Abstract
BackgroundWe examined the presence and function of tachykinins and the tachykinin-degrading enzymes neprilysin (NEP) and neprilysin-2 (NEP2) in human spermatozoa.MethodsFreshly ejaculated semen was collected from forty-eight normozoospermic human donors. We analyzed the expression of substance P, neurokinin A, neurokinin B, hemokinin-1, NEP and NEP2 in sperm cells by reverse-transcriptase polymerase chain reaction (RT-PCR), western blot and immunocytochemistry assays and evaluated the effects of the neprilysin and neprilysin-2 inhibitor phosphoramidon on sperm motility in the absence and presence of tachykinin receptor-selective antagonists. Sperm motility was measured using WHO procedures or computer-assisted sperm analysis (CASA).ResultsThe mRNAs of the genes that encode substance P/neurokinin A (TAC1), neurokinin B (TAC3), hemokinin-1 (TAC4), neprilysin (MME) and neprilysin-2 (MMEL1) were expressed in human sperm. Immunocytochemistry studies revealed that tachykinin and neprilysin proteins were present in spermatozoa and show specific and differential distributions. Phosphoramidon increased sperm progressive motility and its effects were reduced in the presence of the tachykinin receptor antagonists SR140333 (NK1 receptor-selective) and SR48968 (NK2 receptor-selective) but unmodified in the presence of SR142801 (NK3 receptor-selective).ConclusionThese data show that tachykinins are present in human spermatozoa and participate in the regulation of sperm motility. Tachykinin activity is regulated, at least in part, by neprilysins.
Highlights
We examined the presence and function of tachykinins and the tachykinin-degrading enzymes neprilysin (NEP) and neprilysin-2 (NEP2) in human spermatozoa
Results mRNA expression of tachykinins and neprilysins in human sperm The genes that encode substance P (SP)/neurokinin A (NKA) (TAC1), neurokinin B (NKB) (TAC3), hHK-1(TAC4), NEP (MME) and NEP2 (MMEL1) were detected in cDNAs from human sperm, testis and the pool of 20 human tissues used as positive control (Fig. 1)
The mRNAs of TAC4 and MME were only visualized after cDNA reamplification
Summary
We examined the presence and function of tachykinins and the tachykinin-degrading enzymes neprilysin (NEP) and neprilysin-2 (NEP2) in human spermatozoa. There is convincing evidence that tachykinins are involved in the regulation of reproductive function [1,2,3,4,5,6,7,8]. Recent data have demonstrated that tachykinin receptors are present in human sperm and are functionally active suggesting a role for the tachykinin system in the regulation of sperm function [9]. Tachykinins are the products of three different genes. The TAC1 gene gives rise to four different mRNA splicing isoforms (a, b, g and δ) that encode SP (a, b, g and δ) and NKA (b and g).
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