Reactive oxygen species

Oxidative stress occurs when the production of potentially destructive reactive oxygen species (ROS) exceeds the bodies own natural antioxidant defenses, resulting in cellular damage. Oxidative stress is a common pathology seen in approximately half of all infertile men. ROS, defined as including oxygen ions, free radicals and peroxides are generated by sperm and seminal leukocytes within semen and produce infertility by two key mechanisms. First, they damage the sperm membrane, decreasing sperm motility and its ability to fuse with the oocyte. Second, ROS can alter the sperm DNA, resulting in the passage of defective paternal DNA on to the conceptus. This review will provide an overview of oxidative biochemistry related to sperm health and will identify which men are most at risk of oxidative infertility. Finally, the review will outline methods available for diagnosing oxidative stress and the various treatments available.

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Oxidative stress and male infertility—a clinical perspective

The use of receiver operating characteristic curves in biomedical informatics

https://uroweb.org/wp-content/uploads/Jungwirth-A-et-al-Eur-Urol-2012-622342-EAU-Guidelines-on-Male-Infertility-the-2012-update.pdf

European Association of Urology Guidelines on Male Infertility: The 2012 Update

BACKGROUND Reported declines in sperm counts remain controversial today and recent trends are unknown. A definitive meta-analysis is critical given the predictive value of sperm count for fertility, morbidity and mortality. OBJECTIVE AND RATIONALE To provide a systematic review and meta-regression analysis of recent trends in sperm counts as measured by sperm concentration (SC) and total sperm count (TSC), and their modification by fertility and geographic group. SEARCH METHODS PubMed/MEDLINE and EMBASE were searched for English language studies of human SC published in 1981-2013. Following a predefined protocol 7518 abstracts were screened and 2510 full articles reporting primary data on SC were reviewed. A total of 244 estimates of SC and TSC from 185 studies of 42 935 men who provided semen samples in 1973-2011 were extracted for meta-regression analysis, as well as information on years of sample collection and covariates [fertility group ('Unselected by fertility' versus 'Fertile'), geographic group ('Western', including North America, Europe Australia and New Zealand versus 'Other', including South America, Asia and Africa), age, ejaculation abstinence time, semen collection method, method of measuring SC and semen volume, exclusion criteria and indicators of completeness of covariate data]. The slopes of SC and TSC were estimated as functions of sample collection year using both simple linear regression and weighted meta-regression models and the latter were adjusted for pre-determined covariates and modification by fertility and geographic group. Assumptions were examined using multiple sensitivity analyses and nonlinear models. OUTCOMES SC declined significantly between 1973 and 2011 (slope in unadjusted simple regression models -0.70 million/ml/year; 95% CI: -0.72 to -0.69; P < 0.001; slope in adjusted meta-regression models = -0.64; -1.06 to -0.22; P = 0.003). The slopes in the meta-regression model were modified by fertility (P for interaction = 0.064) and geographic group (P for interaction = 0.027). There was a significant decline in SC between 1973 and 2011 among Unselected Western (-1.38; -2.02 to -0.74; P < 0.001) and among Fertile Western (-0.68; -1.31 to -0.05; P = 0.033), while no significant trends were seen among Unselected Other and Fertile Other. Among Unselected Western studies, the mean SC declined, on average, 1.4% per year with an overall decline of 52.4% between 1973 and 2011. Trends for TSC and SC were similar, with a steep decline among Unselected Western (-5.33 million/year, -7.56 to -3.11; P < 0.001), corresponding to an average decline in mean TSC of 1.6% per year and overall decline of 59.3%. Results changed minimally in multiple sensitivity analyses, and there was no statistical support for the use of a nonlinear model. In a model restricted to data post-1995, the slope both for SC and TSC among Unselected Western was similar to that for the entire period (-2.06 million/ml, -3.38 to -0.74; P = 0.004 and -8.12 million, -13.73 to -2.51, P = 0.006, respectively). WIDER IMPLICATIONS This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50-60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand. Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed.

Temporal trends in sperm count: a systematic review and meta-regression analysis.

MedCalc: a new computer program for medical statistics

The lipid composition of the sperm membrane has a significant effect upon the functional characteristics of spermatozoa. In the present study we investigated the fatty acid (FA) composition of subpopulations of spermatozoa separated on a discontinuous Percoll gradient (47:90%) and the FA composition of phospholipids (PL) of sperm heads and tails in both normal and abnormal semen samples. In normozoospermic samples, polyunsaturated fatty acids (PUFA) represented 34.0 +/- 1.3 (mean +/- SE, mole %) and 25.6 +/- 1.2% of total FA of PL of the 47 and 90% Percoll fractions respectively. Docosahexaenoic acid (22:6omega3, DHA) contributed to more than 60% of total PUFA. DHA was significantly lower in both the 47% (P < 0.05) and the 90% (P < 0.01) Percoll fractions of oligozoospermic samples and in the 90% Percoll layer of asthenozoospermic samples (P < 0.01), compared with normozoospermic samples. The omega6/omega3 ratio was significantly increased in both Percoll fractions of samples with oligozoospermia (47%, P < 0.001 and 90%, P < 0.001) or with asthenozoospermia (47%, P < 0.05 and 90%, P < 0.001) compared with normozoospermic samples. The oxidative potential index (OPI) of spermatozoa recovered from the 47% Percoll layer was significantly higher (P < 0.0001) than of those recovered from the 90% Percoll. Mean melting point (MMP), an index of membrane fluidity, was significantly lower in head than in tails (P < 0.01) of spermatozoa, and also in both the 47% (P < 0.01) and 90% (P < 0.001) Percoll fractions of normozoospermic samples in comparison with oligozoospermic samples. The MMP was significantly higher (P < 0.05) in samples of patients with idiopathic oligo/asthenozoospermia, varicocele, and male accessory gland infection (MAGI). These differences in FA composition of PL in subpopulations of human spermatozoa, and in their heads and tails may be related to sperm maturity and to differences in physiological function.

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The fatty acid composition of phospholipids of spermatozoa from infertile patients

The presence of various cytokines, namely hepatocyte growth factor (HGF), interleukin-1 receptor antagonist (IL-1 RA), and interleukins (IL-1 alpha, IL-6, and IL-8), as well as the production of reactive oxygen species (ROS) was investigated in seminal plasma of fertile and infertile patients in order to evaluate the possible value of measuring these substances for the diagnosis of male accessory gland infection, and to assess the possible relationship between oxidative stress and cytokines during leucocytospermia and male accessory gland infection (MAGI). Our findings indicate that all of the measured cytokines seem to be produced locally as well as by white blood cells (WBC) and that, due to the presence of higher numbers of WBC, accessory gland infection may exert a deleterious effect on sperm quality through the production of ROS and/or of particular cytokines such as IL-1 alpha, IL-1 RA, and IL-8. The most specific marker for a sensitivity of 95% in discriminating between cases with or without MAGI is the measurement of IL-6 in seminal plasma. In the absence of WBC several cytokines are constitutively produced and correlate with sperm concentration (HGF, IL-8), alpha-glucosidase (IL-6), and gamma-glutamyltransferase activity (HGF). The measurement of these cytokines in semen may provide clinically useful information for the diagnosis of male accessory gland infection, as well as in the absence of WBC where it can provide information about certain mechanisms of male reproductive function and dysfunction.

The relation between reactive oxygen species and cytokines in andrological patients with or without male accessory gland infection.

Receiver operating characteristic curves and accuracy parameters were computed for traditional sperm characteristics (concentration, motility, morphology) and the number of peroxidase negative cells, and the concentration of adenosine triphosphate (ATP) in semen from populations of fertile and infertile men, and men who achieved a pregnancy after varicocele treatment. The percentage and concentration per millilitre of spermatozoa with rapid linear progressive motility, and the ATP concentration, provided the best discrimination between fertile and treated fertile from infertile men. The misclassification rate was higher for sperm morphology, total progressive motility and viability, whereas sperm concentration and the total sperm count per ejaculate had the worst discriminating power. The number of peroxidase negative cells per 100 spermatozoa was highly specific in identifying men who achieved pregnancy after varicocele treatment. The lower limit of normality of sperm characteristics was remarkably different between fertile men and men achieving pregnancy after treatment or during infertility work-up.

Reassessment of the accuracy of traditional sperm characteristics and adenosine triphosphate (ATP) in estimating the fertilizing potential of human semen in vivo

PROBLEM The potential value of assessment of cytokine concentrations for the diagnosis of certain pathological conditions of male reproduction has not been fully evaluated. METHOD The concentrations of interleukin 6 (IL-6, pg/mL), its soluble receptor (IL-6 sR, ng/mL), and of interleukin 1 beta (IL-1 beta, pg/mL) have been measured in semen samples of 114 men and 12 corresponding blood sera. RESULTS The concentration of IL-6 was unrelated to that of its receptor. Both IL-6 and IL-6 sR were higher in the first (mean: 69 and 31 resp.) than in the second fraction (39 and 13) of split ejaculates, and were within normal limits in vasectomised men. The Interleukin 1 beta concentration presented a strong positive correlated with that of IL-6 (r = 0.74, P < 0.001). The concentrations of IL-6 and IL-1 beta were unrelated to sperm concentration, motility and morphology, and they were within normal limits in immunological cases. Both IL-6 and IL-1 beta were higher (P < 0.01) in cases with accessory gland inflammation. CONCLUSIONS Measurement of in particular IL-6 in semen may contribute to the diagnosis of inflammatory disease of the accessory sex glands (positive predictive value = 98%, sensitivity = 72%, specificity = 94%), but it is not relevant for the diagnosis of immunological disease.

Frank Schoonjans

Papers

MedCalc: a new computer program for medical statistics

The fatty acid composition of phospholipids of spermatozoa from infertile patients

The relation between reactive oxygen species and cytokines in andrological patients with or without male accessory gland infection.

Reassessment of the accuracy of traditional sperm characteristics and adenosine triphosphate (ATP) in estimating the fertilizing potential of human semen in vivo

Cytokines in Semen of Normal Men and of Patients With Andrological Diseases