Damaged male germ cells induce epididymitis in mice

Spermatozoa-induced seminal vesiculitis in mice

BACKGROUND

Seminal vesiculitis is a common inflammation in the male genital tract. Etiologically, microbial infection and non-infectious factors can be responsible for seminal vesiculitis. The pathogenic triggers and mechanisms underlying non-infectious seminal vesiculitis remain unclear.

OBJECTIVES

To demonstrate that spermatozoa can induce seminal vesiculitis in mice, which could be attributable to spermatozoa-induced innate immune responses in seminal vesicular epithelial cells.

MATERIAL AND METHODS

Spermatozoa from epididymis were injected into seminal vesicles at the tail of the gland. Histopathology of seminal vesicles were examined by hematoxylin-eosin staining. Infiltration of leukocytes were identified by immunohistochemistry. Seminal vesicular epithelial cells were isolated from 5-week-old mice and cell types were detected by immunofluoresence. Western blot and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) were used to detect protein and gene expression levels.

RESULTS

In vivo, local injection of epididymal spermatozoa into seminal vesicles resulted in seminal vesiculitis characterized by tissue swelling and leukocyte infiltration. In vitro, spermatozoa induced the expression of pro-inflammatory cytokines and chemokines, including TNF-α, IL-6, CXCL10, and MCP1, and the activation of NF-κB in seminal vesicular epithelial cells.

DISCUSSION AND CONCLUSION

Spermatozoa may induce seminal vesiculitis through the activation of innate immune responses in seminal vesicular epithelial cells, which provide novel insights into the mechanisms underlying non-infectious seminal vesiculitis.

Single-cell RNA sequencing reveals the local cell landscape in mouse epididymal initial segment during aging

BACKGROUND

Morphological and functional alterations in aging reproductive organs result in decreased male fertility. The epididymis functions as the transition region for post-testicular sperm maturation. And we have previously demonstrated that the epididymal initial segment (IS), a region of the reproductive tract essential for sperm maturation and capacitation, undergoes considerable histological changes and chronic immune activation in mice during aging. However, the local aging-associated cellular and molecular changes in the aged epididymal IS are poorly understood.

RESULTS

We conducted single-cell RNA sequencing analysis on the epididymal IS of young (3-month-old) and old (21-month-old) mice. In total, 10,027 cells from the epididymal IS tissues of young and old mice were obtained and annotated. The cell composition, including the expansion of a principal cell subtype and Ms4a4b^HiMs4a6b^Hi T cells, changed with age. Aged principal cells displayed multiple functional gene expression changes associated with acrosome reaction and sperm maturation, suggesting an asynchronous process of sperm activation and maturation during epididymal transit. Meanwhile, aging-related altered pathways in immune cells, especially the "cell chemotaxis" in Cx3cr1^Hi epididymal dendritic cells (eDCs), were identified. The monocyte-specific expression of chemokine Ccl8 increased with age in eDCs. And the aged epididymal IS showed increased inflammatory cell infiltration and cytokine secretion. Furthermore, cell-cell communication analysis indicated that age increased inflammatory signaling in the epididymal IS.

CONCLUSION

Contrary to the general pattern of lower immune responses in the male proximal genital tract, we revealed an inflammaging status in mouse epididymal initial segment. These findings will allow future studies to enable the delay of male reproductive aging via immune regulation.

The NLRP3 inflammasome: molecular activation and regulation in spermatogenesis and male infertility; a systematic review

Background

Infertility related to varicocele, infections, metabolic dysfunctions, oxidative stress and environmental toxicants is also associated with inflammatory processes that ultimately lead to the activation of the inflammasome pathway (IP). IP is classically activated by DAMPs, MAMPs or LAMPs, which stand for Damage-, Microbe- or Lifestyle-Associated Molecular Patterns, respectively. The most important player in IP activation is the NLRP3 (NOD[Nuclear oligomerization domain]-, LRR[Leucine rich repeat]- and pyrin domain-containing protein 3) which functions as an intracellular sensor of D/M/L-AMPs resulting in activation of caspase-1, promotion of apoptosis, pyroptosis and generation of inflammatory cytokines. This review addresses the question of whether IP activation might be associated with male infertility situations.

Results & conclusions

We conducted a systematic review of articles published in the Google Scholar, and PubMed databases through October 2021. It turns out that inflammasome activation and its consequences including cytokine storms, apoptosis and pyroptosis could be associated with the reduced sperm count as well as the structural and functional sperm defects recorded in several situations associated with male infertility suggesting that anti-inflammatory therapeutic strategies could be possibly considered to restore male fertility in future research.

Activation of α-7 Nicotinic Acetylcholine Receptor Attenuates Cardiac Inflammation Through NLRP3/Caspase-1/IL-18 Pathway

Activation of α-7 nicotinic acetylcholine receptor (α7nAChR) receptor might induce cardiac inflammation, cardiac remodeling, and dysfunction. In this regard, this study aims to clarify the role and mechanism of α7nAChR in the process of cardiac inflammation and damage. Normal male C57BL/6J and NLRP3-knockout mice were used to evaluate the effect of PHA-543613, a selective agonist of α7nAChR, on cardiac inflammation and possible involvement of NLRP3/Caspase-1/IL-18 using western blotting and ELISA. Activation of α7nAChR using PHA-543613 (NE), at the doses of 0.5 mg/kg and 1 mg/kg, induced cardiac inflammation. In addition, both in vivo and in vitro studies showed higher expression of NLRP3 and higher activation of Caspase-1 and IL-18 after treating animals with NE. On the other hand, we did not observe any significant changes in inflammatory cytokines and cardiac inflammation after administration of NE in NLRP3-knockout mice. It could be concluded that blocking the NLRP3/Caspase-1/IL-18 pathway can simultaneously inhibit the inflammatory response mediated by α7nAChR and it would a novel target for inhibiting cardiac inflammation and remodeling.

Purinergic signaling in the male reproductive tract

Purinergic receptors are ubiquitously expressed throughout the body and they participate in the autocrine and paracrine regulation of cell function during normal physiological and pathophysiological conditions. Extracellular nucleotides activate several types of plasma membrane purinergic receptors that form three distinct families: P1 receptors are activated by adenosine, P2X receptors are activated by ATP, and P2Y receptors are activated by nucleotides including ATP, ADP, UTP, UDP, and UDP-glucose. These specific pharmacological fingerprints and the distinct intracellular signaling pathways they trigger govern a large variety of cellular responses in an organ-specific manner. As such, purinergic signaling regulates several physiological cell functions, including cell proliferation, differentiation and death, smooth muscle contraction, vasodilatation, and transepithelial transport of water, solute, and protons, as well as pathological pathways such as inflammation. While purinergic signaling was first discovered more than 90 years ago, we are just starting to understand how deleterious signals mediated through purinergic receptors may be involved in male infertility. A large fraction of male infertility remains unexplained illustrating our poor understanding of male reproductive health. Purinergic signaling plays a variety of physiological and pathophysiological roles in the male reproductive system, but our knowledge in this context remains limited. This review focuses on the distribution of purinergic receptors in the testis, epididymis, and vas deferens, and their role in the establishment and maintenance of male fertility.

Pattern recognition receptor-initiated innate immune responses in mouse prostatic epithelial cells‡

Three major pathogenic states of the prostate, including benign prostatic hyperplasia, prostate cancer, and prostatitis, are related to the local inflammation. However, the mechanisms underlying the initiation of prostate inflammation remain largely unknown. Given that the innate immune responses of the tissue-specific cells to microbial infection or autoantigens contribute to local inflammation, this study focused on pattern recognition receptor (PRR)-initiated innate immune responses in mouse prostatic epithelial cells (PECs). Primary mouse PECs abundantly expressed Toll-like receptor 3 (TLR3), TLR4, TLR5, melanoma differentiation-associated protein 5 (MDA5), and IFN-inducible protein 16 (p204 in mouse). These PRRs can be activated by their respective ligands: lipopolysaccharide (LPS) and flagellin of Gram-negative bacteria for TLR4 and TLR5, polyinosinic-polycytidylic acid (poly(I:C)) for TLR3 and MDA5, and herpes simplex virus DNA analog (HSV60) for p204. LPS and flagellin predominantly induced the expression of inflammatory cytokines, including tumor necrosis factor alpha (TNFA), interleukin 6 (IL6), chemokines monocyte chemoattractant protein-1 (MCP1), and C-X-C motif chemokine 10 (CXCL10). Poly(I:C) and HSV60 predominantly induced the expression of type 1 interferons (IFNA and IFNB) and antiviral proteins: Mx GTPase 1, 2',5'-oligoadenylate synthetase 1, and IFN-stimulated gene 15. The replication of mumps virus in PECs was inhibited by type 1 IFN signaling. These findings provide insights into the mechanisms underlying innate immune response in the prostate.