Molecular mechanisms and immunomodulatory approaches in acute cystitis

Abstract: hand in the fight against resistant microbes. This thesis discusses the feasibility and potential of specific immunotherapy in treating acute bacterial infections and chronic sequels. The infection model is acute cystitis; the most common form of urinary tract infection, affecting millions of patients annually. Susceptible patients develop the characteristic clinical manifestation of dysuria, urgency and frequency of micturition. Antibiotics are used to treat the infection but increasingly, such therapies are becoming insufficient. Here we identify acute cystitis as an Interleukin (IL)-1β driven hyper-inflammatory disease and identify ASC and NLRP3 as genetic determinants of acute cystitis severity. IL-1β hyper-activation was attributed to non-canonical processing of pro-IL-1β by the matrix metalloproteinase (MMP)-7. This alternative mechanism was controlled by transcriptional de-repression of MMP7 by ASC in complex with NLRP-3. In addition, we show that the pain response that accompanies acute cystitis is driven by the neuropeptide Substance P and its Neurokinin-1 receptor (NK1R); also controlled by ASC and NLRP3 in infected nerve- and bladder cells. These findings suggest a molecular basis of acute cystitis pathogenesis and genetic tools to distinguish susceptible from resistant hosts. Evidence that immunotherapy might be efficient was obtained by inhibiting each of these targets. Using an IL-1 receptor antagonist (IL-1RA), IL-1 hyper-activation was inhibited and tissue pathology was reversed. Furthermore, the bacterial clearance was accelerated and the effect was shown to be comparable to antibiotic treatment in the treated mice. Using specific inhibitors of MMP7 or NK1R, similar treatment efficacy was acheived in highly susceptible Asc-/- or Nlrp3-/- mice. The results exemplify three treatment approaches, targeting hyper-inflammation in acute cystitis. IL-1RA was further tested for effects against antibiotic resistant strains and found to be effective. Patients with acute cystitis may experience recurrent infections and may develop into chronic sequels. Patients diagnosed with bladder pain syndrome were included in a prospective study to investigate the clinical potential of IL-1RA based therapy. Treated patients showed a marked reduction in symptoms and an increased quality of life. Symptom relief was accompanied by a reduction in urine Substance P levels and the expression of inflammatory genes was inhibited. The studies present a molecular context for acute cystitis and bladder pain and identify potential therapeutic targets in the host.