Dexamethasone improves therapeutic outcomes in a preclinical bacterial epididymitis mouse model

Regional modulation of toll-like receptor signaling pathway genes in acute epididymitis in mice

BACKGROUND

Region-specific immune environments in the epididymis influence the immune responses to uropathogenic Escherichia coli (UPEC) infection, a relevant cause of epididymitis in men. Toll-like receptors (TLRs) are essential to orchestrate immune responses against bacterial infections. The epididymis displays region-specific inflammatory responses to bacterial-derived TLR agonists, such as lipopolysaccharide (LPS; TLR4 agonist) and lipoteichoic acid (LTA; TLR2/TLR6 agonist), suggesting that TLR-associated signaling pathways could influence the magnitude of inflammatory responses in epididymitis.

OBJECTIVES

To investigate the expression and regulation of key genes associated with TLR4 and TLR2/TLR6 signaling pathways during epididymitis induced by UPEC, LPS, and LTA in mice.

MATERIAL AND METHODS

Epididymitis was induced in mice using UPEC, ultrapure LPS, or LTA, injected into the interstitial space of the initial segment or the lumen of the vas deferens close to the cauda epididymidis. Samples were harvested after 1, 5, and 10 days for UPEC-treated animals and 6 and 24 h for LPS-/LTA-treated animals. Ex vivo epididymitis was induced by incubating epididymal regions from naive mice with LPS or LTA. RT-qPCR and Western blot assays were conducted.

RESULTS

UPEC infection up-regulated Tlr2, Tlr4, and Tlr6 transcripts and their associated signaling molecules Cd14, Ticam1, and Traf6 in the cauda epididymidis but not in the initial segment. In these epididymal regions, LPS and LTA differentially modulated Tlr2, Tlr4, Tlr6, Cd14, Myd88, Ticam1, Traf3, and Traf6 expression levels. NFKB and AP1 activation was required for LPS- and LTA-induced up-regulation of TLR-associated signaling transcripts in the cauda epididymidis and initial segment, respectively.

CONCLUSION

The dynamic modulation of TLR4 and TLR2/TLR6 signaling pathways gene expression during epididymitis indicates bacterial-derived antigens elicit an increased tissue sensitivity to combat microbial infection in a spatial manner in the epididymis. Differential activation of TLR-associated signaling pathways may contribute to fine-tuning inflammatory responses along the epididymis.

New aspects of activin biology in epididymal function and immunopathology

The activins (A and B) and their binding protein, follistatin, play crucial roles in development, immunoregulation and inflammation throughout the body. In the male reproductive tract of the mouse, activin A and B production is largely confined to the initial segment and proximal caput of the epididymis and the efferent ducts, under normal conditions, with very low expression in the corpus, cauda and vas deferens. However, activin A protein is present throughout the epididymis and vas deferens and is largely associated with the epithelium and interstitial macrophages. Conversely, the activin-binding protein follistatin is produced in the distal epididymis, with very high expression in the vas deferens. Activin activity in the distal tract is inhibited by follistatin, and the activin-follistatin balance is important for regulating coiling of the duct during epididymal development. In further experiments, as described in this report, in situ hybridisation was used to localise activin A mRNA principally to cells in the periductal zone and interstitium in the efferent ducts and proximal caput. Activin B mRNA, on the other hand, was localised to periductal cells in the efferent ducts and proximal epididymis and, most notably, to epithelial cells in the initial segment. Activin A is implicated in the regulation of mononuclear phagocyte function and immune responses in the caput and stimulates the expression of the key immunoregulatory protein, indoleamine 2,3-dioxygenase in this region. Activin A production in the corpus and cauda increases dramatically during bacterial epididymitis in mice, promoting inflammation and fibrosis and causing damage to the epithelium and obstruction of the epididymal duct. Consequently, it appears that the activin-follistatin axis is crucial for maintaining normal epididymal structure and function, but disruption of this balance during inflammation has deleterious effects on male fertility. Follistatin has therapeutic potential in ameliorating the proinflammatory and profibrotic effects of activins.

Novel underlying genetic markers for asthenozoospermia due to abnormal spermatogenesis and reproductive organ inflammation

Asthenozoospermia, a male fertility disorder, has a complex and multifactorial etiology. Moreover, the effectiveness of different treatments for asthenozoospermia remains uncertain. Hence, by using bioinformatics techniques, the present study aimed to determine the underlying genetic markers and pathogenetic mechanisms associated with asthenozoospermia due to abnormal spermatogenesis and inflammation of the reproductive tract. GSE160749 dataset was downloaded from the Gene Expression Omnibus database, and the data were filtered to obtain 1336 differentially expressed genes (DEGs) associated with asthenozoospermia. These DEGs were intersected with the epithelial mesenchymal transition datasets to yield 61 candidate DEGs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed, and the results revealed that these candidate DEGs were significantly enriched in the enzyme-linked receptor pathway and the thyroid hormone pathway. A protein-protein interaction network was constructed to identify the key genes of asthenozoospermia. A total of five key genes were identified, among which SOX9 was significantly upregulated, while HSPA4, SMAD2, HIF1A and GSK3B were significantly downregulated. These findings were validated by conducting reverse transcription-quantitative PCR for clinical semen samples. To determine the underlying molecular mechanisms, a regulatory network of transcription factors and miRNA-mRNA interactions was predicted. The expression levels of HSPA4, SMAD2 and GSK3B were positively associated with several related etiological genes of asthenozoospermia. In total, five key genes were closely associated with the level and type of immune cells; higher levels of activated B cells and CD8 T cells were observed in asthenozoospermia. Thus, the findings of the present study may provide clues to determine the underlying novel diagnostic genetic markers and treatment strategies for asthenozoospermia.

Iron regulatory proteins 1 and 2 have opposing roles in regulating inflammation in bacterial orchitis

Acute bacterial orchitis (AO) is a prevalent cause of intrascrotal inflammation, often resulting in sub- or infertility. A frequent cause eliciting AO is uropathogenic Escherichia coli (UPEC), a gram negative pathovar, characterized by the expression of various iron acquisition systems to survive in a low-iron environment. On the host side, iron is tightly regulated by iron regulatory proteins 1 and 2 (IRP1 and -2) and these factors are reported to play a role in testicular and immune cell function; however, their precise role remains unclear. Here, we showed in a mouse model of UPEC-induced orchitis that the absence of IRP1 results in less testicular damage and a reduced immune response. Compared with infected wild-type (WT) mice, testes of UPEC-infected Irp1-/- mice showed impaired ERK signaling. Conversely, IRP2 deletion led to a stronger inflammatory response. Notably, differences in immune cell infiltrations were observed among the different genotypes. In contrast with WT and Irp2-/- mice, no increase in monocytes and neutrophils was detected in testes of Irp1-/- mice upon UPEC infection. Interestingly, in Irp1-/- UPEC-infected testes, we observed an increase in a subpopulation of macrophages (F4/80+CD206+) associated with antiinflammatory and wound-healing activities compared with WT. These findings suggest that IRP1 deletion may protect against UPEC-induced inflammation by modulating ERK signaling and dampening the immune response.

Gasdermin D in macrophages drives orchitis by regulating inflammation and antigen presentation processes

Inflammation in the testes induced by infection and autoimmunity contributes significantly to male infertility, a public health issue. Current therapies using antibiotics and broad-spectrum anti-inflammatory drugs are ineffective against non-bacterial orchitis and induce side effects. This highlights the need to explore the pathogenesis of orchitis and develop alternative therapeutic strategies. In this study, we demonstrated that Gasdermin D (GSDMD) was activated in the testes during uropathogenic Escherichia coli (UPEC)-induced acute orchitis, and that GSDMD in macrophages induced inflammation and affected spermatogenesis during acute and chronic orchitis. In testicular macrophages, GSDMD promoted inflammation and antigen presentation, thereby enhancing the T-cell response after orchitis. Furthermore, the pharmacological inhibition of GSDMD alleviated the symptoms of UPEC-induced acute orchitis. Collectively, these findings provide the first demonstration of GSDMD's role in driving orchitis and suggest that GSDMD may be a potential therapeutic target for treating orchitis.

The regional distribution of resident immune cells shapes distinct immunological environments along the murine epididymis

The epididymis functions as transition zone for post-testicular sperm maturation and storage and faces contrasting immunological challenges, i.e. tolerance towards spermatozoa vs. reactivity against pathogens. Thus, normal organ function and integrity relies heavily on a tightly controlled immune balance. Previous studies described inflammation-associated tissue damage solely in the distal regions (corpus, cauda), but not in the proximal regions (initial segment, caput). To understand the observed region-specific immunity along the epididymal duct, we have used an acute bacterial epididymitis mouse model and analyzed the disease progression. Whole transcriptome analysis using RNAseq 10 days post infection showed a pro-inflammatory environment within the cauda, while the caput exhibited only minor transcriptional changes. High-dimensional flow cytometry analyses revealed drastic changes in the immune cell composition upon infection with uropathogenic Escherichia coli. A massive influx of neutrophils and monocytes was observed exclusively in distal regions and was associated with bacterial appearance and tissue alterations. In order to clarify the reasons for the region-specific differences in the intensity of immune responses, we investigated the heterogeneity of resident immune cell populations under physiological conditions by scRNASeq analysis of extravascular CD45+ cells. Twelve distinct immune cell subsets were identified, displaying substantial differences in distribution along the epididymis as further assessed by flow cytometry and immunofluorescence staining. Macrophages constituted the majority of resident immune cells and were further separated in distinct subgroups based on their transcriptional profile, tissue location and monocyte-dependence. Crucially, the proximal and distal regions showed striking differences in their immunological landscapes. These findings indicate that resident immune cells are strategically positioned along the epididymal duct, potentially providing different immunological environments required for addressing the contrasting immunological challenges and thus, preserving tissue integrity and organ function.

Oral Lycopene Administration Attenuates Inflammation and Oxidative Stress by Regulating Plasma Lipids in Rats with Lipopolysaccharide-Induced Epididymitis

Purpose

Epididymitis histological alterations and related long-term reproductive issues cannot be cured by antibiotics alone. Few studies have been done on the effect of lycopene on epididymitis, despite the fact that it is an efficient antioxidant. The objective of this study was to assess the impact of lycopene on Lipopolysaccharide (LPS)-induced epididymis and lipid metabolism.

Methods

Thirty-one 260–290g rats were separated into the blank control group (n=10), the oil-control group (n=10), the single intraperitoneal injection of 5 mg/kg LPS (n=5), and the continuous intragastric of 5 mg/kg lycopene (n=6). The animals were euthanized after four weeks, and blood and the epididymis were removed for analysis.

Results

Lycopene significantly decreased IL-1α, IL-1β, TNF-α, MCP-1, IL-6 and lipid peroxidation product Malondialdehyde in serum and epididymis. It significantly increased the epididymis’s antioxidant enzyme and total antioxidant capacity. According to LC-MS plasma lipidomics, lycopene increased phosphatidylcholine, lysophosphatidylcholine, decreased phosphatidylethanolamine, triacylglycerol, and diacylglycerol levels, changed the composition of lipids, altered metabolic pathways, and these changes were related to the mechanism of anti-inflammatory and oxidative stress. 20 lipids, including PC (20:5e) and LPC (14:0), were identified through additional Spearman correlation analysis as being related to cytokines and oxidation indices. They served as possible lipid markers that may be utilized to gauge the severity of inflammation.

Conclusion

Lycopene has anti-inflammatory and antioxidant properties that improve histopathological and functional damage in LPS-induced epididymitis and is an alternate supplement for treating epididymitis. Lipidomics provide new perspectives on the possible mechanism of lycopene in protecting against LPS-induced epididymitis by integrating lipid metabolism and inflammation.

C-Type Natriuretic Peptide Plays an Anti-Inflammatory Role in Rat Epididymitis Induced by UPEC

Human epididymitis is mainly caused by retrograde urinary tract infection with uropathogenic Escherichia coli (UPEC). This disease is an important factor (accounting for 20-30%) causing male infertility. C-type natriuretic peptide (CNP), a protein composed of 22 amino acids, is proved to play an immunoregulatory role in respiratory and cardiovascular systems. CNP is expressed extremely high in the epididymis, but whether CNP plays the same role in acute epididymitis is unclear. At first, we established an acute caput epididymitis model in rats with UPEC and treated them with CNP to measure inflammatory damage. Then RNA-seq transcriptome technology was used to reveal potential signal pathways. Secondly, the turbidity and activity of UPEC were assessed using a microplate reader and the amount of UPEC by agar plates after incubation with CNP. Thirdly, macrophages in caput epididymis were tested by immunohistochemistry (IHC). Meanwhile, lipopolysaccharide (LPS) with or without CNP was used to stimulate the macrophage (RAW264.7) in vitro and to detect the expression level of pro-inflammatory factors. Finally, the macrophage (RAW264.7) was treated with CNP, 8-Br-cGMP [cyclic guanosinc monophosphate (cGMP) analog] and KT5823 [protein kinase G (PKG) inhibitor], and the expression level of nuclear factor-k-gene binding (NF-kB) signal pathway was examined. The results showed that the damage of epididymis induced by UPEC as well as the pro-inflammatory factors could be alleviated significantly with CNP treatment. CNP could inhibit the activity and numbers of bacteria in both in vivo and in vitro experiments. Moreover, CNP repressed the invasion, and the expression of pro-inflammatory factors (such as NF-kB, IL-1β, IL-6, TNF-α) in macrophages and its effect could be inhibited by KT5823. Therefore, we drew a conclusion from the above experiments that CNP alleviates the acute epididymitis injury induced by UPEC. On one hand, CNP could inhibit the growth of UPEC. On the other hand, CNP could decrease invasion and inflammatory reaction of macrophages; the mechanism was involved in inhibiting NF-kB signal pathway through the cGMP/PKG in macrophages. This research would open up the possibility of using CNP as a potential treatment for epididymitis.

Corticosterone Enhances the AMPK-Mediated Immunosuppressive Phenotype of Testicular Macrophages During Uropathogenic Escherichia coli Induced Orchitis

Testicular macrophages (TM) play a central role in maintaining testicular immune privilege and protecting spermatogenesis. Recent studies showed that their immunosuppressive properties are maintained by corticosterone in the testicular interstitial fluid, but the underlying molecular mechanisms are unknown. In this study, we treated mouse bone marrow-derived macrophages (BMDM) with corticosterone (50 ng/ml) and uncovered AMP-activated protein kinase (AMPK) activation as a critical event in M2 polarization at the phenotypic, metabolic, and cytokine production level. Primary TM exhibited remarkably similar metabolic and phenotypic features to corticosterone-treated BMDM, which were partially reversed by AMPK-inhibition. In a murine model of uropathogenic E. coli-elicited orchitis, intraperitoneal injection with corticosterone (0.1mg/day) increased the percentage of M2 TM in vivo, in a partially AMPK-dependent manner. This study integrates the influence of corticosterone on M2 macrophage metabolic pathways, phenotype, and function, and highlights a promising new avenue for the development of innovative therapeutics for orchitis patients.

Differential Immune Response to Infection and Acute Inflammation Along the Epididymis

The epididymis is a tubular structure connecting the vas deferens to the testis. This organ consists of three main regions—caput, corpus, and cauda—that face opposing immunological tasks. A means of combating invading pathogens is required in the distally located cauda, where there is a risk of ascending bacterial infections originating from the urethra. Meanwhile, immune tolerance is necessary at the caput, where spermatozoa with immunogenic neo-antigens originate from the testis. Consistently, when challenged with live bacteria or inflammatory stimuli, the cauda elicits a much stronger immune response and inflammatory-inflicted damage than the caput. At the cellular level, a role for diverse and strategically positioned mononuclear phagocytes is emerging. At the mechanistic level, differential expression of immunoprotective and immunomodulatory mediators has been detected between the three main regions of the epididymis. In this review, we summarize the current state of knowledge about region-specific immunological characteristics and unveil possible underlying mechanisms on cellular and molecular levels. Improved understanding of the different immunological microenvironments is the basis for an improved therapy and counseling of patients with epididymal infections.

Differential tissue-specific damage caused by bacterial epididymo-orchitis in the mouse

Ascending bacterial urinary tract infections can cause epididymo-orchitis. In the cauda epididymidis, this frequently leads to persistent tissue damage. Less coherent data is available concerning the functional consequences of epididymo-orchitis on testis and caput epididymidis. This in vivo study addresses the functional and spatial differences in responsiveness of murine epididymis and testis to infection with uropathogenic Escherichia coli (UPEC). Whole transcriptome analysis (WTA) was performed on testis, caput, corpus and cauda epididymidis of adult C57BL/6 J wildtype mice. Following UPEC-induced epididymo-orchitis in these mice, epididymal and testicular tissue damage was evaluated histologically and semi-quantitatively at 10 days and 31 days post-inoculation. Expression of inflammatory markers and candidate antimicrobial genes were analysed by RT-qPCR. WTA revealed distinct differences in gene signatures between caput and cauda epididymidis, particularly amonst immunity-related genes. Cellular and molecular signs of testicular inflammation and disruption of spermatogenesis were noticed at day 10, but recovery was observed by day 31. In contrast to the cauda, the caput epididymidis did not reveal any signs of gross morphological damage or presence of pro-inflammatory processes despite confirmed infection. In contrast to beta-defensins, known UPEC-associated antimicrobial peptides (AMP), like Lcn2, Camp and Lypd8, were inherently highly expressed or upregulated in the caput following infection, potentially allowing an early luminal protection from UPEC. At the time points investigated, the caput epididymidis was protected from any obvious infection/inflammation-derived tissue damage. Studies addressing earlier time-points will conclude whether in the caput epididymidis a pro-inflammatory response is indeed not essential for effective protection from UPEC.