Defective mitochondrial oxidative phosphorylation in varicocele-bearing testicles

Mechanism of mitochondrial oxidative phosphorylation disorder in male infertility

ABSTRACT

Male infertility has become a global concern, accounting for 20-70% of infertility. Dysfunctional spermatogenesis is the most common cause of male infertility; thus, treating abnormal spermatogenesis may improve male infertility and has attracted the attention of the medical community. Mitochondria are essential organelles that maintain cell homeostasis and normal physiological functions in various ways, such as mitochondrial oxidative phosphorylation (OXPHOS). Mitochondrial OXPHOS transmits electrons through the respiratory chain, synthesizes adenosine triphosphate (ATP), and produces reactive oxygen species (ROS). These mechanisms are vital for spermatogenesis, especially to maintain the normal function of testicular Sertoli cells and germ cells. The disruption of mitochondrial OXPHOS caused by external factors can result in inadequate cellular energy supply, oxidative stress, apoptosis, or ferroptosis, all inhibiting spermatogenesis and damaging the male reproductive system, leading to male infertility. This article summarizes the latest pathological mechanism of mitochondrial OXPHOS disorder in testicular Sertoli cells and germ cells, which disrupts spermatogenesis and results in male infertility. In addition, we also briefly outline the current treatment of spermatogenic malfunction caused by mitochondrial OXPHOS disorders. However, relevant treatments have not been fully elucidated. Therefore, targeting mitochondrial OXPHOS disorders in Sertoli cells and germ cells is a research direction worthy of attention. We believe this review will provide new and more accurate ideas for treating male infertility.

The Evolving Landscape of Male Varicocele Pathophysiology in the Era of Multi-Omics: A Narrative Review of the Current Literature

Male-factor infertility is implicated in over half of the millions of cases of infertility worldwide, and varicoceles are the most common correctable cause of male-factor infertility. The pathophysiologic mechanism for varicoceles is complex and next-generation technologies offer promising insights into the molecular underpinnings of this condition. In this narrative review, we highlight historical and contemporary paradigms associated with varicoceles, with an emphasis on the biological underpinnings of this disease. Specifically, we review the literature describing the underlying causes of varicoceles, discuss the molecular and cellular mechanisms causing pathological changes in some (but not all) men, and highlight key articles regarding the next-generation analyses (e.g., transcriptome, epigenome, proteome, and microbiome) being applied to better understand the condition and its treatment. These data demonstrate an ongoing evolution of the knowledge of varicoceles and the potential for improved personalized care in the future for men with this condition.

Perspectives in Pediatric Pathology, Chapter 20. Adolescent Varicocele

Varicocele is characterized by elongation, dilatation, and tortuosity of the veins draining the testis and its covers, causing circulatory reflux along the inner spermatic vein [ 1 ]. Varicocele results in progressive testicular lesions and, if untreated, can lead to testicular atrophy [ 2 ]. Varicocele is considered the most frequently identified cause of male infertility [ 3 ]. The mechanisms involved in varicocele formation are not well known and probably are multiple, differing from one patient to another.

Histological findings in equine testes one year after standing laparoscopic peritoneal flap hernioplasty

In order to know reproduction-related complications due to standing laparoscopic peritoneal flap hernioplasty, histological characteristics of the testicles from five stallions one year after surgery were compared with seven testicles from four healthy stallions. Moreover, the daily sperm output (DSO) was determined before (T0) and one year after surgery (T12). DSO did not show significant differences between T0 and T12. The diameter of the seminiferous tubules was significantly decreased in the samples from the hernioplasty group. The percentage of tubules with full spermatogenesis was smaller in the hernioplasty group, but the difference was not significant. It can be concluded that standing laparoscopic peritoneal flap hernioplasty produced mild histological changes in the testicular parenchyma, epididymis and pampiniform plexus after one year follow-up.

The investigation of correlation between semen analysis parameters and intraparenchymal testicular spectral Doppler indices in patients with clinical varicocele

OBJECTIVES

Our aim was to evaluate the effect of clinical varicocele on testicular microcirculation measured by spectral Doppler analysis and investigate the correlation between Doppler ultrasonographic findings and semen parameters.

METHODS

Fifty patients who received a diagnosis of clinical varicocele in the Urology Department of our university hospital were enrolled in this prospective study. Varicocele grades were determined according to sonographic parameters, and a scrotal vein with a diameter of 2.5 mm or greater on color Doppler ultrasonography was included in the study. Spectral Doppler measurements of testicular arteries (peak systolic [PSV]/end-diastolic velocity [EDV], resistivity index [RI], pulsatility index [PI]) were measured from capsular and intratesticular branches of testicular arteries. All the patients were also assessed by semen analysis.

RESULTS

Mean age was 29.08 ± 5.42 years (range, 18-45 years). Among the whole study population, 22 men had isolated left varicocele, and 28 had bilateral varicoceles. No statistically significant correlation was found between the Doppler parameters: RI, PI, and EDV, and semen analysis parameters: count, motility, volume, and morphology. On the other hand, both in unilateral and bilateral varicocele cases, PSV was found to be significantly correlated with sperm count (P < 0.05).

CONCLUSIONS

Spectral Doppler analysis can provide valuable information as a noninvasive method to assess the hemodynamic changes and testicular microcirculation status in cases of clinical varicocele. However, RI, PI, and EDV values of capsular and intraparenchymal branches of testicular arteries may not be used as indicators of semen parameter deterioration. Hopefully, PSV measurement may give more conclusive data to predict sperm count. In addition, the cutoff value for this index has to be determined for future studies.

Cadmium accumulation and metallothionein overexpression in internal spermatic vein of patients with varicocele

OBJECTIVES

To determine the possible molecular mechanism for the thickened wall in the internal spermatic vein (ISV) of patients with varicocele, we examined the cadmium (Cd) content and metallothionein (MT) expression in these diseased vessels. Previous studies have shown that Cd might play a role in the etiology of varicocele-associated infertility. MT, a metal-binding protein, protects against cell apoptosis during hypoxia.

METHODS

The study group consisted of 20 patients with grade 3 left varicocele. The control group consisted of 15 volunteers with left-sided indirect inguinal hernia. Through a left inguinal incision, a 1-cm section of the ISV was resected from each patient to measure the Cd and MT levels. The results were analyzed using Student's t test.

RESULTS

The Cd content in the ISV was 59.84 +/- 5.7 ng/g in the control group and 192.1 +/- 24.2 ng/g in the varicocele group. The relative intensity of the MT band was 40.52 +/- 3.74 in the control group and 78.26 +/- 5.61 in the varicocele group. MT expression was greater in the varicocele group than in the control group, and its deposition in the vascular endothelial layer was predominant using immunohistochemistry staining and confocal laser scanning.

CONCLUSIONS

The results of the present study have demonstrated a greater accumulation of Cd in the ISV of the varicocele group than in the control group. The high Cd content and hypoxic conditions would induce overexpression of MT in the diseased vessels to protect the vascular cells from apoptosis. This might be a mechanism for the thickened wall of the ISV in patients with varicocele.

Involved intrinsic apoptotic pathway of testicular tissues in varicocele-induced rats

INTRODUCTION

Increased testicular germ cell apoptosis has been reported in varicocele-induced rats. We studied intrinsic or extrinsic pathway of apoptosis by detecting Bcl-2, caspase-9, caspase-8, and activated caspase-3 expressions in the bilateral testes of experimental varicocele-induced rats.

MATERIALS AND METHODS

Experimental left varicocele (ELV) was created by partial ligation of left renal vein in a study group of 24 adult male Sprague-Dawley rats. The other 24 rats were as control group. Eight rats from each group were killed at 4, 8, and 12 weeks following varicocele creation. Testicular tissues of both groups were sampled for TUNEL assay and immunoblotting.

RESULTS

Increased apoptotic germ cell was found in the ipsilateral testis of varicocele group at 8 and 12 weeks after operation (P < 0.05). Increased activated caspase-3 expression in the contralateral (right) testis was noted at 12 weeks following varicocele creation (P < 0.05).

CONCLUSIONS

Our study demonstrates down-regulation of Bcl-2 expression and increased expressions of caspase-9 and activated caspase-3 in the ipsilateral testis of ELV rats at 8 and 12 weeks, indicating gradually increased testicular tissues apoptosis through the intrinsic pathway in varicocele-induced rats. Simultaneously, increased apoptosis in the contralateral testis was observed at 12 weeks (P < 0.05) following varicocele creation also.

Effects of hyperglycemia on sperm and testicular cells of Goto-Kakizaki and streptozotocin-treated rat models for diabetes

Diabetes mellitus is a degenerative disease that has deleterious effects on male reproductive function, possibly through an increase in oxidative stress. This study was conducted in order to clarify the mechanisms by which oxidative stress influences animal models for both type 1 (streptozotocin-treated rats, STZ) and type 2 (Goto-Kakizaki (GK) rats) diabetes. We determined the extent of lipid peroxidation, protein oxidation, lactate levels, adenine nucleotides, adenylate energy charge and the activity of glutathione peroxidase, glutathione reductase and lactate dehydrogenase, in isolated testicular cells of control and diabetic rats. We have also correlated these parameters with sperm count and motility. Sperm concentration and motility were decreased in STZ-treated rats. ATP levels were lower in rats treated with STZ for 3 months, in contrast to GK and rats treated with STZ for 1 month, suggesting an adaptative response. STZ-treated rats showed increased lipid peroxidation after 1 week and 3 months of treatment. Glutathione reductase (G-red) activity was found to be higher in GK rats. Glutathione peroxidase activity was lower in GK and rats treated with STZ for 1 month, which is in accordance with the proposal of functional recovery in these animals. We conclude that hyperglycemia has an adverse effect in sperm concentration and motility via changes in energy production and free radical management. Furthermore, both animal models, particularly GK rats and rats treated with STZ for 1 month, present some metabolic adaptations, increasing the efficiency of mitochondrial ATP production, in order to circumvent the deleterious effects promoted by the disease.

Color Doppler ultrasound investigation of varicocele

Varicocele, whose association with male infertility has been clearly documented in the literature, is a common finding in adolescents and adult men, being diagnosed in 20-40% of infertile patients. A correct and early diagnosis of this affliction is of great importance because, in most cases, a timely correction, usually performed using percutaneous sclerotherapy, leads to an improvement in semen quality. Currently, physical examination in a warm room is the mainstay of diagnosis, but this is affected by a low sensibility and specificity, especially in cases of low grade varicocele. Colour Doppler ultrasound (CDU) is a new, reliable and non-invasive diagnostic method for the evaluation of varicocele testes which allows the detection of even subclinical varicocele thanks to its capacity for measuring the size of the pampiniformis plexus and blood flow parameters of the spermatic veins. At present, there is a lack of completely standardised diagnostic criteria, but when this problem is solved, clinical examination and CDU will certainly become the "gold standard" in the investigation of varicocele.

The role of reactive oxygen species and apoptosis in the pathogenesis of varicocele in a rat model and efficiency of vitamin E treatment

We investigated role of reactive oxygen species (ROS) and apoptosis in the pathogenesis of infertility in experimental model of varicocele. The protective effect of vitamin E was also examined. Three groups of rats were constructed as the first group had sham operation, experimental varicoceles were established by partial ligation of the left renal vein in later two groups. Third group had received vitamin E. Production of ROS was determined by chemiluminescence assay (CL). The in situ end labelling technique was utilized to investigate apoptosis. Tissue vitamin E levels were measured by high performance liquid chromatography. The differences between luminol enhanced CL levels of groups were not statistically significant. However, the difference between CL levels of lucigenin probe in left testicles of sham and varicocele groups were statistically significant ( p = 0.0007). Similarly, the results of the third group receiving vitamin E significantly differed from the varicocele group ( p = 0.0025). The difference of apoptotic index was also statistically significant between sham and varicocele groups ( p = 0.0038). Although the values of apoptotic index detected in the vitamin E group were lower compared with the varicocele group, the difference was not significant. This study proposes that ROS production and apoptosis in the testicles were induced with experimental varicocele. Vitamin E had a protective role. An increased rate of apoptosis with experimental varicocele suggests a molecular alteration, which may involve ROS overproduction as the triggering mechanism. Consequently, this study indicates an association between varicocele and infertility at molecular level through stimulation of ROS and apoptosis.

Coenzyme Q10: another biochemical alteration linked to infertility in varicocele patients?

Previously we demonstrated that coenzyme Q10 (CoQ10) is present in human seminal fluid and shows a direct correlation with seminal parameters except in patients with varicocele (VAR). We have now evaluated CoQ10 distribution in VAR, versus control subjects, in order to discover metabolic abnormalities within this condition. We studied 32 patients with VAR (11 with oligoasthenozoospermia, 13 with asthenozoospermia, and 8 with normozoospermia), and, as controls, the following groups of subjects, matched with VAR patients according to seminal parameters: 16 patients with idiopathic oligozoospermia, 11 patients with isolated asthenozoospermia, and 14 normal fertile men. CoQ10 was assayed in total seminal fluid, plasma, or cell pellet by high-performance liquid chromatography (HPLC). We found a significantly higher proportion of CoQ10 in seminal plasma in VAR; cellular CoQ10 showed an inverse correlation with sperm concentration and motility in VAR, at variance with controls. As seminal plasma ubiquinone reflects an interchange between intracellular and extracellular compartments, the different distribution in VAR patients could represent a greater sensitivity to peroxidative damage and could suggest reduced utilization for energy, which in turn could cause a defective motility even in patients with a normal cell count. These data suggest a pathophysiological role of CoQ10 in seminal plasma and a possible molecular defect in VAR.

Torsion-induced injury in rat testes does not affect mitochondrial respiration or the accumulation of mitochondrial mutations

Male rats were subjected to 1 h testicular torsion of the spermatic cord or 1 h torsion followed by detorsion and recovery up to 4 weeks. The extent of tissue damage was evaluated by a testicular biopsy score count and mitochondrial function. Torsion for 1 h followed by detorsion induced significant morphological damage, which became more severe with longer periods of recovery. This morphological damage could not be correlated with mitochondrial damage as assessed by measuring the 4834 bp mitochondrial DNA 'common deletion' using a quantitative competitive polymerase chain reaction (PCR) assay. Mitochondrial respiratory chain activity, as measured by mitochondrial oxygen consumption using an oxygen electrode, did not vary between the treated animals and the controls. We conclude that the common mitochondrial DNA deletion and oxygen consumption are not good indicators of testicular damage induced by torsion.