Paraoxonase-1 is only present in traceable amounts in seminal fluid and does not show any relationship with male subfertility

Abstract

Study Type - Aetiology (case series).

Level of evidence: 4. What's known on the subject? and What does the study add? Oxidative stress seems to be one of the biochemical causes of defective sperm function. Paraoxonases are antioxidant enzymes that degrade lipid peroxides. There is a paucity of data on the possible role played by these enzymes in the pathophysiology of male sub-fertility. The present study shows that testicular tissue of sub-fertile patients clearly expresses paraoxonases-1, 2, and 3. These findings suggest a role for these enzymes in the protection against lipid peroxidation inside the cell. However, the concentration and activity of paraoxonase-1 in semen are negligible and are probably the result of cellular catabolism, with no significant biological function.

Objective: To characterise the immunohistochemical sites of paraoxonase (PON) 1, PON2 and PON3 in human testicular tissue, and to analyse PON1 levels in semen, aiming to investigate the role played by these enzymes in the pathophysiology of male subfertility.

Patients and methods: The present study was performed in 41 semen samples from normal donors and in 52 semen samples and ten testicle biopsies from patients who were being evaluated for causes of subfertility.

Results: Immunohistochemical analyses showed high levels of PON1 and PON3 expression in testicular tissue. PON2 expression was also detected, albeit at weaker levels. Oxidative stress indicators in biopsies were low and localized in some specific areas of the seminiferous tubules. PON1 was detected in seminal fluid at very low levels but with no significant differences between patients and controls. Receiver-operating characteristic analysis showed a low diagnostic power of semen PON1 levels.

Conclusions: The present study shows high protein expression levels of PON1, PON2 and PON3 in testicular cells. The concentrations and activities of PON1 in semen are negligible and are probably the result of cellular catabolism, with no significant biological function in the testes.