Xenobiotics are synthetic compounds foreign to the biological system. They often retain their qualities in the aquatic environment with the ability to cause oxidative stress in these organisms by activating the endogenous production of reactive oxygen species (ROS). Overloading of the estuaries with contaminants for a longer period has an impact on fish production. The grey mullet (Mugil cephalus) is capable of concentrating contaminants and is considered suitable for biomarker studies. Brain is an appropriate organ for the study of the effects of xenobiotics due to its morphological heterogeneity, metal accumulating capacity and susceptibility to histopathological damage by metals. Cells respond to stress in a variety of ways by activation of pathways that promote survival or apoptosis. Hence the present study aimed at understanding the effect of pollutants on fish brain by assessing stress markers (LHP, Trx) and signalling proteins (HIF1α, HSP70, CYP1A2 and ASK-1). The changes in the biomolecular composition was assessed using Fourier Transform Infrared Spectroscopy (FTIR). A significant increase in LHP and Trx reveals pollutant induced oxidative stress. An alteration in the functional groups of lipid and proteins were identified by FTIR. A variation in the expression of HIF1α and CYP1A2 infers xenobiotic induced stress. A significant elevation in the level of HSP 70 and insignificant increase in the level of ASK-1 depicts the prime role of HSP 70. Thus the present study concludes that upregulation of HSP70 plays a cytoprotective role during xenobiotic induced stress in fish brain.
Padmini Ekambaram* and Meenakshi Narayanan