Expression dynamics of HSP90 and nitric oxide synthase (NOS) isoforms during heat stress acclimation in Tharparkar cattle.

Six male Tharparkar cattle of 2-3 years old were selected for the study. After 15-day acclimation at thermoneutral zone (TNZ) in psychrometric chamber, animals were exposed at 42 °C for 6 h up to 23 days followed by 12 days of recovery period. Blood samples were collected during control period at TNZ (days 1, 5, and 12), after heat stress exposure (day 1, immediate heat stress acclimation (IHSA); days 2 to 10, short-term heat stress acclimation (STHSA); days 15 to 23, long-term heat stress acclimation (LTHSA); days 7 and 12, recovery period), and peripheral blood mononuclear cells (PBMCs) were isolated for RNA and protein extraction. The messenger RNA (mRNA) and protein expression in PBMCs were determined by qPCR and western blot, respectively. Samples at TNZ were taken as control. The mRNA expression of HSP90, iNOS, and eNOS was significantly upregulated (P < 0.05) on day 1 (ISHA) as compared to control, remained consistent during STHSA, again increased during LTHSA, and finally reduced to basal level during recovery period. The protein expression of HSP90, iNOS, and eNOS were akin to their transcript pattern. PBMC culture study was conducted to study transcriptional abundance of HSP90, iNOS, and eNOS at different temperature-time combinations. The present findings indicate that HSP90, iNOS, and eNOS could possibly play an important role in mitigating thermal insults and confer thermotolerance during long-term heat stress exposure in Tharparkar cattle.