D-Mannose reduces cellular senescence and NLRP3/GasderminD/IL-1ß-driven pyroptotic uroepithelial cell shedding in the murine bladder.

Aging is a risk factor for disease via increased susceptibility to infection, decreased ability to maintain homeostasis, inefficiency in combating stress, and decreased regenerative capacity. Multiple diseases, including urinary tract infection (UTI), are more prevalent with age; however, the mechanisms underlying the impact of aging on the urinary tract mucosa and the correlation between aging and disease remain poorly understood. Here, we show that, relative to young (8-12 weeks) mice, the urothelium of aged (18-24 months) female mice accumulates large lysosomes with reduced acid phosphatase activity and decreased overall autophagic flux in the aged urothelium, indicative of compromised cellular homeostasis. Aged bladders also exhibit basal accumulation of reactive oxygen species (ROS) and a dampened redox response, implying heightened oxidative stress. Furthermore, we identify a canonical senescence-associated secretory phenotype (SASP) in the aged urothelium, along with continuous NLRP3-inflammasome- and Gasdermin-D-dependent pyroptotic cell death. Consequently, aged mice chronically exfoliate urothelial cells, further exacerbating age-related urothelial dysfunction. Upon infection with uropathogenic E. coli, aged mice harbor increased bacterial reservoirs and are more prone to spontaneous recurrent UTI. Finally, we discover that treatment with D-mannose, a natural bioactive monosaccharide, rescues autophagy flux, reverses the SASP, and mitigates ROS and NLRP3/Gasdermin/interleukin (IL)-1ß-driven pyroptotic epithelial cell shedding in aged mice. Collectively, our results demonstrate that normal aging affects bladder physiology, with aging alone increasing baseline cellular stress and susceptibility to infection, and suggest that mannose supplementation could serve as a senotherapeutic to counter age-associated urothelial dysfunction.

Supraphysiologic Vaginal Estrogen Therapy in Aged Mice Mitigates Age-Associated Bladder Inflammatory Response to Urinary Tract Infections.

IMPORTANCE: Bladder diseases characterized by chronic inflammation are highly prevalent in older women, as are recurrent urinary tract infections (rUTIs). Recurrent urinary tract infections lead to chronic inflammation of the bladder mucosa and cause lower urinary tract symptoms that persist even after the infection is cleared. Vaginal estrogen therapy (VET) has long been used for the treatment of rUTIs; however, its mechanism of action remains unclear. OBJECTIVES: The objective of this study was to examine the mechanism(s) by which VET affects bladder inflammation and response to rUTIs. STUDY DESIGN: Here, we induced surgical menopause in aged (18 months old) mice followed by VET. Mice were then infected with uropathogenic Escherichia coli , and course of infection was investigated. Inflammatory cytokine response was assessed before and during infection using enzyme-linked immunosorbent assay. RNA sequencing analysis was used to compare the inflammatory status of the young versus aged bladder and principal changes confirmed via quantitative reverse transcriptase-polymerase chain reaction to determine the effects of VET on bladder inflammation. Impact on age-associated bladder tertiary lymphoid tissue formation was evaluated histologically. RESULTS: In the ovariectomized aged model, VET not only mitigated uterine atrophy but was also associated with reduced rUTIs, number of bacterial reservoirs, dampened immune response, and promotion of terminal differentiation of urothelial cells. Bladder tertiary lymphoid tissue lesions were also reduced with VET, with an associated decrease in signals important for bladder tertiary lymphoid tissue formation. Finally, we determined that VET reverses age-associated upregulation of inflammatory genes and pathways. CONCLUSIONS: Our data suggest that VET is effective by reducing age-associated hyperinflammatory conditions in bladder mucosa and in enhancing the host response to infection.