Rats exposed to smoke from e-cigarettes experienced altered testicular structure and other indicators of loss of fertility, raising questions about their safety as smoking prevention devices.

While the effects of e-cigarette smoke appeared to not be as severe as that from cigarettes, research published in the Spanish journal Revista Internacional de Andrologia suggested that adult male rats exposed to e-cigarette smoke still experienced many of the harmful reproductive effects of smoking. This was associated with increased oxidative stress in testicular tissue, but did not include significant differences in sperm motility or sperm count.

'Cigarette and EC liquid can increase oxidative stress as well as cause morphological changes in the testicle', concluded the authors, based in Cumhuriyet University and Sivas Numune Hospital in Turkey. They added, 'To be a safe option in smoking cessation studies, its effect on people needs to be enlightened'.

Despite their relatively recent development, e-cigarettes, also known as 'vapes', are used extensively. According to the Office for Health Improvement and Disparities, around seven percent of adults and over eight percent of 11-18 year olds in the UK were vapers in 2021. Tobacco exposure during adolescence in males, could lead to DNA changes in offspring, a recent study showed (see BioNews 1205).

While e-cigarettes are generally considered to be a safer alternative, vaping products can contain nicotine, formaldehyde, and heavy metal compounds which have been associated with poor outcomes. Additionally, a study from 2020 published in the journal Human Reproduction found that men who smoked either cigarettes or e-cigarettes had lower sperm counts than non-smokers.

To gain a better perspective on the biochemical effects of e-cigarettes on reproductive health, 24 adult male rats were exposed to cigarette smoke, e-cigarette vapours, or nothing as a control. Following exposure, the rats were analysed for various measures of reproductive health, including testicular histology, sperm health, and oxidative stress biomarkers.

Some rats exposed to cigarette smoke or e-cigarette vapours displayed 'disorganised seminiferous tubules'. These structures are involved in sperm production, and it is suggested that this altered histology could harm sperm quality. The researchers, though, did not appear to find a significant decrease in sperm count or motility in exposed rat groups. Additionally, relative gonad size was decreased in the cigarette group, but not those exposed to e-cigarette vapours.

However, rats exposed to e-cigarette vapours did appear to show increased levels of oxidative stress biomarkers such as lipid peroxidase, while other markers of stress were higher only in cigarette-treated groups. It has been hypothesised that increased oxidative stress could lead to testicular structural damage, potentially linking e-cigarettes to decreased male fertility. Further research is required to clarify specific mechanisms that may be linking them.

By Dan Jacobson, via Bio News - https://www.progress.org.uk/exposure-to-e-cigarette-vapour-damages-testicles-in-rats/