# Functional and Molecular Characterization of Melamine-Induced Disruption of Human Spermatozoa via Oxidative Stress and Apoptotic Pathways: An In Vitro Study

## TL;DR

Melamine, an industrial chemical, harms human sperm function by causing oxidative stress and triggering cell death pathways, even at low concentrations.

## Contribution

This study is the first to demonstrate melamine's impact on human sperm capacitation and mitochondrial function in vitro.

## Key findings

- Melamine at 0.8 mM reduced sperm motility and disrupted capacitation processes like tyrosine phosphorylation and cholesterol efflux.
- Melamine caused mitochondrial dysfunction and increased reactive oxygen species, with COX4I1 downregulation observed.
- Exposure to melamine activated apoptotic pathways and increased sperm DNA fragmentation, especially during capacitation.

## Abstract

Melamine, a nitrogen-rich industrial chemical, has raised increasing concern as an emerging environmental contaminant with potential reproductive toxicity. While its nephrotoxic effects are well established, the direct impact of melamine on human sperm remains poorly defined. In this study, we investigated the in vitro effects of melamine on human sperm, under both capacitating and non-capacitating conditions. Functional analyses revealed that the exposure to 0.8 mM melamine, the highest non-cytotoxic concentration in vitro, significantly compromised sperm motility and disrupted key capacitation processes, including tyrosine phosphorylation patterns, cholesterol efflux, and the acrosome reaction. Molecular assessments demonstrated melamine-induced mitochondrial dysfunction, characterized by COX4I1 downregulation, reduced mitochondrial membrane potential, and altered reactive oxygen species production. In parallel, gene expression analyses revealed the activation of apoptotic pathways, with the upregulation of BAX and downregulation of BCL2, changes that were more pronounced during capacitation. Furthermore, melamine exposure significantly increased sperm DNA fragmentation and denaturation, indicating genotoxic stress. Collectively, these findings demonstrate that even low, non-cytotoxic concentrations of melamine compromise sperm function by disrupting capacitation, mitochondrial activity, and genomic integrity. This study identifies capacitation as a critical window of vulnerability and underscores the need to consider melamine as a potential environmental risk factor for male reproductive health.