Necrosis Is the Dominant Cell Death Pathway in Uropathogenic Escherichia coli Elicited Epididymo-Orchitis and Is Responsible for Damage of Rat Testis

PLOS ONE, Dec 2019

Male infertility is a frequent medical condition, compromising approximately one in twenty men, with infections of the reproductive tract constituting a major etiological factor. Bacterial epididymo-orchitis results in acute inflammation most often caused by ascending canalicular infections from the urethra via the continuous male excurrent ductal system. Uropathogenic Escherichia coli (UPEC) represent a relevant pathogen in urogenital tract infections. To explore how bacteria can cause damage and cell loss and thus impair fertility, an in vivo epididymo-orchitis model was employed in rats by injecting UPEC strain CFT073 into the vas deference in close proximity to the epididymis. Seven days post infection bacteria were found predominantly in the testicular interstitial space. UPEC infection resulted in severe impairment of spermatogenesis by germ cell loss, damage of testicular somatic cells, a decrease in sperm numbers and a significant increase in TUNEL (+) cells. Activation of caspase-8 (extrinsic apoptotic pathway), caspase-3/−6 (intrinsic apoptotic pathway), caspase-1 (pyroptosis pathway) and the presence of 180 bp DNA fragments, all of which serve as indicators of the classical apoptotic pathway, were not observed in infected testis. Notably, electron microscopical examination revealed degenerative features of Sertoli cells (SC) in UPEC infected testis. Furthermore, the passive release of high mobility group protein B1 (HMGB1), as an indication of necrosis, was observed in vivo in infected testis. Thus, necrosis appears to be the dominant cell death pathway in UPEC infected testis. Substantial necrotic changes seen in Sertoli cells will contribute to impaired spermatogenesis by loss of function in supporting the dependent germ cells.

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Necrosis Is the Dominant Cell Death Pathway in Uropathogenic Escherichia coli Elicited Epididymo-Orchitis and Is Responsible for Damage of Rat Testis

et al. (2013) Necrosis Is the Dominant Cell Death Pathway in Uropathogenic Escherichia coli Elicited Epididymo-Orchitis and Is Responsible for Damage of Rat Testis. PLoS ONE 8(1): e52919. doi:10.1371/journal.pone.0052919 Necrosis Is the Dominant Cell Death Pathway in Uropathogenic Escherichia coli Elicited Epididymo- Orchitis and Is Responsible for Damage of Rat Testis Yongning Lu 0 Sudhanshu Bhushan 0 Svetlin Tchatalbachev 0 Marcelo Marconi 0 Martin Bergmann 0 Wolfgang Weidner 0 Trinad Chakraborty 0 Andreas Meinhardt 0 Stefan Schlatt, University Hospital of Mu nster, Germany 0 1 Department of Anatomy and Cell Biology, Unit of Reproductive Biology, Justus-Liebig-University Giessen , Giessen, Germany , 2 Department of Medical Microbiology, Justus-Liebig-University Giessen , Giessen, Germany , 3 Clinic and Policlinic of Urology, Pediatric Urology and Andrology, Justus-Liebig-University Giessen , Giessen, Germany , 4 Institute of Veterinary Anatomy, Histology, and Embryology, Justus-Liebig-University Giessen , Giessen , Germany Male infertility is a frequent medical condition, compromising approximately one in twenty men, with infections of the reproductive tract constituting a major etiological factor. Bacterial epididymo-orchitis results in acute inflammation most often caused by ascending canalicular infections from the urethra via the continuous male excurrent ductal system. Uropathogenic Escherichia coli (UPEC) represent a relevant pathogen in urogenital tract infections. To explore how bacteria can cause damage and cell loss and thus impair fertility, an in vivo epididymo-orchitis model was employed in rats by injecting UPEC strain CFT073 into the vas deference in close proximity to the epididymis. Seven days post infection bacteria were found predominantly in the testicular interstitial space. UPEC infection resulted in severe impairment of spermatogenesis by germ cell loss, damage of testicular somatic cells, a decrease in sperm numbers and a significant increase in TUNEL (+) cells. Activation of caspase-8 (extrinsic apoptotic pathway), caspase-3/26 (intrinsic apoptotic pathway), caspase-1 (pyroptosis pathway) and the presence of 180 bp DNA fragments, all of which serve as indicators of the classical apoptotic pathway, were not observed in infected testis. Notably, electron microscopical examination revealed degenerative features of Sertoli cells (SC) in UPEC infected testis. Furthermore, the passive release of high mobility group protein B1 (HMGB1), as an indication of necrosis, was observed in vivo in infected testis. Thus, necrosis appears to be the dominant cell death pathway in UPEC infected testis. Substantial necrotic changes seen in Sertoli cells will contribute to impaired spermatogenesis by loss of function in supporting the dependent germ cells. - Funding: This study was supported by grants from the Deutsche Forschungsgemeinschaft (KFO 181/2) to AM and TC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. The mammalian testis is essentially composed of two main compartments, ie. the interstitial space with the androgenproducing Leydig cells and leukocytes and the seminiferous tubules containing the developing germ cells in close physical association with the columnar Sertoli cells. In the interstitial space, testicular macrophages act as a first line of defense [1,2], whilst in the seminiferous epithelium the Sertoli cells, beside their role in supporting spermatogenesis, are undoubtedly of considerable importance in the control of immune response against pathogens arising from the ductal system. The recent discovery of microbial pattern recognition receptors such as Toll-like receptor (TLR) on Sertoli cells together with their ability to produce inflammatory mediators, places them in a central position to orchestrate protection from ascending canalicular microbial infection [35]. In turn many of the negative effects of infection/inflammation on spermatogenesis may be attributed to impaired Sertoli cell function with subsequent disruptive effects on germ cell development and survival [6,7]. Given the predominant occurrence of uropathogenic E. coli (UPEC) with urinary tract infections, it is not surprising that E. coli (apart from other sexually transmitted microbes) is the most frequently isolated pathogen from urine and semen samples of patients with prostatitis and epididymo-orchitis [810]. Direct characterization and analysis of bacterial traits or virulence genes such as alpha-hemolysin (HlyA) confirmed the relevance of uropathogenic E. coli (UPEC) in infectious male infertility and subfertility which overall ranks first amongst the known reasons for male factor infertility preceded only by idiopathic causes [1113]. In men, bacterial epididymo-orchitis is treated with antibiotic and antiphlogistic pharmacotherapy. Of note, (...truncated)


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Yongning Lu, Sudhanshu Bhushan, Svetlin Tchatalbachev, Marcelo Marconi, Martin Bergmann, Wolfgang Weidner, Trinad Chakraborty, Andreas Meinhardt. Necrosis Is the Dominant Cell Death Pathway in Uropathogenic Escherichia coli Elicited Epididymo-Orchitis and Is Responsible for Damage of Rat Testis, PLOS ONE, 2013, 1, DOI: 10.1371/journal.pone.0052919