Exploring the interplay between inflammation and male fertility

Male fertility results from a complex interplay of physiological, environmental, and genetic factors. It is conditioned by the properly developed anatomy of the reproductive system, hormonal regulation balance, and the interplay between different cell populations that sustain an appropriate and functional environment in the testes. Unfortunately, the mechanisms sustaining male fertility are not flawless and their perturbation can lead to infertility. Inflammation is one of the factors that contribute to male infertility. In the testes, it can be brought on by varicocele, obesity, gonadal infections, leukocytospermia, physical obstructions or traumas, and consumption of toxic substances. As a result of prolonged or untreated inflammation, the testicular resident cells that sustain spermatogenesis can suffer DNA damage, lipid and protein oxidation, and mitochondrial dysfunction consequently leading to loss of function in affected Sertoli cells (SCs) and Leydig cells (LCs), and the formation of morphologically abnormal dysfunctional sperm cells that lay in the basis of male infertility and subfertility. This is due mainly to the production and secretion of pro-inflammatory mediators, including cytokines, chemokines, and reactive oxygen species (ROS) by local immune cells (macrophages, lymphocytes T, mast cells) and tissue-specific cells [SCs, LCs, peritubular myoid cells (PMCs) and germ cells (GCs)]. Depending on the location, duration, and intensity of inflammation, these mediators can exert their toxic effect on different elements of the testes. In this review, we discuss the most prevalent inflammatory factors that negatively affect male fertility and describe the different ways inflammation can impair male reproductive function.