Ribonuclease 7 Shields the Kidney and Bladder from Invasive Uropathogenic Escherichia coli Infection

Abstract

BackgroundEvidence suggests that antimicrobial peptides, components of the innate immune response, protect the kidneys and bladder from bacterial challenge. We previously identified ribonuclease 7 (RNase 7) as a human antimicrobial peptide that has bactericidal activity against uropathogenic Escherichia coli (UPEC). Functional studies assessing RNase 7’s contributions to urinary tract defense are limited.MethodsTo investigate RNase 7’s role in preventing urinary tract infection (UTI), we quantified urinary RNase 7 concentrations in 29 girls and adolescents with a UTI history and 29 healthy female human controls. To assess RNase 7’s antimicrobial activity in vitro in human urothelial cells, we used siRNA to silence urothelial RNase 7 production and retroviral constructs to stably overexpress RNase 7; we then evaluated UPEC’s ability to bind and invade these cells. For RNase 7 in vivo studies, we developed humanized RNase 7 transgenic mice, subjected them to experimental UTI, and enumerated UPEC burden in the urine, bladder, and kidneys.ResultsCompared with controls, study participants with a UTI history had 1.5-fold lower urinary RNase 7 concentrations. When RNase 7 was silenced in vitro, the percentage of UPEC binding or invading human urothelial cells increased; when cells overexpressed RNase 7, UPEC attachment and invasion decreased. In the transgenic mice, we detected RNase 7 expression in the kidney’s intercalated cells and bladder urothelium. RNase 7 humanized mice exhibited marked protection from UPEC.ConclusionsThese findings provide evidence that RNase 7 has a role in kidney and bladder host defense against UPEC and establish a foundation for investigating RNase 7 as a UTI prognostic marker or nonantibiotic-based therapy.

Vaginal estrogen therapy is associated with increased Lactobacillus in the urine of postmenopausal women with overactive bladder symptoms

“…12 Although urinary AMP activity has been assessed in several urinary pathologies, 9,12e14 no studies have assessed the role of estrogen in modulating urinary AMP activity as a therapeutic option for women with OAB. Given that estrogen promotes epithelial differentiation, which is associated with greater AMP expression and activity, estrogen likely regulates urinary AMPs to optimize urobiome equilibrium 9,14,15 and impact the severity of OAB.…”

The Responses of the Ribonuclease A Superfamily to Urinary Tract Infection

“…However, it is important that similar structure-function tests be undertaken in the context of eukaryotic cells, which serve as the natural source of RNase A Superfamily members. Recently, we demonstrated that human urothelial cells can be genetically modified to over-express RNase 7, which confers antimicrobial activity toward UPEC (46). This type of experimental approach affords the opportunity to test the relationship between RNase 7 structural elements and antimicrobial function in the context of its cellular source.…”

“…RNase 7 is secreted into the urine and urinary concentrations increase with UTI to prevent infection (36, 45). Females and adolescent girls with recurrent UTI have suppressed urinary RNase 7 levels compared to controls without UTI (46). When human urine is incubated with RNase 7 neutralizing antibodies and inoculated with UPEC in vitro , bacterial growth significantly increases (36, 47).…”

“…RNase 7 expression in these mice did not impact urothelial histology, endogenous innate immune profiles, or the diversity of the gastrointestinal microbiome. When subjected to UTI in vivo , these mice were significantly protected from UPEC, suggesting that RNase 7 could be a therapeutic target for protection against UTI (46).…”

The Antimicrobial and Immunomodulatory Function of RNase 7 in Skin

“…Gene expression analyses revealed expression in various tissues such as heart, liver, kidney, pharynx, and tonsil (12, 13). In addition, the group of Spencer et al identified a major role of RNase 7 in kidney and bladder host defense (14, 15).…”