A study published in the journal Antioxidants finds that tobacco smoking can negatively affect semen quality by inducing stress responses in sperm cells.
Study: Smoking Induces a Decline in Semen Quality and the Activation of Stress Response Pathways in Sperm. Image Credit: Oteera / Shutterstock
Infertility is a leading public health problem, affecting 8-12% of reproductive-aged couples worldwide. Male infertility is a significant contributing factor in almost 50% of all infertility cases. Genetic, hormonal, and reproductive system defects are primarily responsible for male infertility. Moreover, several lifestyle factors, such as smoking and alcohol consumption, lack of physical activity, and poor dietary habits, can reduce semen quality and induce sperm DNA damage by inducing oxidative stress and inflammation.
Unfolded protein response (UPR) is a cellular defense mechanism to reduce protein-folding stress in the endoplasmic reticulum (ER). In stressful cellular conditions, UPR is activated in cytosol, ER, or mitochondria due to the accumulation of unfolded or misfolded proteins. In this context, evidence indicates that UPR can be activated in spermatozoa in response to oxidative stress.
In this study, scientists have explored the effects of several lifestyle factors on semen parameters and determined the activation of stress response pathways in sperm cells in response to stressful conditions.
A total of 30 healthy male volunteers of reproductive age were recruited for the study at a hospital in Portugal. Face-to-face interviews were conducted to collect information from the participants about their demographic characteristics, socioeconomic status, dietary habits, and lifestyle. Reproductive health-related information was also collected from the participants.
The participant-provided semen samples were analyzed for overall semen quality (volume, concentration, total count, total motility, and morphology) and sperm motility, concentration, and morphology. Moreover, expressions of antioxidant enzymes and heat-shock proteins (HSPs) were examined in sperm cells to study the activation of stress response pathways.
Among study participants, 47%, 53%, and 57% reported regular smoking, alcohol consumption, and physical activity habits, respectively. About 37%, 40%, and 27% of participants respectively had sperm concentration, sperm count, and sperm progressive motility below the reference values set by the World Health Organization (WHO). About 47% of participants had at least one semen quality parameter below the reference values.
Regarding dietary habits, the most frequently consumed beverage was coffee (77%), followed by bottled water (64%). About 90% of participants reported consuming fresh vegetables, fruits, or fruit juice 1-3 times per week or daily. About 60% of participants reported consuming eggs, poultry, and fresh or frozen fish on average 1-3 times per week.
Association between lifestyle factors and semen quality
Among various lifestyle factors, including tobacco smoking, alcohol consumption, diet, and physical activity, only tobacco smoking significantly negatively impacted semen quality parameters. Specifically, significantly lower semen volume and total sperm count were observed among smokers compared to that among non-smokers.
A non-significant reduction in normal sperm morphology and total sperm motility was observed among smokers compared to that among non-smokers.
Stress response pathways
The expressions of various stress-related proteins, including heat-shock factor 1 (HSF1), heat-shock protein 90 (HSP90), heat-shock protein 27 (HSP27), and phosphorylated HSP27, and antioxidant enzymes, including superoxide dismutase 1 (SOD1), mitochondria SOD (SOD2), and phospholipid hydroperoxide glutathione peroxidase (GPx4), were measured among smokers and non-smokers.
Among these proteins, HSP27 and phosphorylated HSP27 showed significantly elevated expressions among smokers. No significant differences in expressions of other proteins were observed between smokers and non-smokers.
The study highlights the negative impact of tobacco smoking on sperm quality. Poor sperm quality is a major contributing factor for male infertility. The study also indicates the activation of heat shock response in sperm cells by tobacco smoking.
As mentioned by the scientists, a decline in sperm quality due to tobacco smoking might be explained by the increase in protein aggregation in sperm cells and subsequent activation of the stress response pathways.