Expression Dynamics of Heat Shock Proteins (HSP) in Livestock under Thermal Stress

Abstract

Increased ambient temperature increases heat gain by animal which results in heat stress and reduced performance, leading to decreased efficiency of livestock farming. In addition to adaptive biochemical, endocrine and physiological responses, the molecular events that underlie thermotolerance involve the coordinated synthesis of series of heat stress responsive genes, which are responsible for amelioration of deleterious effects of heat stress. Heat Shock Proteins (LISP) are the key players in the adaptive responses to the stress. Intracellular HSP70 confers cytoprotection against thermal and oxidative stress induced cellular damage. Heat Shock Factor (fISF) are the regulatory proteins that is activated by heat stress and control transcription of LISP by binding to Heat Shock Elements (HSE) in HSP genes. Heat shock causes profound modulation in cell signaling pathways that lead to transcription of Nitric oxide synthases (NOS), Toll like receptors and Interleukins. Studies on heat stress in livestock and model animals indicate that TER 2/4 and IL 2/6 possibly play a vital role via activation of the JAK-STAT pathway, Crosstalk between HSP90, iNOS and eNOS play an important role in mitigating thermal insults and confer thermo tolerance during long term heat stress exposure in livestock. Recent study indicates important roles of Vitamin C, Vitamin E plus Selenium and Betaine as an antioxidant in maintenance of cellular homeostasis. Positive correlation has been found between melatonin and IISP, which explains its importance in heat stress adaptation. These mechanisms possibly work in an orchestrated manner to minimize the devastating effect of heat stress and play pivotal role in the thermotolerance by blocking heat stress -induced cellular death, which helps livestock in acclimation to heat stress.