HSP70 family genes and HSP27 expression in response to heat and cold stress in vitro in peripheral blood mononuclear cells of goat (Capra hircus)

Abstract

The preferential expression of heat shock proteins confers transient thermal tolerance during heat or cold stress which is characterized by the heat or cold shock response and adaptations associated with acclimation. Goat occupies wide gamut of thermal niches and this variation relates to the extent of thermotolerance in this species. As the cellular response to thermal challenge is poorly understood in goat, the present study was undertaken in vitro to analyze the heat and cold challenge response in terms of expression of different heat shock protein family genes and HSP70 protein in the peripheral blood mononuclear cells (PBMCs) of goatlings. Total RNA and protein were isolated from the PBMCs after a thermal exposure at three different temperatures of 10°C (cold challenge), 38.5°C (control), and 42°C (heat challenge) for 3h. Quantitative real time polymerase chain reaction was performed to analyze the transcript variants of five HSP70 family genes (HSPA1A, HSPA1L, HSPA2, HSPA6 and HSPA8) and HSP27 in each thermal condition. The results clearly demonstrated that upon heat stress, the expression of all the genes studied except HSPA2 were significantly higher (p<0.0001) as compared to unstressed cells. No significant difference in the expression of HSPA1A, HSPA2, HSPA6 and HSPA8 was observed between cold stressed cells and their normal counterparts. HSP70 protein expression was also increased significantly in the heat challenged PBMCs. The major finding of this study was the increased levels of expression of HSP27 in both heat and cold stress conditions. Hence this study suggests HSP27 as useful indicator for assessing in vitro stress response, and provides the basis for validation of this gene as a thermal stress indicator in animals by further in vivo studies. Additionally, this study forms an essential step in understanding the cellular stress response in terms of HSP genes expression against heat and cold challenge in goat.