Metallothionein binding zinc inhibits nuclear chromatin decondensation of human spermatozoa

A TEM-traceable physiologically functional gold nanoprobe that permeates non-endocytic cells

Background

Nanoparticles’ intracellular fate requires proper internalization. Most cells make use of a battery of internalization pathways, but some are practically sealed, as they lack the biochemical machinery for cellular intake. Non-endocytic cells, such as mammals’ spermatozoa, challenge standard drug-delivery strategies.

Purpose

In this article, we present a gold nanoprobe that permeates the external and internal membranes of human sperm.

Methods

Our design makes use of a gold nanoparticle functionalized with a membrane-permeable cysteine-rich recombinant protein. The chimeric protein contains two units of physiologically active metallothioneins (MT) that also provide binding motifs to gold and a cell-penetrating-peptide sequence (CPP) that confers cell permeability to the nanoparticle.

Results

Transmission electron microscopy, indirect immunofluorescence, and functional assays show that the nanoprobe is readily internalized in sperm, without compromising cell integrity, while preserving MT’s physiological activity. Our findings highlight the potential of CPP-functionalized nanogold for investigating the physiology of otherwise impermeable non-endocytic cells.

Zinc sulphate and vitamin E alleviate reproductive toxicity caused by aluminium sulphate in male albino rats

This study was designed to investigate the reproductive toxicity of aluminium sulphate and the therapeutic effects of administration of zinc sulphate and vitamin E individually or in combination against the toxic effect caused by aluminium (Al) in male albino rats. The animals were divided into five groups: group 1 received distilled water and served as control; group 2 received only aluminium sulphate (50 mg/kg body weight (b.w.)); group 3 received aluminium sulphate (50 mg/kg b.w.) plus zinc sulphate (50 mg/kg b.w.); group 4 received aluminium sulphate (50 mg/kg b.w.) and vitamin E (15 mg/kg b.w.); group 5 received aluminium sulphate plus a combination of zinc sulphate and vitamin E in similar doses as above. Doses were administered orally once daily for 45 consecutive days. The results revealed that aluminium sulphate induced significant decrease in body weight gain and testis weight and significant increase in Al level in both serum and testes of male rats. Biochemical analysis showed significant decrease in serum total protein and phospholipids levels, while serum total lipid was significantly elevated post Al treatment. In addition, significant decrease in total protein, phospholipids and cholesterol levels in the testes of Al-treated rats was recorded. The data also showed significant decrease in the levels of serum testosterone, leutinizing hormone and follicle stimulating hormone and significant increase in the level of serum prolactin in Al-intoxicated rats. Moreover, histological examination showed that aluminium sulphate caused apparent alterations in the testicular structure of the treated animals. Treatment with zinc sulphate and vitamin E individually or in combination ameliorated the harmful effects of Al, which was proved histopathologically by the noticeable improvement in the testicular tissues. We can conclude that the tested dose of aluminium sulphate induced toxic effect on the reproductive system of male albino rats and the treatment with zinc sulphate and/or vitamin E alleviated these toxic effects. In some cases, vitamin E exerted a more potent effect, while in other cases, the more potent effect is related to zinc sulphate and the combination of both at most of the recorded data.

Addition of zinc to human ejaculate prior to cryopreservation prevents freeze-thaw-induced DNA damage and preserves sperm function

PURPOSE

To study the effect of addition of zinc to human semen sample prior to cryopreservation on post-thaw sperm quality and function.

METHODS

Semen samples were collected from men attending university infertility clinic for semen analysis (n=109). Liquefied semen samples were cryopreserved in glycerol-egg yolk- citrate medium with or without the prior addition of zinc (100 μM) and stored in liquid nitrogen. After 10 days, the semen samples were thawed to assess the outcome. Sperm motility, DNA integrity, mitochondrial potential and the ability of spermatozoa to undergo capacitation and acrosome reaction was assessed in post-thaw samples.

RESULTS

Semen samples cryopreserved after addition of zinc had a significantly higher percentage of sperm with intact DNA (p<0.001), mitochondrial function (p<0.001) and progressive motility (p<0.01) compared to the semen samples cryopreserved without zinc supplementation. Apart from this, ability to undergo capacitation and acrosome reaction in vitro was significantly higher in semen samples cryopreserved with zinc (p<0.0001 and p<0.001 respectively).

CONCLUSIONS

Addition of zinc to semen samples prior to cryopreservation helps in preventing the freeze-thaw-induced sperm DNA damage and loss of sperm function.

Seminal immune response in infertile men with leukocytospermia: effect on antioxidant activity

OBJECTIVE

To investigate the incidence of leukocytospermia and relation to T helper cytokines, tumor necrosis factor alpha (TNFalpha) and interleukin-4 (IL-4), antisperm antibodies and antioxidant activity.

DESIGN

Semen samples from 176 infertile men and 24 fertile controls were investigated.

METHODOLOGY

The protocol included tubal patency test, hysterosalpingography and laparoscopy and dye test and ovulation through mid-luteal phase progesterone for the wives. The husbands had semen analysis, cytomorphology evaluation and semen culture. Seminal TNFalpha and IL-4, antisperm antibodies, total antioxidant activity, superoxide dismutase and zinc were determined.

RESULTS

Leukocytospermia occurred in 44.3% of the infertile men compared to 12.5% of the fertile men (P<0.01). Thirty-six (20.5%) men had pathogenic bacterial organisms which constituted 46.2% of those with leukocytospermia. Sperm parameters were worse with leukocytospermia in terms of sperm count (P<0.01), total motility progressive motility (P<0.01), morphology, asthenozoospermia, sperm membrane integrity and antisperm antibodies. TNFalpha and IL-4 had an inverse relationship; the expression of TNFalpha was higher with leukocytospermia and bacteriospermia (P<0.001), while IL-4 was higher in fertile controls (P<0.005). Incidence of antisperm antibodies was higher with leukocytospermia. Total antioxidant activity, superoxide dismutase and zinc were lower with leukocytospermia.

CONCLUSION

Leukocytospermia impairs sperm function through reduced antioxidant activity and enhanced T helper 1 modulation.

In vitro inhibition of superoxide anion production and superoxide dismutase activity by zinc in human spermatozoa

The in vitro effect of zinc on superoxide anion (O2-) generation and on SOD-like activity in spermatozoa of infertile men was investigated. The formation of superoxide anion was stimulated by NADPH and the level of superoxide anion was measured by the reduction of ferricytochrome c. Both Percoll-isolated (n = 14) and washed spermatozoa (n = 14) exposed to 1 mmol/L zinc (60 min, 37 degrees C), released less (p < 0.002 and p < 0.04, respectively) superoxide anions than did zinc-untreated spermatozoa. These results implicate a possible role for zinc as a scavenger of excessive superoxide anions produced by defective spermatozoa in semen after ejaculation. Additionally, zinc was found to dose-dependently inhibit superoxide dismutase (SOD)-like activity of spermatozoa in vitro. The inhibition of SOD-like activity by an equal concentration of zinc (1 mmol/L) was less pronounced in oligospermic (p < 0.002; n = 16) and asthenozoospermic (p < 0.0005; n = 20) than in normozoospermic samples (p < 0.0001; n = 20). This differential ability of zinc to inhibit SOD-like activity may be relevant to the physiological function of spermatozoa in fertilization. The evidence that zinc may elicit an inhibition of both superoxide anion production and SOD-like activity in human spermatozoa, indicate the existence of novel, zinc-related mechanism(s) involved in the oxidative events occurring after ejaculation, with a possible modulatory effect on germ cell function.

In vitro effect of zinc on oxidative changes in human semen

The in vitro effect of zinc on superoxide anion (O2-) generation and on experimentally induced lipid peroxidation (LPO) in spermatozoa of infertile men was investigated. Washed spermatozoa pre-incubated for 30 min at 37 degrees C in the presence of 1 or 3 mmol l-1 zinc, released less superoxide anions (P < 0.03 and P < 0.02, respectively; n = 9) than the untreated spermatozoa. Similar results were obtained using activated polymorphonuclear leukocytes (1 x 10(6) cells ml-1) in the presence of 1 or 3 mmol l-1 Zn (P < 0.001 and P < 0.0002, respectively; n = 9). The in vitro evidence of the inhibitory effect of zinc on O2- generation by human spermatozoa and leukocytes indicates that zinc may act in vivo as a scavenger of excessive O2- production by defective spermatozoa and/or leukocytes in semen after ejaculation. A significant stimulatory effect of Zn (3 mmol l-1) on iron-induced lipid peroxidation, measured by the formation of thiobarbituric acid reactive substances (TBARS), was detected in the spermatozoa of 16 normo- and 17 asthenozoospermic males (P < 0.0001 and P < 0.001, respectively). In 11 samples with sperm concentration 20.3 +/- 2.1 x 10(6) ml-1, exhibiting initial TBARS concentration two times higher than in normo- and asthenozoospermic samples (40.5 +/- 2.4 vs. 17.1 +/- 1.1 and 28.5 +/- 4.1 nmoles TBARS 10(-8) spermatozoa), no effect of zinc on the LPO rate was found. The observed inhibitory effect of zinc on superoxide anion regardless of the initial O2- level and stimulatory effect of zinc depending on the initial LPO rate in human spermatozoa suggests that this metal ion participates in the oxidative changes occurring after ejaculation and thus may modulate the properties of germ cells.

Treatment of asthenozoospermia with zinc sulphate: andrological, immunological and obstetric outcome

OBJECTIVES

The role of zinc therapy on infertility caused by defective sperm quality is examined.

STUDY DESIGN

In this study, 100 men with asthenozoospermia were randomised into two groups--250 mg twice daily zinc therapy for 3 months and no therapy. The patients were followed up for another 6 months. Sperm parameters, circulating antisperm antibodies, sex hormones and T helper cytokines were evaluated before and after treatment for the two groups.

RESULTS

There was significant improvement in the sperm quality; sperm count (P<.02), progressive motility (P<.05), fertilising capacity (P<.01) and a reduction in the incidence of antisperm antibodies (P<.01). Zinc/cadmium was higher in the zinc therapy group (P<.02). T helper cytokine, interleukin-4 level was significantly higher after zinc therapy (P<.02) while TNFalpha showed a significant decrease (P<.05).

CONCLUSIONS

Zinc therapy has a role in improving sperm parameters in men with asthenozoospermia, probably through its membrane stabilising effect as an antioxidant and its effect on cellular and humoral immunity by reducing the levels of antisperm antibodies and TNFalpha and increasing that of IL-4.