Study On The Toxicity Of Aluminum To Sperm Mitochondrial Cytochrome Oxidase Subunits ??? And ? In Male Rats

Objective:To study the effects of aluminum exposure on sperm mitochondrial cytochrome oxidase subunits I,II and III?COX??COX??COX??,and to explore the mechanism of mitochondria and sperm damage that caused by aluminum.Aim to provide a theoretical basis for clinical prevention and treatment of male sperm quality decline caused by aluminum.Methods:According to the median lethal dose of Al Cl₃·6H₂O in drinking water,48healthy male Wistar rats?SPF grade?weighing 130?150g at 6 weeks of age were divided into four groups randomly and averagely.Three doses of aluminum exposure groups?1/20,1/10,1/5 LD50?and blank control group were established.Aluminum was added by drinking water,and the doses were:control group[pure water,0 mg/?kg·d?],low dose group[1/20LD50,64.18mg/?kg·d?],medium dose group[1/10 LD50,128.36mg/?kg·d?]and high dose group[1/5 LD50,256.72 mg/?kg·d?].Treated for 110 days.Then samples were collected,testis and epididymis were weighed and viscera coefficients were calculated.Sperm quality parameters were detected by Computer-aided sperm analysis.The expression of COX?,COX?,COX?m RNA were determined by real-time fluorescent quantitative polymerase chain reaction?RT-PCR?.The sequences of COX?,COX?and COX?gene were directly sequenced after amplification by polymerase chain reaction?PCR?,and the sequences were compared with the reference sequences provided on NCBI by Bioedit software to analyze whether exposure to aluminum can cause mutations in mitochondrial COX?,COX?,COX?genes.Results:In terms of viscera damage,the body weight and testicle weight of the rats in low dose group were lower than that in control group?P<0.05?.The body weigh,testicle and epididymis weight and viscera coefficient of the rats in medium and high dose groups were all lower than that in control group?P<0.05?.The results of sperm quality test showed that the percentage of progressively motile sperm was significantly decreased in the low,medium and high dose groups compared with that in the control group?P<0.05?,while the percentage of dead sperm was significantly higher than that in the control group?P<0.05?,Moreover,as the dose of aluminum increases,the effects of these damages become more obvious.Spearman correlation analysis showed that aluminum exposure dose was moderately negatively correlated with the body weight,testicular weight,testicular viscera coefficient and epididymal viscera coefficient?P<0.001?.And it was highly negatively correlated with the epididymis weight,the percentage of progressive sperm and the expression of COX?,COX?and COX?m RNA?P<0.001?;At the same time,highly positively correlated with the percentage of dead sperm?P<0.001?.The results of real-time fluorescent quantitative polymerase chain reaction showed that,as compared with control group,the relative m RNA expression of COX?,COX?,COX?genes was deceased in varying degrees in low,medium and high dose groups,the difference was statistically significant?P<0.05?.The effects of these damages become more obvious as the dose increases.The sequenced results of COX?,COX?,COX?genes showed that mutations of three samples were detected in the low,medium and high dose groups.One sample occurred a C8812T mutation of COX?gene in low dose group,one sample occurred the same mutation?C8812T?of COX?gene in medium dose group,and one sample occurred four mutations in COX?,COX?,COX?genes in high dose groups:COX??T5715C,C5940T?,COX??G7499A?,COX??T8962C?.There was not any mutations been found in the control group.Conclusion:Exposure to aluminum can do harm to sperm mitochondrial COX?,COX?,COX?genes,leading to a significant decrease in m RNA expression of these genes and causing genetic mutations in some of it.Resulting in male reproductive toxicity and a decline in sperm quality.