type TCCs, the mRNA and protein expression of HSP90α, HSC70, and HSPA5 were induced in the testes after acute heat stress. The expression of HSPs may thus induce the unfolded protein response to prevent accumulation of unfolded and misfolded protein. Nevertheless, the downregulation of anti-apoptotic genes and proteins may result in apoptosis in the testes of heat-stressed broiler-type TCCs.