Angiotensin II regulates testicular peritubular cell function via AT1 receptor: a specific situation in male infertility

Testicular immunity

The testis is a unique environment where immune responses are suppressed to allow the development of sperm that possess autoimmunogenic antigens. There are several contributors responsible for testicular immune privilege, including the blood-testis barrier, testicular immune cells, immunomodulation by Sertoli cells, and high levels of steroid hormones. Despite multiple mechanisms in place to regulate the testicular immune environment, pathogens that disrupt testicular immunity can lead to long-term effects such as infertility. If testicular immunity is disturbed, autoimmune reactions can also occur, leading to aberrant immune cell infiltration and subsequent attack of autoimmunogenic germ cells. Here we discuss cellular and molecular factors underlying testicular immunity and how testicular infection or autoimmunity compromise immune privilege. We also describe infections and autoimmune diseases that impact the testis. Further research into testicular immunity will reveal how male fertility is maintained and will help update therapeutic strategies for infertility and other testicular disorders.

Exploring the therapeutic effects of sulforaphane: an in-depth review on endoplasmic reticulum stress modulation across different disease contexts

The endoplasmic reticulum (ER) is an intracellular organelle that contributes to the folding of proteins and calcium homeostasis. Numerous elements can disrupt its function, leading to the accumulation of proteins that are unfolded or misfolded in the lumen of the ER, a condition that is known as ER stress. This phenomenon can trigger cell death through the activation of apoptosis and inflammation. Glucoraphanin (GRA) is the predominant glucosinolate found in cruciferous vegetables. Various mechanical and biochemical processes activate the enzyme myrosinase, leading to the hydrolysis of glucoraphanin into the bioactive compound sulforaphane. Sulforaphane is an organosulfur compound that belongs to the isothiocyanate group. It possesses a wide range of activities and has shown remarkable potential as an anti-inflammatory, antioxidant, antitumor, and anti-angiogenic substance. Additionally, sulforaphane is resistant to oxidation, has been demonstrated to have low toxicity, and is considered well-tolerable in individuals. These properties make it a valuable natural dietary supplement for research purposes. Sulforaphane has been demonstrated as a potential candidate drug molecule for managing a range of diseases, primarily because of its potent antioxidant, anti-inflammatory, and anti-apoptotic properties, which can be mediated by modulation of ER stress pathways. This review seeks to cover a wealth of data supporting the broad range of protective functions of sulforaphane, improving various diseases, such as cardiovascular, central nervous system, liver, eye, and reproductive diseases, as well as diabetes, cancer, gastroenteritis, and osteoarthritis, through the amelioration of ER stress in both in vivo and in vitro studies.

Identification of Catecholamine and Drug Target α2A-Adrenoceptor in Human Testis and Human Testicular Peritubular Cells

Background: Clonidine has been used in clinical medicine, e.g., to treat high blood pressure and other conditions. Animal studies have linked its use to impairments of male reproductive functions, and although only a few reports exist for the human species, such actions may exist in man as well. The underlying reasons and, specifically, possible actions of clonidine at the level of the testis are not known. Introduction: Clonidine is an agonist at the α2A-adrenoceptor (ADRA2A), which, as data bank mining indicated, is expressed by several cells of the human testis. The human testis and most of its cells are, however, not readily accessible to experimental testing. Cells from the peritubular wall compartment (human testicular peritubular cells; HTPCs) are the exception. Methods and Results: As shown by immunohistochemical/immunocytochemical and PCR techniques these cells express ADRA2A and retain expression upon isolation and culture. When tested over a concentration range (1-1000 µM) and 24 h, clonidine did not visibly affect HTPC morphology but significantly stimulated IL6 mRNA levels in a concentration-dependent manner. ELISA measurements of cell culture supernatants confirmed a stimulatory action of clonidine (10 µM) on secreted IL6. When examined in collagen gel contraction assays of HTPCs, clonidine (10 µM) exerted a slight relaxing action, while a proteomic study revealed that clonidine (10 µM) did not significantly change cellular protein abundance of HTPCs after 24 h (data available via ProteomeXchange with identifier PXD052220). Conclusion: Thus, ADRA2A-bearing cells in the human testis are targets for catecholamines and drugs such as clonidine. The results of this HTPCs-focused study only show the tip of the iceberg. It is likely that catecholamines/catecholaminergic drugs have the potential to interfere with human testicular functions.

Angiotensin-(1-7) plays an important role in regulating spermatogenesis in Trachemys scripta elegans under salinity stress

Elevation in water salinity can threaten the spermatogenesis and fertility of freshwater animals. The role of the renin-angiotensin system (RAS) in regulating spermatogenesis has attracted considerable attention. Our previous study found that red-eared sliders (Trachemys scripta elegans), could survive in 10 PSU water for over 1 year. To understand the chronic impact of salinity on testicular spermatogenesis and underlying mechanisms, male T. s. elegans were subjected to treatment with water of 5 PSU and 10 PSU for a year, and spermatogenesis and regulation of the RAS signal pathway was assessed. Results showed induced inflammation in the testes of T. s. elegans in the 10 PSU group, as evidenced by a decrease in the number of testicular germ cells from 1586 to 943. Compared with the control group, the levels of proinflammatory genes, including TNF-α, IL-12A and IL-6 were elevated 3.1, 0.3, and 1.4 times, respectively, in animals exposed to 10 PSU water. Testicular antiapoptotic processes of T. s. elegans might involve the vasoactive peptide angiotensin-(1-7) in the RAS, as its level was significantly increased from 220.2 ng ml-1 in controls to 419.2 ng ml-1 in the 10 PSU group. As expected, specific inhibitor (A-779) for the Ang-(1-7) acceptor effectively prevented the salinity-induced upregulation of genes encoding anti-inflammatory and antiapoptotic factors (TGF-β1, Bcl-6) in the testis of the 10 PSU animals, whereas it promoted the upregulation of proinflammatory and proapoptotic factors (TNF-α, IL-12A, IL-6, Bax and caspase-3). Our data indicated that Ang-(1-7) attenuates the effect of salinity on inflammation and apoptosis of the testis in T. s. elegans. A new perspective to prevent salinity-induced testis dysfunction is provided.

Exploration of multifaceted molecular mechanism of angiotensin-converting enzyme 2 (ACE2) in pathogenesis of various diseases

Angiotensin converting enzyme 2 (ACE2) is a homolog of ACE (a transmembrane bound dipeptidyl peptidase enzyme). ACE2 converts angiotensinogen to the heptapeptide angiotensin-(1-7). ACE2 and its product, angiotensin-(1-7), have counteracting effects against the adverse actions of other members of renin-angiotensin system (RAS). ACE2 and its principal product, angiotensin-(1-7), were considered an under recognized arm of the RAS. The COVID-19 pandemic brought to light this arm of RAS with special focus on ACE2. Membrane bound ACE2 serves as a receptor for SARS-CoV-2 viral entry through spike proteins. Apart from that, ACE2 is also involved in the pathogenesis of various other diseases like cardiovascular disease, cancer, respiratory diseases, neurodegenerative diseases and infertility. The present review focuses on the molecular mechanism of ACE2 in neurodegenerative diseases, cancer, cardiovascular disease, infertility and respiratory diseases, including SARS-CoV-2. This review summarizes unveiled roles of ACE2 in the pathogenesis of various diseases which further provides intriguing possibilities for the use of ACE2 activators and RAS modulating agents for various diseases.

High SARS-CoV-2 tropism and activation of immune cells in the testes of non-vaccinated deceased COVID-19 patients

BACKGROUND

Cellular entry of SARS-CoV-2 has been shown to rely on angiotensin-converting enzyme 2 (ACE2) receptors, whose expression in the testis is among the highest in the body. Additionally, the risk of mortality seems higher among male COVID-19 patients, and though much has been published since the first cases of COVID-19, there remain unanswered questions regarding SARS-CoV-2 impact on testes and potential consequences for reproductive health. We investigated testicular alterations in non-vaccinated deceased COVID-19-patients, the precise location of the virus, its replicative activity, and the immune, vascular, and molecular fluctuations involved in the pathogenesis.

RESULTS

We found that SARS-CoV-2 testicular tropism is higher than previously thought and that reliable viral detection in the testis requires sensitive nanosensors or RT-qPCR using a specific methodology. Through an in vitro experiment exposing VERO cells to testicular macerates, we observed viral content in all samples, and the subgenomic RNA's presence reinforced the replicative activity of SARS-CoV-2 in testes of the severe COVID-19 patients. The cellular structures and viral particles, observed by transmission electron microscopy, indicated that macrophages and spermatogonial cells are the main SARS-CoV-2 lodging sites, where new virions form inside the endoplasmic reticulum Golgi intermediate complex. Moreover, we showed infiltrative infected monocytes migrating into the testicular parenchyma. SARS-CoV-2 maintains its replicative and infective abilities long after the patient's infection. Further, we demonstrated high levels of angiotensin II and activated immune cells in the testes of deceased patients. The infected testes show thickening of the tunica propria, germ cell apoptosis, Sertoli cell barrier loss, evident hemorrhage, angiogenesis, Leydig cell inhibition, inflammation, and fibrosis.

CONCLUSIONS

Our findings indicate that high angiotensin II levels and activation of mast cells and macrophages may be critical for testicular pathogenesis. Importantly, our findings suggest that patients who become critically ill may exhibit severe alterations and harbor the active virus in the testes.

Profound Effects of Dexamethasone on the Immunological State, Synthesis and Secretion Capacity of Human Testicular Peritubular Cells

The functions of human testicular peritubular cells (HTPCs), forming a small compartment located between the seminiferous epithelium and the interstitial areas of the testis, are not fully known but go beyond intratesticular sperm transport and include immunological roles. The expression of the glucocorticoid receptor (GR) indicates that they may be regulated by glucocorticoids (GCs). Herein, we studied the consequences of the GC dexamethasone (Dex) in cultured HTPCs, which serves as a unique window into the human testis. We examined changes in cytokines, mainly by qPCR and ELISA. A holistic mass-spectrometry-based proteome analysis of cellular and secreted proteins was also performed. Dex, used in a therapeutic concentration, decreased the transcript level of proinflammatory cytokines, e.g., IL6, IL8 and MCP1. An siRNA-mediated knockdown of GR reduced the actions on IL6. Changes in IL6 were confirmed by ELISA measurements. Of note, Dex also lowered GR levels. The proteomic results revealed strong responses after 24 h (31 significantly altered cellular proteins) and more pronounced ones after 72 h of Dex exposure (30 less abundant and 42 more abundant cellular proteins). Dex also altered the composition of the secretome (33 proteins decreased, 13 increased) after 72 h. Among the regulated proteins were extracellular matrix (ECM) and basement membrane components (e.g., FBLN2, COL1A2 and COL3A1), as well as PTX3 and StAR. These results pinpoint novel, profound effects of Dex in HTPCs. If transferrable to the human testis, changes specifically in ECM and the immunological state of the testis may occur in men upon treatment with Dex for medical reasons.

The probable mechanism of reduced androgen level in COVID-19 patients

COVID-19, caused by the SARS-CoV-2, has challenged the health care systems of the world. Although the pulmonary complications of the infection have received extensive attention, addressing the other complications (e.g., changes in androgen levels) could further provide a more efficient understanding of the disease, which might aid in combating it. Since the association between androgens and the expression and activity of SARS-CoV-2 receptors has been proven and anti-androgen-based therapies have been considered in this regard, addressing various aspects of androgen level changes can be constructive. The present paper examines the possible mechanisms of changes in androgen levels by the virus. It seems that the infection of the gonads by the SARS-CoV-2 could reduce the androgen levels by affecting different cellular pathways.

Testicular adenosine acts as a pro-inflammatory molecule: role of testicular peritubular cells

Extracellular ATP has been described to be involved in inflammatory cytokine production by human testicular peritubular cells (HTPCs). The ectonucleotidases ENTPD1 and NT5E degrade ATP and have been reported in rodent testicular peritubular cells. We hypothesized that if a similar situation exists in human testis, ATP metabolites may contribute to cytokine production. Indeed, ENTPD1 and NT5E were found in situ and in vitro in HTPCs. Malachite green assays confirmed enzyme activities in HTPCs. Pharmacological inhibition of ENTPD1 (by POM-1) significantly reduced pro-inflammatory cytokines evoked by ATP treatment, suggesting that metabolites of ATP, including adenosine, are likely involved. We focused on adenosine and detected three of the four known adenosine receptors in HTPCs. One, A2B, was also found in situ in peritubular cells of human testicular sections. The A2B agonist BAY60-6583 significantly elevated levels of IL6 and CXCL8, a result also obtained with adenosine and its analogue NECA. Results of siRNA-mediated A2B down-regulation support a role of this receptor. In mouse peritubular cells, in contrast to HTPCs, all four of the known adenosine receptors were detected; when challenged with adenosine, cytokine expression levels significantly increased. Organotypic short-term testis cultures yielded comparable results and indicate an overall pro-inflammatory action of adenosine in the mouse testis. If transferable to the in vivo situation, our results may implicate that interference with the generation of ATP metabolites or interference with adenosine receptors could reduce inflammatory events in the testis. These novel insights may provide new avenues for treatment of sterile inflammation in male subfertility and infertility.

Angiotensin Receptor Blockers Are Not Just for Hypertension Anymore

Beyond blood pressure control, angiotensin receptor blockers reduce common injury mechanisms, decreasing excessive inflammation and protecting endothelial and mitochondrial function, insulin sensitivity, the coagulation cascade, immune responses, cerebrovascular flow, and cognition, properties useful to treat inflammatory, age-related, neurodegenerative, and metabolic disorders of many organs including brain and lung.

Regulation of Human Spermatogenesis

Human spermatogenesis (HS) is an intricate network of sequential processes responsible for the production of the male gamete, the spermatozoon. These processes take place in the seminiferous tubules (ST) of the testis, which are small tubular structures considered the functional units of the testes. Each human testicle contains approximately 600-1200 STs [1], and are capable of producing up to 275 million spermatozoa per day [2].

Filamin A Orchestrates Cytoskeletal Structure, Cell Migration and Stem Cell Characteristics in Human Seminoma TCam-2 Cells

Filamins are large dimeric F-actin cross-linking proteins, crucial for the mechanosensitive properties of a number of cell types. Due to their interaction with a variety of different proteins, they exert important regulatory functions. However, in the human testis the role of filamins has been insufficiently explored. Immunohistochemical staining of human testis samples identified filamin A (FLNA) in spermatogonia and peritubular myoid cells. Investigation of different testicular tumor samples indicated that seminoma also express FLNA. Moreover, mass spectrometric analyses identified FLNA as one of the most abundant proteins in human seminoma TCam-2 cells. We therefore focused on FLNA in TCam-2 cells, and identified by co-immunoprecipitation LAD1, RUVBL1 and DAZAP1, in addition to several cytoskeletal proteins, as interactors of FLNA. To study the role of FLNA in TCam-2 cells, we generated FLNA-deficient cells using the CRISPR/Cas9 system. Loss of FLNA causes an irregular arrangement of the actin cytoskeleton and mechanical instability, impaired adhesive properties and disturbed migratory behavior. Furthermore, transcriptional activity of typical stem cell factors is increased in the absence of FLNA. In summary, our data suggest that FLNA is crucially involved in balancing stem cell characteristics and invasive properties in human seminoma cells and possibly human testicular germ cells.

Effect of Venlafaxine, Pramipexole, and Valsartan on Spermatogenesis in Male Rats

The study's aim was to explore the effect of venlafaxine, valsartan, and pramipexole on spermatogenesis. It was hypothesized that these drugs may affect the male fertility because of their long-term use in treatment of depression, hypertension, and Parkinson's diseases. Male rats were given venlafaxine, valsartan, and pramipexole at low- and high-dose levels orally once daily for 10 weeks. Testosterone (25 mg/kg) was given as a standard via an intramuscular route once weekly. Rats were sacrificed after blood collection by cardiac puncture, and testes were removed. Sperm parameters were examined from spermatozoa of the cauda epididymis, and testes were treated for histopathological analysis. Results showed nonsignificant effect of venlafaxine on the sperm count, whereas a decreased sperm count was noted in all the treatment groups as compared to that of the control except valsartan at a low dose, which significantly (p < 0.001) raised the sperm count (96.26 ± 2.4) in reference with the control value (49.13 ± 2.3). Treatments had variable effects on total sperm motility and morphological parameters, but valsartan at a low dose showed maximum sperm motility (71.55 ± 0.7) among all. DNA integrity of spermatozoa remained intact in all groups. Luteinizing hormone and follicle-stimulating hormone levels decreased, and testosterone levels increased in all treatment groups as compared to control values, which indicate fertility. Histopathology revealed normal texture of testes with venlafaxine and valsartan, but testicular damage occurred with high-dose pramipexole. It is concluded that the use of venlafaxine, valsartan, and pramipexole at a low dose is devoid of any harmful effect on spermatogenesis, whereas pramipexole at a high dose adversely affect it.

Palmitic Acid Targets Human Testicular Peritubular Cells and Causes a Pro-Inflammatory Response

Palmitic acid (PA) is a major fatty acid, derived from diet and endogenous production, which is being linked to inflammation. While such actions of PA at the level of the testis remain difficult to examine, we reasoned that studies in human testicular cells may be instructive. Human testicular peritubular cells (HTPCs) can be isolated from men and cultured. They have contractile properties but also produce Interleukin 6 (IL6), express the inflammasome member NLRP3, and via glia cell line derived neurotrophic factor (GDNF), they contribute to the spermatogonial stem cell niche. We found that PA at 100 µM significantly increased the levels of IL6, while NLRP3 or the related Interleukin 1 beta (IL1beta) were not affected. The contractility marker calponin (CNN1) and the growth factor GDNF were likewise not affected. ELISA studies confirmed the stimulatory PA actions on IL6. Hence, PA derived from diet and/or endogenous sources may be able to foster a pro-inflammatory milieu in the testis. A possible link of these results to diet and high fat intake and obesity is indicated by the about 12-fold elevated testicular levels of IL6 in testes of obese rhesus monkeys (n = 3), fed with a Western Style diet. They had elevated 2–5-fold increased body fat and increased circulating triglyceride levels. Further consequences of PA and obesity for testicular functions remain to be evaluated.

The Glucocorticoid Receptor NR3C1 in Testicular Peritubular Cells is Developmentally Regulated and Linked to the Smooth Muscle-Like Cellular Phenotype

Whether glucocorticoids (GC) can directly affect human testicular functions is not well understood. A predominant site of GC receptor (GR; NR3C1) expression in the adult testis are peritubular smooth muscle-like cells, which express smooth muscle actin (ACTA2), contract and thereby are involved in sperm transport. In contrast to the adult, neither GR nor ACTA2, or elastin (ELN) were detected in the peritubular compartment before puberty in non-human primate testes. In isolated human testicular peritubular cells (HTPCs), activation of GR by dexamethasone (Dex) caused the translocation of GR to the nucleus and stimulated expression of ACTA2 and ELN, without affecting the expression of collagens. Cytoskeletal ACTA2-rearrangements were observed and were associated with an increased ability to contract. Our results indicate post-pubertal testicular roles of GC in the maintenance of the contractile, smooth muscle-like phenotype of peritubular cells.

Protective effects of tribulus terrestris extract and angiotensin blockers on testis steroidogenesis in copper overloaded rats

The rational of the current study was to assess whether Tribulus terrestris extract (TTE) could alleviate long-term copper (Cu) overload-induced testicular dysfunction compared to enalapril and losartan. Rats were administered either vehicle (control group, n = 10) or copper sulfate pentahydrate (CuSO₄·5H₂O, 200 mg/kg, p.o) for 90 days (n = 40). Cu-treated rats were randomized into four equal groups. One group was left untreated (Cu group) while the remaining three groups were daily co-treated with one of the following treatments along with CuSO4: TTE (10 mg/kg, p.o); enalapril (30 mg/kg, p.o); losartan (10 mg/kg, p.o). Excess Cu intake resulted in Cu overload coupled with a significant elevation in systolic blood pressure and serum angiotensin II levels along with a reduction in serum nitric oxide level. All concomitant treatments led to an alleviation of such deleterious effects. However, only losartan failed to ameliorate angiotensin II elevation. Additionally, all treatments protected the testes against Cu-overload-elicited zinc depletion and oxidative stress. Regarding reproductive function, the relative weights of testes, serum levels of testosterone and luteinizing hormone; the expression of steroidogenic genes; the protein levels of angiotensin II type 1 receptor and angiotensin converting enzyme 1, in addition to its activity, they were significantly reduced. Amongst all treatments, only TTE and E were able to revert these reproductive changes. In conclusion TTE and E were able to protect against Cu overload-induced impairment of testicular steroidogenesis. Thus, they might be considered as prophylactic drugs of choice against hypertension and testicular dysfunction to ameliorate Cu overload risk.

HDAC4 regulates vascular inflammation via activation of autophagy

Aims

Angiotensin II (Ang II) causes vascular inflammation, leading to vascular endothelial cell dysfunction, and is associated with the development of cardiovascular diseases. Therefore, interventions in inflammation may contribute to the reduction of cardiovascular diseases. Here, we aim to demonstrate that HDAC4, one of class IIa family histone de-acetylases (HDACs) members, promotes autophagy-dependent vascular inflammation.

Methods and results

By loss-of-function approaches, our study provides the first evidence that HDAC4 mediates Ang II-induced vascular inflammation in vitro and in vivo. In response to the Ang II, HDAC4 expression is up-regulated rapidly, with increased autophagic flux and inflammatory mediators in vascular endothelial cells (VECs). In turn, HDAC4 deficiency suppresses activation of autophagy, leading to reduced inflammation in Ang II-induced VECs. Consistently, using autophagy inhibitor or silencing LC3-II also alleviates vascular inflammation. Furthermore, HDAC4 regulates autophagy via facilitating transcription factor forkhead box O3a (FoxO3a) de-acetylation, thereby to increase its transcriptional activity. Loss of HDAC4 in VECs results in inhibition of FoxO3a de-acetylation to block its transcriptional activity, leading to downregulation of the downstream FoxO3a target, and hence reduces autophagy and vascular inflammation. FoxO3a silencing using siRNA approach significantly inhibits activation of autophagy. Finally, knockdown of HDAC4 in Ang II-infused mouse models ameliorates vascular inflammation, suggesting that inhibitor of HDAC4 may be potential therapeutics for vascular diseases associated with inflammation.

Conclusion

These results suggest that HDAC4-mediated FoxO3a acetylation regulates Ang II-induced autophagy activation, which in turn plays an essential role in causing vascular inflammation.

Peritubular cells of the human testis: prostaglandin E2 and more

BACKGROUND

Several layers of slender, smooth muscle-like, peritubular cells and extracellular matrix (ECM) form the peritubular compartment of the human testis. Peritubular cells are the least explored testicular cells.

MATERIALS AND METHODS

Human testicular peritubular cells (HTPCs) can be isolated from small testicular fragments of patients and studied in vitro. We have used this cellular model, in combination with human testicular samples, to examine how peritubular cells may contribute to male (in)fertility.

RESULTS

Human testicular peritubular cells (HTPCs) retain contractile abilities in vitro and secrete many proteins. Among them are factors, which serve intra-testicular roles, for example, glial cell line-derived neurotrophic factor (GDNF), thought to be important for the renewal of spermatogonial stem cells (SSCs). Studies in mutant mice indicated that peritubular cell-derived GDNF is crucial for lifelong spermatogenesis. Thus, peritubular cells are a functional part of the SSC niche. Peritubular cells of mice and men express androgen receptors (AR). In mouse peritubular cells, androgens enhanced GDNF production, but not in HTPCs. Rather, AR activation increased the levels of AR and smooth muscle proteins and thereby enhanced the smooth muscle-like phenotype. Following the lead of a proteomic analysis, which identified the key prostaglandin (PG)-synthesizing enzyme (PTGS1 = COX1), we found that HTPCs secrete PGE₂ . COX1, and PGE₂ receptors (EP1, 2, and 4) were identified in peritubular cells in situ, supporting in vivo relevance. In HTPCs, activation of EP1/4 increased GDNF and a smooth muscle protein. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID), which blocks PG synthesis. Added to HTPCs it reduced PGE₂ and GDNF production and lowered smooth muscle protein levels. If applicable to the in vivo situation, the results suggest that ibuprofen and possibly other NSAIDs may impair important peritubular cell functions and consequently testicular functions.

CONCLUSION

The few examples highlighted, together with others not mentioned here, indicate that HTPCs provide an experimental window into the human testis.

Characterization of a non-human primate model for the study of testicular peritubular cells-comparison with human testicular peritubular cells

STUDY QUESTION

Are monkey testicular peritubular cells (MKTPCs) from the common marmoset monkey (Callithrix jacchus) a suitable translational model for the study of human testicular peritubular cells (HTPCs)?

SUMMARY ANSWER

MKTPCs can be isolated and propagated in vitro, retain characteristic markers for testicular peritubular cells and their proteome strongly (correlation coefficient of 0.78) overlaps with the proteome of HTPCs.

WHAT IS KNOWN ALREADY

Smooth-muscle-like peritubular cells form the wall of seminiferous tubules, transport sperm, are immunologically active, secrete a plethora of factors and may contribute to the spermatogonial stem cell niche. Mechanistic studies are hampered by heterogeneity of human samples.

STUDY DESIGN, SIZE, DURATION

We established a culture method for MKTPCs and characterized these cells from six young adult animals (2-3 years). To examine whether they qualify as a translational model we also examined HTPCs from seven men and compared the proteomes of both groups.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We used explant cultures to obtain MKTPCs, which express smooth muscle markers (calponin (CNN1), smooth muscle actin (ACTA2)), lack FSH-receptors (FSHR) and LH-receptors (LHCGR), but possess androgen receptors (AR). MKTPCs can be passaged at least up to eight times, without discernable phenotypic changes. Mass-spectrometry-based analyses of the MKTPC and HTPC proteomes were performed.

MAIN RESULTS AND THE ROLE OF CHANCE

We established a method for isolation and cultivation of MKTPCs, and provide a comprehensive analysis of their protein repertoire. The results let us conclude that MKTPCs are suitable as a non-human primate model to study peritubular cell functions.

LARGE SCALE DATA

List of identified proteins in MKTPCs by liquid chromatography-tandem mass spectrometry is accessible at the ProteomeXchange (identifier PXD009394).

LIMITATIONS, REASON FOR CAUTION

This is an in vitro cellular non-human primate model used to provide a window into the role of these cells in the human testis.

WIDER IMPLICATIONS OF THE FINDINGS

Previous studies with HTPCs from patients revealed a degree of heterogeneity, possibly due to age, lifestyle and medical history of the individual human donors. We anticipate that the new translational model, derived from young healthy non-human primates, may allow us to circumvent these issues and may lead to a better understanding of the role of peritubular cells.

STUDY FUNDING AND COMPETION OF INTEREST(S)

This work was supported by grants from the Deutsche Forschungsgemeinschaft (MA 1080/27-1; AR 362/9-1; BE 2296/8-1). The authors declare no competing financial interests.

Human testicular peritubular cells, mast cells and testicular inflammation

In man, the wall of seminiferous tubules forms a testicular compartment, which contains several layers of smooth muscle-like, "myoid", peritubular cells and extracellular matrix. Its architecture and its cellular composition change in male infertility associated with impaired spermatogenesis. Increased deposits of extracellular matrix, changes in the smooth muscle-like phenotype of peritubular cells and accumulation of immune cells, especially mast cells, are among the striking alterations. Taken together, the changes indicate that inflammatory events take place in particular within this compartment. This short review summarises recent studies, which pinpoint possible mechanisms of the interplay between peritubular cells and mast cells, which may contribute to sterile inflammation and impairments of testicular function. These insights are based mainly on cellular studies, for which we used isolated human testicular peritubular cells (HTPCs), and on the examination of human testicular sections. Recent data on immunological properties of peritubular cells, unexpected roles of the extracellular matrix factor, biglycan, which is secreted by peritubular cells and functions of mast cell products (chymase, tryptase and ATP) are presented. We believe that the results may foster a better understanding of peritubular cells, their roles in the human testis and specifically their involvement in infertility.

New highlights on the health-improving effects of sulforaphane

In this paper, we review recent evidence about the beneficial effects of sulforaphane (SFN), which is the most studied member of isothiocyanates, on both in vivo and in vitro models of different diseases, mainly diabetes and cancer. The role of SFN on oxidative stress, inflammation, and metabolism is discussed, with emphasis on those nuclear factor E2-related factor 2 (Nrf2) pathway-mediated mechanisms. In the case of the anti-inflammatory effects of SFN, the point of convergence seems to be the downregulation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), with the consequent amelioration of other pathogenic processes such as hypertrophy and fibrosis. We emphasized that SFN shows opposite effects in normal and cancer cells at many levels; for instance, while in normal cells it has protective actions, in cancer cells it blocks the induction of factors related to the malignity of tumors, diminishes their development, and induces cell death. SFN is able to promote apoptosis in cancer cells by many mechanisms, the production of reactive oxygen species being one of the most relevant ones. Given its properties, SFN could be considered as a phytochemical at the forefront of natural medicine.

Ca2+ Signaling and IL-8 Secretion in Human Testicular Peritubular Cells Involve the Cation Channel TRPV2

Peritubular cells are part of the wall of seminiferous tubules in the human testis and their contractile abilities are important for sperm transport. In addition, they have immunological roles. A proteomic analysis of isolated human testicular peritubular cells (HTPCs) revealed expression of the transient receptor potential channel subfamily V member 2 (TRPV2). This cation channel is linked to mechano-sensation and to immunological processes and inflammation in other organs. We verified expression of TRPV2 in peritubular cells in human sections by immunohistochemistry. It was also found in other testicular cells, including Sertoli cells and interstitial cells. In cultured HTPCs, application of cannabidiol (CBD), a known TRPV2 agonist, acutely induced a transient increase in intracellular Ca²⁺ levels. These Ca²⁺ transients could be blocked both by ruthenium red, an unspecific Ca²⁺ channel blocker, and tranilast (TRA), an antagonist of TRPV2, and were also abolished when extracellular Ca²⁺ was removed. Taken together this indicates functional TRPV2 channels in peritubular cells. When applied for 24 to 48 h, CBD induced expression of proinflammatory factors. In particular, mRNA and secreted protein levels of the proinflammatory chemokine interleukin-8 (IL-8/CXCL8) were elevated. Via its known roles as a major mediator of the inflammatory response and as an angiogenic factor, this chemokine may play a role in testicular physiology and pathology.

Prostaglandin E2 (PGE2) is a testicular peritubular cell-derived factor involved in human testicular homeostasis

In man, blockage of prostaglandin (PG)-production e.g. by non-steroidal anti-inflammatory drug (NSAIDs) may have negative testicular side effects, implying beneficial actions of PGs in the testis. We examined human testicular samples and isolated human testicular peritubular cells (HTPCs) to explore sites of PG-synthesis and targets. HTPCs express cyclooxygenase 1 (COX1) and secrete PGE2. Receptors (EP1, 2, 4) were specifically identified in peritubular cells. In HTPCs PGE2 significantly increased mRNA levels of the contractility protein calponin, but did not induce contractions. PGE2, as well as EP1 and EP4 receptor agonists, significantly increased glia cell line derived neurotrophic factor (GDNF) mRNA and/or protein levels. Importantly, the NSAID ibuprofen reduced PGE2 and this action also lowered SMA and calponin mRNA levels and levels of secreted GDNF protein. The results reveal an unknown PGE2 system in the human testis, in involving peritubular cells, which may be prone to interference by NSAIDs.

NLRP3 in somatic non-immune cells of rodent and primate testes

NLRP3 is part of the NLRP3 inflammasome and a global sensor of cellular damage. It was recently discovered in rodent Sertoli cells. We investigated NLRP3 in mouse, human and non-human primate (marmoset and rhesus macaque) testes, employing immunohistochemistry. Sertoli cells of all species expressed NLRP3, and the expression preceded puberty. In addition, peritubular cells of the adult human testes expressed NLRP3. NLRP3 and associated genes (PYCARD, CASP1, IL1B) were also found in isolated human testicular peritubular cells and the mouse Sertoli cell line TM4. Male infertility due to impairments of spermatogenesis may be related to sterile inflammatory events. We observed that the expression of NLRP3 was altered in the testes of patients suffering from mixed atrophy syndrome, in which tubules with impairments of spermatogenesis showed prominent NLRP3 staining. In order to explore a possible role of NLRP3 in male infertility, associated with sterile testicular inflammation, we studied a mouse model of male infertility. These human aromatase-expressing transgenic mice (AROM+) develop testicular inflammation and impaired spermatogenesis during aging, and the present data show that this is associated with strikingly elevated Nlrp3 expression in the testes compared to WT controls. Interference by aromatase inhibitor treatment significantly reduced increased Nlrp3 levels. Thus, throughout species NLRP3 is expressed by somatic cells of the testis, which are involved in testicular immune surveillance. We conclude that NLRP3 may be a novel player in testicular immune regulation.

Insights into the role of androgen receptor in human testicular peritubular cells

Contractile smooth muscle-like peritubular cells build the wall of seminiferous tubules in men. They are crucial for sperm transport and complement the functions of Sertoli cells by secreting factors, including glial cell line-derived neurotrophic factor. Previous studies revealed that they also secrete the chemokine C-X-C motif chemokine ligand 12 (CXCL12), which has known roles in spermatogenesis. Peritubular cells express the androgen receptor (AR), which is retained in isolated human testicular peritubular cells. We aimed to explore AR-regulated functions in human testicular peritubular cells. Bearing in mind that infertile men often have high aromatase activity, which may lower intratesticular androgen concentrations, an animal model for male infertility was studied. These mice display an age-dependent loss in spermatogenesis due to high aromatase activity. Human testicular peritubular cells were exposed to dihydrotestosterone or the antiandrogen flutamide. We studied AR, smooth muscle cell markers, glial cell line-derived neurotrophic factor and 15 secreted factors previously identified, including CXCL12. We used qPCR, Western blotting, ELISA or selected reaction monitoring (SRM). In the animal model for male infertility, we employed qPCR and immunohistochemistry. Dihydrotestosterone increased AR and flutamide prevented these actions. The smooth muscle cell markers calponin and smooth muscle actin were likewise increased, while cell size or cellular proliferation was not changed. Dihydrotestosterone did not increase glial cell line-derived neurotrophic factor or CXCL12 secretion but increased levels of serine proteinase inhibitor (SERPIN) E1. The animal model for male infertility with high aromatase activity showed reduced numbers of AR-immunoreactive testicular peritubular cells, suggesting that altered androgen and/or oestrogen levels could influence AR-mediated responses in peritubular cells. Androgens act on human testicular peritubular cells to enhance AR levels, their contractile phenotype and to modulate the secretion of some secreted factors. This study suggests that some aspects of human peritubular cell functions are regulated by androgens.

Sulforaphane Prevents Angiotensin II-Induced Testicular Cell Death via Activation of NRF2

Although angiotensin II (Ang II) was reported to facilitate sperm motility and intratesticular sperm transport, recent findings shed light on the efficacy of Ang II in stimulating inflammatory events in testicular peritubular cells, effect of which may play a role in male infertility. It is still unknown whether Ang II can induce testicular apoptotic cell death, which may be a more direct action of Ang II in male infertility. Therefore, the present study aims to determine whether Ang II can induce testicular apoptotic cell death and whether this action can be prevented by sulforaphane (SFN) via activating nuclear factor (erythroid-derived 2)-like 2 (NRF2), the governor of antioxidant-redox signalling. Eight-week-old male C57BL/6J wild type (WT) and Nrf2 gene knockout mice were treated with Ang II, in the presence or absence of SFN. In WT mice, SFN activated testicular NRF2 expression and function, along with a marked attenuation in Ang II-induced testicular oxidative stress, inflammation, endoplasmic reticulum stress, and apoptotic cell death. Deletion of the Nrf2 gene led to a complete abolishment of these efficacies of SFN. The present study indicated that Ang II may result in testicular apoptotic cell death, which can be prevented by SFN via the activation of NRF2.

Sterile inflammation as a factor in human male infertility: Involvement of Toll like receptor 2, biglycan and peritubular cells

Changes in the wall of seminiferous tubules in men with impaired spermatogenesis imply sterile inflammation of the testis. We tested the hypothesis that the cells forming the wall of seminiferous tubules, human testicular peritubular cells (HTPCs), orchestrate inflammatory events and that Toll like receptors (TLRs) and danger signals from the extracellular matrix (ECM) of this wall are involved. In cultured HTPCs we detected TLRs, including TLR2. A TLR-2 ligand (PAM) augmented interleukin 6 (IL-6), monocyte chemo-attractant protein-1 (MCP-1) and pentraxin 3 (PTX3) in HTPCs. The ECM-derived proteoglycan biglycan (BGN) is secreted by HTPCs and may be a TLR2-ligand at HTPCs. In support, recombinant human BGN increased PTX3, MCP-1 and IL-6 in HTPCs. Variable endogenous BGN levels in HTPCs derived from different men and differences in BGN levels in the tubular wall in infertile men were observed. In testes of a systemic mouse model for male infertility, testicular sterile inflammation and elevated estradiol (E2) levels, BGN was also elevated. Hence we studied the role of E2 in HTPCs and observed that E2 elevated the levels of BGN. The anti-estrogen ICI 182,780 blocked this action. We conclude that TLR2 and BGN contribute to sterile inflammation and infertility in man.

Angiopoietin-like protein 2 expression is suppressed by angiotensin II via the angiotensin II type 1 receptor in rat cardiomyocytes

The present study aimed to determine the inhibitory effects of angiotensin II (AngII) on angiopoietin‑like protein 2 (Angptl2) in rat primary cardiomyocytes, and to investigate the potential association between angiotensin II type 1 receptor (AT1R) and these effects. Cardiomyocytes were isolated from 3-day-old Wistar rats, and were cultured and identified. Subsequently, the expression levels of Angptl2 were detected following incubation with various concentrations of AngII for various durations using western blotting, reverse transcription‑quantitative polymerase chain reaction, enzyme-linked immunosorbent assay and immunofluorescence. Finally, under the most appropriate conditions (100 nmol/l AngII, 24 h), the cardiomyocytes were divided into six groups: Normal, AngII, AngII + losartan, normal + losartan, AngII + PD123319 and normal + PD123319 groups, in order to investigate the possible function of AT1R in Angptl2 suppression. Losartan and PD123319 are antagonists of AT1R and angiotensin II type 2 receptor, respectively. The statistical significance of the results was analyzed using Student's t‑test or one‑way analysis of variance. The results demonstrated that Angptl2 expression was evidently suppressed (P<0.05) following incubation with 100 nmol/l AngII for 24 h. Conversely, the expression levels of Angptl2 were significantly increased in the AngII + losartan group compared with the AngII group (P<0.01). However, no significant difference was detected between the AngII + PD123319, normal + losartan or normal + PD123319 groups and the normal group. The present in vitro study indicated that AngII was able to suppress Angptl2 expression, whereas losartan was able to significantly reverse this decrease by inhibiting AT1R.

Spermatogenesis in humans and its affecting factors

Spermatogenesis is an extraordinary complex process. The differentiation of spermatogonia into spermatozoa requires the participation of several cell types, hormones, paracrine factors, genes and epigenetic regulators. Recent researches in animals and humans have furthered our understanding of the male gamete differentiation, and led to clinical tools for the better management of male infertility. There is still much to be learned about this intricate process. In this review, the critical steps of human spermatogenesis are discussed together with its main affecting factors.

Preparation and Biological Activity of the Monoclonal Antibody against the Second Extracellular Loop of the Angiotensin II Type 1 Receptor

The current study was to prepare a mouse-derived antibody against the angiotensin II type 1 receptor (AT1-mAb) based on monoclonal antibody technology, to provide a foundation for research on AT1-AA-positive diseases. Balb/C mice were actively immunized with the second extracellular loop of the angiotensin II type 1 receptor (AT₁R-ECII). Then, mouse spleen lymphocytes were fused with myeloma cells and monoclonal hybridomas that secreted AT1-mAb were generated and cultured, after which those in logarithmic-phase were injected into the abdominal cavity of mice to retrieve the ascites. Highly purified AT1-mAb was isolated from mouse ascites after injection with 1 × 10⁷ hybridomas. A greater amount of AT1-mAb was purified from mouse ascites compared to the cell supernatant of hybridomas. AT1-mAb purified from mouse ascites constricted the thoracic aorta of mice and increased the beat frequency of neonatal rat myocardial cells via the AT₁R, identical to the effects of AT1-AA extracted from patients' sera. Murine blood pressure increased after intravenous injection of AT1-mAb via the tail vein. High purity and good biological activity of AT1-mAb can be obtained from mouse ascites after intraperitoneal injection of monoclonal hybridomas that secrete AT1-mAb. These data provide a simple tool for studying AT1-AA-positive diseases.