A novel epididymal quiescence factor inhibits sperm motility by modulating NOS activity and intracellular NO-cGMP pathway

Purification and partial characterization of a sperm motility-inhibitory protein of ram cauda epididymal plasma

Mammalian sperm remain quiescent but fertile for several weeks in cauda epididymis. Although several sperm quiescent factors of epididymal plasma have been identified in goat, pig and cattle; however, little is known in sheep. In the present study, purification and characterization of a novel sperm quiescent protein of ovine cauda epididymal plasma (CEP) was carried out. The sperm quiescent protein was partially purified by hydroxyapatite gel adsorption chromatography followed by DEAE-sepharose® anion exchange chromatography. In the latter, the sperm quiescent activity was eluted both in 0.05 and 0.2 M potassium phosphate buffer (pH 7.5) fractions having a predominant protein of about 80 and 70 kDa with 87% and 63% homogeneity, respectively. The proteins were designated as motility-inhibitory factor of sheep I and II (MIFS-I and II), respectively. Significant (about 60%) inhibition of sperm motility was observed following treatment of cauda epididymal sperm with 6 and 12 µg/mL of partially purified MIFS-I and II, respectively. Specific activities of the partially purified MIFS-I and II were 563 and 261 U/mg of protein, while the fold-purification of the activity were 5119 and 2373, respectively. Both the proteins were heat-labile and the activity was completely lost following incubation at 100°C for 5 min. Further, the partially purified MIFS-I (5 µg/mL) caused significant reduction in in vitro sperm capacitation and slight decline in tyrosine phosphorylated p72 and p52 proteins; however the protein was nontoxic to sperm. Mass spectrometric analysis of MIFS-I revealed significant identity with human semaphorin 3D. Both dot blot and western blot analysis demonstrated cross-reactivity of MIFS-I with polyclonal anti-human SEMA3D antibody. It was concluded that the MIFS-I of ovine CEP was putative ovine semaphorin 3D protein having potent sperm quiescent and decapacitating activities and it possibly acts through inhibition of protein tyrosine phosphorylation.

The Activated AMPK/mTORC2 Signaling Pathway Associated with Oxidative Stress in Seminal Plasma Contributes to Idiopathic Asthenozoospermia

Asthenozoospermia is a common form of abnormal sperm quality in idiopathic male infertility. While most sperm-mediated causes have been investigated in detail, the significance of seminal plasma has been neglected. Herein, we aimed to investigate the possible pathogenic factors leading to decreased sperm motility based on seminal plasma. Semen was collected from normo- (NOR, n = 70), idiopathic oligo- (OLI, n = 57), and idiopathic asthenozoospermic (AST, n = 53) patients. Using attenuated total reflection-Fourier transform infrared coupled with chemometrics, distinct differences in the biochemical compositions of nucleic acids, protein structure (amides I, II, and III), lipids, and carbohydrates in seminal plasma of AST were observed when compared to NOR and OLI. Compared with NOR and OLI, the levels of peptide aggregation, protein phosphorylation, unsaturated fatty acid, and lipid to protein ratio were significantly increased in AST; however, the level of lipid saturation was significantly decreased in seminal plasma of AST. Compared with NOR, the levels of ROS, MDA, 8-iso-prostaglandin F2α (8-isoPGF2α), and the ratio of phospho-AMPKα/AMPKα1 were significantly increased in AST; however, the levels of SOD, glutathione S-transferase (GSTs), protein carbonyl derivative (PC), and the ratio of phospho-Rictor/Rictor were significantly decreased in seminal plasma of AST. Changes of the AMPK/mTORC2 signaling in the seminal microenvironment possibly induce abnormal glucose and lipid metabolism, which impairs energy production. Oxidative stress potentially damages seminal plasma lipids and proteins, which in turn leads to impaired sperm structure and function. These findings provide evidence that the changes in seminal plasma compositions, oxidative stress, and activation of the AMPK/mTORC2 signaling contribute to the development of asthenozoospermia.

Production of bioactive recombinant ovine cysteine-rich secretory protein 1 in Escherichia coli

Ovine cysteine-rich secretory protein 1 (CRISP-1) is an acidic glycoprotein of epididymal origin under CRISP, antigen 5, pathogenesis-related protein 1 (CAP) super-family. The aim of the present study was the optimization of bacterial production and partial characterization of putative mature ovine CRISP-1 protein. The cDNA corresponding to T^{23 -} C²⁴² peptide fragment of ovine CRISP-1 protein was cloned into THE pET32b(+) expression vector using E. coli DH5α. Protein expression was carried out in E. coli BL21(DE3) by inducition with 1 mM IPTG at 37°C for 4 h. The recombinant protein was expressed as inclusion bodies and purified by Ni-NTA affinity chromatography using a pH gradient. Further purification of the protein was carried out by gel extraction following zinc sulfate negative staining. SDS-PAGE analysis of the purified recombinant CRISP-1 protein revealed a 43.8 kDa band. Bioactivity of the purified CRISP-1 protein was examined on sperm motility and capacitation. The recombinant ovine CRISP-1 protein at 5 µg/ml caused significant inhibition of sperm motility, and the activity was lost following heating the protein at 100°C for 5 min. The protein also demonstrated decapacitation activity, and at a concentration of 2 µg/ml, it caused a significant (P < 0.05) reduction in sperm capacitation. In conclusion, the thioredoxin-tagged ovine CRISP-1 protein was successfully produced in E. coli and purified in the soluble form by a combination of Ni-NTA affinity chromatography, gel purification, and dialysis. The recombinant protein exhibited both motility-inhibiting and decapacitating activities. Further study is needed to elucidate the mechanism of action and evaluate it's possible use in semen preservation.Abbreviations: CRISP-1: Cysteine-rich secretory protein-1; PCR: polymerase chain reaction; IPTG: isopropyl-β-D-thiogalactopyranoside; LB: Luria Bertani; SDS-PAGE: sodium dodecyl sulfate polyacrylamide gel electrophoresis; EDTA: ethylene diamine tetraacetic acid; Ni-NTA: Nickel nitrilotriacetic acid.

Effect of nitroso-redox imbalance on male reproduction

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are byproducts of normal metabolic processes. They are necessary for normal cellular function and are kept in balance by antioxidant mechanisms. Alterations in levels of ROS and RNS can lead to nitroso-redox imbalance that in turn can negatively affect male reproduction. Strategies to decrease ROS/RNS involve evasion of exposures (smoking, meat intake, pollution, calorie-dense diet), managing lifestyle, and increasing the consumption of antioxidants (vitamin C, vitamin E, alpha-lipoic acid, taurine, quercetin). Targeted therapies focusing on nitroso-redox imbalance can be critical for treatment of male reproductive dysfunction. This review outlines endogenous and exogenous sources of ROS/RNS, adverse effect on male reproduction, and strategies to control nitroso-redox imbalance.