Abstract
ObjectivesRecurrent urinary tract infections are associated with uropathogenic Escherichia coli (UPEC) ascending and infecting the urinary tract. Antibiotics provide only symptomatic relief, not prevent recurrence. Clinical evidence suggests that intravesical glycosaminoglycan therapy, such as hyaluronic acid (HA), helps reduce UTI recurrence. This has been investigated here using in vitro systems modelling the urogenital tract tissues.Methods RT4 bladder cells were preconditioned with high molecular weight HA (> 1500 kDa) at 2 mg mL−1 and challenged with UPEC to analyse barrier protection and bacterial adherence. Untreated and HA‐preconditioned VK2 E6/E7 vaginal cells were challenged with E. coli flagellin (50 ng mL−1) to mimic bacterial challenge, and media analysed for lipocalin‐2, human β‐defensin 2 and interleukin‐8 by ELISA. Experiments were repeated after siRNA knockdown of Toll‐like receptors 2, 4 and 5, and CD44 to investigate signalling.ResultsMicroscopic analyses showed reduced bacterial adherence and urothelial disruption with HA, suggesting that HA functions as a barrier protecting the epithelium from bacterial infection. Cells treated with HA and flagellin simultaneously produced more of the host antimicrobial peptide LCN2 and pro‐inflammatory IL‐8 (P < 0.05) compared to the no HA/flagellin challenges. Increased gene expression of DEFB4 (P < 0.05), but not the hBD2 peptide, was observed in the HA/flagellin‐challenged cells.ConclusionThese data suggest that exogenous HA has potential to protect the urogenital epithelia from UPEC infection via a two‐pronged approach that involves the physical enhancement of the epithelial barrier and augmentation of its innate immune response.
Highlights
Urinary tract infection (UTI) is one of the most common bacterial infections with an estimated 150 million cases reported annually.[1]
Confluent urothelial cell monolayers cultured in medium containing either HMW (1500–1800 kDa) hyaluronic acid (HA) (2 mg mLÀ1) or no HA were challenged with a flagellated uropathogenic E. coli (UPEC) strain, TPA4935J, isolated from the urine of a recurrent UTIs (rUTI) patient and modified to express GFP
Bladder instillations containing HA have been shown to reduce UTI episodes and pain[30,35,36] with in vivo studies suggesting that HA treatment is associated with reduced bacterial growth.[37]
Summary
Urinary tract infection (UTI) is one of the most common bacterial infections with an estimated 150 million cases reported annually.[1]. UTIs are caused when bacteria originating in the gastrointestinal tract colonise the vagina and peri-urethral area, and ascend to the bladder where they cause infection.[5] Such organisms include Staphylococcus, Proteus, Enterobacter, Klebsiella, Pseudomonas and Enterococcus the versatile pathogen Escherichia coli, known as uropathogenic E. coli (UPEC), accounts for > 70% of all infections.[6] Innate mechanisms are key in protecting the urinary tract from infection These include physical factors such as the flushing action of urine which, together with its acid pH and ionic composition, defend the urogenital tract against bacterial colonisation and adherence to the urothelium. Tolllike receptors (TLRs) located in the lower urogenital tissues respond to microbe-associated molecular patterns, flagellin, and trigger the release of host defence peptides as well as inflammatory molecules that function to clear potential UTIs.[7,8] The importance of the TLRs in defence of the urinary tract (UT) is emphasised by studies where individuals carrying the TLR5_C1174T (R392STOP) and TLR2_G2285A (R753Q) SNP genotypes link to an increased risk of infection.[9,10,11]
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