Table 2.

Effects of tobacco smoking, alcohol consumption and drug addiction on spermatogenesis and sperm parameters

	Studies in humans	Animal studies
Tobacco smoking	Reduction of sperm concentration [26, 27] Impairment of sperm motility [17] Increase in ultra-structural abnormalities (axonemal microtubules and tail alterations) [28, 29] Impairment of mitochondrial activity and chromatin structure [17, 33, 34] Impairment of acrosome reaction and capacitation [30, 31] Increase of DNA methylation patterns [49] Alterations in ERK1/2, nuclear factor-κB signal pathway [44] Reduction of creatine kinase activity in sperm [55–57]	Increase in apoptosis via extrinsic (FAS, FASL) or mitochondrial processes (BCL, caspase-3) in rats [39, 40] Reduction of antioxidant activity in rats [40] Increase in DNA damage in sperm rats [41, 42]; of DNA methylation patterns PEBP1 gene in rats [44] Reduction of sperm count and motility in rats [45]
Alcohol consumption	Reduction of seminal volume and sperm concentration [58, 61, 62] Impairment of sperm motility and morphology [60, 61] Increased sperm polycyclic aromatic hydrocarbon DNA adducts [72]	Increase in apoptosis (by upregulation of Fas) of spermatogenic cells in rats [68] Alteration of nuclear maturity and DNA integrity in sperm cells of rats [70] Increase in ROS generation and depletion of glutathione pool in testicular tissue of rats [71] Impairment of sperm motility in rats [70]
Drug addiction
Marijuana	Decrease in sperm count [82–84] Impairment of sperm morphology and motility [85, 102, 103] Reduction of spontaneous acrosome reactions [102, 103]	Impaired sperm concentration and morphology in rats [91] Inhibition of sperm ATP production in rats [104] Reduction of fructose and citric acid contents in testis and prostate of male rats [95]
Cocaine	Impairment of sperm counts and motility [86]	Vasoconstriction of testicular blood vessels in rats resulting in ischemic and reperfusion injuries [96] Reduction of diameter of seminiferous tubules [97] Decrease in number of total germ cells [97] Increase in oxidative stress in mice [98]
Opioids	Impaired spermatogenesis [76] Increased rates of DNA fragmentation in humans [89] Reduced expression of catalase-like and superoxide dismutase-like activity [89]	Increase of rates of DNA damage and tubular degeneration in rats [100, 101]
Amphetamines and Ecstasy	No data available	Vasoconstriction of testicular blood vessels in rats [96] Increase in rates of DNA damage and tubular degeneration in rats [99]