# Rosemary essenitial oil counters MnO2 nanoparticle-induced fertility deficits in rats via antioxidant mechanisms and upregulation of StAR signalling

## TL;DR

Rosemary essential oil helps protect male rats from reproductive damage caused by manganese dioxide nanoparticles through antioxidant effects and improved hormone signaling.

## Contribution

This study demonstrates that rosemary essential oil can both prevent and treat reproductive toxicity caused by MnO2-NPs in rats.

## Key findings

- REO treatment reduced oxidative stress and restored antioxidant levels in MnO2-NP-exposed rats.
- REO improved sperm parameters and normalized hormone levels disrupted by MnO2-NPs.
- REO upregulated steroidogenic genes like StAR, HSD-3β, and CYP11A1 in testicular tissue.

## Abstract

Manganese, an essential nutrient for male reproductive health, exerts dose-dependent effects, with excessive exposure—particularly to manganese dioxide nanoparticles (MnO2-NPs) from environmental or industrial sources inducing gonadal damage via oxidative stress, hormonal disruption, and impaired steroidogenesis. This study evaluated rosemary essential oil (REO) against MnO2-NP-induced reproductive dysfunction in male rats. Seventy-two Sprague–Dawley rats (130 ± 10 g) were divided into six groups (n = 12): Group I (deionized water), Group II (saline), Group III (MnO2-NP, 100 mg/kg bw/day), Group IV (REO, 250 mg/kg/day), Protective Group V (REO pre-treatment + MnO2-NPs), and Therapeutic Group VI (MnO2-NPs + REO co-treatment) for 56 days. MnO2-NP exposure caused testicular injury, marked by elevated lipid peroxidation (↑malondialdehyde, ↑nitric oxide), suppressed antioxidants (↓total antioxidant capacity, ↓catalase, ↓glutathione), impaired sperm parameters (motility, count, morphology), and altered serum hormone levels (follicle-stimulating hormone, luteinizing hormone, testosterone). These effects correlated with downregulated steroidogenesis genes (StAR, HSD-3β, CYP11A1). Both Protective and Therapeutic REO treatment mitigated MnO2-NPs oxidative stress, restored hormonal balance, and normalized gene expression. Histopathology revealed reduced seminiferous tubule degeneration and enhanced spermatogenesis in REO groups. Findings demonstrate REO’s efficacy in alleviating MnO2-NPsinduced reproductive toxicity via antioxidant and steroidogenic modulation, positioning REO as a promising therapeutic against nanomaterial-induced gonadotoxicity.

The online version contains supplementary material available at 10.1038/s41598-025-06345-7.