Interleukin Gene Alterations and Growth Impairment in Teleost Fish under Heavy Metal Stress: A Review

Rapid industrialisation and the discharge of untreated effluents into freshwater bodies have made heavy metal pollution in aquatic ecosystems a serious environmental concern. Fish are crucial bioindicators for assessing environmental contamination and its biological effects, as they are highly sensitive aquatic species. Chromium (Cr), cadmium (Cd), lead (Pb), mercury (Hg), copper (Cu), arsenic (As), and other heavy metals have a substantial impact on fish physiology, immunology, growth, and survival. This review highlights the influence of heavy metal exposure on teleost fish immune regulation, with a focus on interleukin-mediated immune responses. Heavy metals cause oxidative stress, tissue damage, and inflammatory reactions, which alter the expression of TNF-α, IL-6, IL-1β, IL-2, IL-8, IL-10, IL-12, IL-17, and IL-18. These cytokines are essential for controlling inflammation, leukocyte recruitment, pathogen defense, tissue healing, and innate and adaptive immune responses. Exposure to toxic metals has been demonstrated to increase pro-inflammatory cytokines, including TNF-α, IL-1β, IL-6, IL-8, and IL-18, while dysregulating anti-inflammatory mediators like IL-10, leading to immunotoxicity and immunological imbalance. Heavy metals also trigger signalling pathways like NF-κB, which further increase the production of inflammatory genes and cause cellular damage. Teleost fish are useful models for researching environmental immunotoxicology because they have a highly conserved cytokine network similar to that of higher vertebrates. Fish health evaluation, biomarker development, and the ecological concerns associated with aquatic pollution can all benefit from an understanding of the molecular reactions of cytokines and interleukins to heavy metal stress. Effective environmental management techniques and sustainable aquaculture methods depend on this kind of knowledge.