Contents lists available at ScienceDirect Journal of Thermal Biology journal homepage: www.elsevier.com/locate/jtherbio Expression analysis of Toll like receptors and interleukins in Tharparkar cattle during acclimation to heat stress exposure Jaya Bharati, S.S. Dangi, S.R. Mishra, V.S. Chouhan, V. Verma, O. Shankar, M.K. Bharti, A. Paul, Dilip K. Mahato, G. Rajesh, G. Singh, V.P. Maurya, S. Bag, Puneet Kumar, M. Sarkar ⁎ Physiology & Climatology Division, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh 243122, India ARTICLE INFO Keywords: Heat stress Interleukin PBMCs Toll like receptor Tharparkar cattle ABSTRACT Six male Tharparkar cattle of 2–3 years old were selected for the study. After 15 days acclimation at thermo neutral 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 (day 1, 5 and 12), after heat stress exposure (day 1–10, Short Term Heat Stress Acclimation - STHSA; day 15–23, Long Term Heat Stress Acclimation - LTHSA) and recovery period (day 7 and 12) and peripheral blood mononuclear cells (PBMCs) were isolated for RNA and protein extraction. Serum cortisol concentration was assessed by RIA. The mRNA and protein expression in PBMCs were determined by qPCR and western blot respectively. Samples at TNZ were taken as control. Serum cortisol concentration was increased (P < 0.05) during STHSA and gradually declined during LTHSA. Toll like receptor 2 (TLR 2) expression was up regulated (P < 0.05) during STHSA and declined to basal level during LTHSA and recovery phase. However, toll like receptor 4 (TLR 4) expression was up regulated (P < 0.05) during STHSA and LTHSA while declined in recovery phase. Interleukin 2 (IL2) and interleukin 6 (IL 6) were up regulated (P < 0.05) during STHSA and reduced to basal level during LTHSA. PBMCs culture study was conducted to study transcriptional abundance of TLR2/4 and IL2/6 at different temperature-time combinations. The present findings indicate that TLR 2/4 and IL 2/6 could possibly play a vital role in thermo tolerance in Tharparkar cattle during short term and long term heat stress exposure. 1. Introduction Steady increase in average temperature of earth due to global warming coupled with harsh environment of Indian subcontinent naturally exposes the livestock to thermal stress. Thermal stress is considered as the most important abiotic stress in tropical countries like India which affects the production as well as the economy (Wankar et al., 2014). Therefore, it is imperative to explore climate-resilient livestock breeds and their responses to thermal stress (Bharati et al., 2016). Thermo tolerance in most livestock is attributed by heat shock response and acclimatization to thermal stress (Kishore et al., 2014; Dangi et al., 2016). Tharparkar cattle, an important thermo tolerant breed of India also experiences the vagaries of heat stress beyond their thermo-neutral zone (TNZ) (Silanikove, 2000). Livestock are adapted to the local stress factors through differential regulation of stress hormones and gene expression pattern to recover from the harmful effects of heat stress. If the stress persists, the gene expression changes lead to an altered physiological state which is mostly controlled by the endocrine system (Collier et al., 2008). Adrenal glands are highly sensitive to changes in environmental heat load (Rasooli et al., 2004). Acute stressor activate the hypothalamus- pituitary-adrenal axis thereby increase cortisol concentration in serum of stressed farm animals (Dantzer and Mormede, 1983) which is regarded as a classical response to stress (Kannan et al., 2000). Heat stress acclimation is attributed by alteration in the expression pattern of several genes while persistent heat stress potentiates this effect to make the animal thermo tolerant to a particular agro climatic zone. Heat stress response is a complex phenomenon which involves physiological response (Hansen, 2004; Ganaie et al., 2013), alternation in gene expression profiling (Fujita et al., 1999; Dangi et al., 2012; Sharma et al., 2013) and immune response (Sonna et al., 2002; Dhabhar, 2003). Toll like receptors (TLRs) are mostly expressed on antigen presenting cells like monocytes, macrophages, dendritic cells and B lymphocytes (Zhou et al., 2005; Yan et al., 2007). TLRs recognize microbial markers like protein, carbohydrate, lipid, nucleic acids and/ or their combinations in a unique, non-self-reactive manner to onset a complex signalling cascade to trigger a wide variety of transcription factors and inflammatory cytokines (Takeda and Akira, 2003). The TLR http://dx.doi.org/10.1016/j.jtherbio.2017.02.002 Received 24 August 2016; Received in revised form 23 January 2017; Accepted 4 February 2017 ⁎ Corresponding author. E-mail address: msarkar24@gmail.com (M. Sarkar). Journal of Thermal Biology 65 (2017) 48–56 Available online 10 February 2017 0306-4565/ © 2017 Elsevier Ltd. All rights reserved. MARK