Role of isoprostanes in human male infertility

Figures & data

Table 1. Oxidative damages to the molecular targets of reactive oxygen species.

Molecular target for reactive oxygen species	Main oxidative damage to biomolecules
Lipids	Lipid peroxidation
Nucleic acids	Hydroxylation of nucleic acid bases, base adducts single and double stranded breaks, DNA- protein cross links
Proteins	Amino acids oxidation, disulfide bonds

Figure 1. Chemical structures of arachidonic acid and F₂-isoprostane series. Isoprostanes are named based upon the structure of the functional groups on the cyclopentane ring in a manner analogous to that of prostaglandins. F₂-isoprostanes (F₂-IsoPs) are F₂-prostaglandin-like compounds formed from the free radical-catalyzed peroxidation of arachidonic acid (ARA). Based on the mechanism of formation, four F₂-IsoP series are generated. The four F₂-IsoP series are named (5, 8, 12, and 15 series) according to the carbon number on which the side chain hydroxyl group is attached, carboxyl carbon being 1. In the figure, chemical structure of ARA and F₂-IsoP series are shown.

Figure 2. Synthesis of F₂-isoprostanes from arachidonic acid esterified in membrane phospholipids. In contrast to cyclooxygenase-derived prostaglandin that are generated from free arachidonic acid (ARA), F₂-isoprostanes (F₂-IsoPs) are initially formed from the oxidation (free-radical-induced peroxidation) of ARA esterified in membrane phospholipids (in the figure, membrane phospholipid bilayer with esterified ARA and F₂-IsoPs are shown). F₂-IsoPs can then be released from the phospholipid backbone as free fatty acids (free F₂-IsoPs in the figure) by phospholipase action (Phospholipase A₂ activity, in the figure).

Figure 3. F₂-IsoP formation is valuable in both spermatozoa and seminal plasma. Upon semen fractionation (by centrifugation) into its seminal plasma and spermatozoa, F₂-isoprostanes (F₂-IsoPs) levels were determined, as free F₂-IsoPs and esterified F₂-IsoPs, respectively. According to the mechanism shown in Figure 2 and the text, in seminal plasma free F₂-IsoPs can be released from the phospholipid backbone of sperm (or other different cell) membrane; in spermatozoa, F₂-IsoPs can be detected as still esterified to phospholipid.

Table 2. Current relevant findings on isoprostanes in male infertility.

Isoprostane detection	Subjects	Findings	Authors
Seminal 8-iso-PGF2α	Infertile men	Negative correlation with sperm motility and morphology	Khosrowbeygi and Zarghami (2007)
Urinary 8-iso-PGF2α	Men with leukocytospermia or oligozoospermia	Marker of oxidative stress	Kullisaar et al. (2013), Punab et al. (2013)
Seminal F2-IsoPs	Patients with oligoasthenozoospermia	Marker of seminal oxidative stress	Nadjarzadeh et al. (2014)
Seminal 8-iso-PGF2α	Infertile men	Marker of sperm oxidative stress (normal, mild, severe)	Mishra et al. (2016)
8-isoprostane	Infertile men after exercise training	Marker of seminal inflammation and oxidative stress	Hajizadeh Maleki and Tartibian (2018)
Seminal F2-IsoPs	Infertile men with varicocele	Increased levels, positive correlation with sperm immaturity	Collodel et al. (2018)
Seminal 8-iso-PGF2α	Infertile men with varicocele	Immunolocalization. The fluorescent label was localized in the cytoplasm surrounding the head and coiled tails of immature sperm
	Infertile men with idiopathic infertility	Immunolocalization.The fluorescent signal was weakly localized in the neck region and sometimes along the tail
Urinary 8-iso-PGF2α	Male partners of couples attending fertility treatment	No significant associations with reproductive outcomes	Rosen et al. (2019)
Seminal F2-IsoPs	Infertile man with globozoospermia	Increased levels both in semen and sperm pellet In immunofluorescence: a strong label around the sperm head and in the cytoplasmic residue	Moretti et al. (2019)
Seminal F2‐IsoPs	Infertile men with varicocele and leukocytospermia	Increased levels	Collodel et al. (2020a)

Notes: 8-iso-Prostaglandin F_2α, 8-iso-PGF_2α; F₂-Isoprostanes, F₂-IsoPs. In the examined studies, 8-isoprostane, 8-iso-PGF_2α, and F₂-IsoPs are used as synonyms and are referred to the same isoprostane isomer produced by the non-enzymatic peroxidation of arachidonic acid.

Figure 4. Immunofluorescence staining of spermatozoa using an anti8-iso-PGF2α polyclonal antibody and 4,6‐Diamidino‐2‐phenylindole (DAPI) solution. (A) sperm from an idiopathic infertile patient show a weak label of anti8-iso-PGF_2α in the sperm tail, the signal appears more evident at the level of the mitochondrial sheath. The nuclei are staining with DAPI. In (B), showing spermatozoa from an infertile varicocele patient, the anti8-iso-PGF_2α staining is located in the tail and in presence of cytoplasmic droplets (arrow). The nuclei stained with DAPI are altered. In (C), spermatozoa of a globozoospermic patient are shown; the nuclei appear perfectly round as evidentiated by DAPI, the anti8-iso-PGF_2α fluorescent label is strongly evident in the tails, sometimes coiled, and in the abundant cytoplasmic residues surrounding the round heads. A, B: bar 5 µm, C: bar 7 µm.

Khosrowbeygi A, Zarghami N. 2007. Levels of oxidative stress biomarkers in seminal plasma and their relationship with seminal parameters. BMC Clin Pathol. 7:6.

 PubMedGoogle Scholar

Kullisaar T, Türk S, Kilk K, Ausmees K, Punab M, Mändar R. 2013. Increased levels of hydrogen peroxide and nitric oxide in male partners of infertile couples. Andrology. 1(6):850–858.

 PubMed Web of Science ®Google Scholar

Punab M, Kullisaar T, Mändar R. 2013. Male infertility workup needs additional testing of expressed prostatic secretion and/or post-massage urine. PLoS One. 8(12):e82776.

 PubMed Web of Science ®Google Scholar

Nadjarzadeh A, Shidfar F, Amirjannati N, Vafa MR, Motevalian SA, Gohari MR, Nazeri Kakhki SA, Akhondi MM, Sadeghi MR. 2014. Effect of coenzyme Q10 supplementation on antioxidant enzymes activity and oxidative stress of seminal plasma: a double-blind randomised clinical trial. Andrologia. 46(2):177–183.

 PubMed Web of Science ®Google Scholar

Mishra S, Kumar R, Malhotra N, Singh N, Dada R. 2016. Mild oxidative stress is beneficial for sperm telomere length maintenance. World J Methodol. 6(2):163–170.

 PubMedGoogle Scholar

Hajizadeh Maleki B, Tartibian B. 2018. Resistance exercise modulates male factor infertility through anti-inflammatory and antioxidative mechanisms in infertile men: a RCT. Life Sci. 203:150–160.

 PubMed Web of Science ®Google Scholar

Collodel G, Moretti E, Longini M, Pascarelli NA, Signorini C. 2018. Increased F2-isoprostane levels in semen and immunolocalization of the 8-iso prostaglandin F2α in spermatozoa from infertile patients with varicocele. Oxid Med Cell Longev. 7508014:2018.

 Google Scholar

Rosen EM, Mínguez-Alarcón L, Meeker JD, Williams PL, Milne GL, Hauser R, Ferguson KK, EARTH Study Team. 2019. Urinary oxidative stress biomarker levels and reproductive outcomes among couples undergoing fertility treatments. Hum Reprod. 34(12):2399–2409.

 PubMed Web of Science ®Google Scholar

Moretti E, Collodel G, Salvatici MC, Belmonte G, Signorini C. 2019. New insights into sperm with total globozoospermia: increased fatty acid oxidation and centrin1 alteration. Syst Biol Reprod Med. 65(5):390–399.

 PubMed Web of Science ®Google Scholar

Collodel G, Castellini C, Chung-Yung Lee J, Signorini C. 2020a. Relevance of fatty acids to sperm maturation and quality. Oxid Med Cell Longev. 7038124:2020.

 Google Scholar