Neutrophil Heparin-Binding Protein, Cytokines and Bacterial Virulence in the Pathogenesis of Severe Infection and Kidney Injury, and in Prediction for the Severity and Types of Diabetic Urinary Tract Infections

Diabetic patients have increased susceptibility to urinary tract infections (UTIs), and acute kidney injury (AKI) also occur more often in diabetic patients. The mechanism of increased prevalence and severity of UTIs in diabetic patients need further investigation. Uropathogenic E. Coli attachment to urothelial cells using fimbrial adhesins is the first step in development of UTIs. Among them, type 1 and P fimbriae are most associated with UTIs. Binding of type 1 or P fimbrial adhesins to the uroepithelial receptors are found to result in innate immunity (IL-6, IL-8 response) of uroepithelium in normal mice. The neutrophil-derived heparin-binding protein (HBP) is rapidly secreted upon activation of neutrophils. Recent studies have shown that HBP can be used as a biomarker for bacterial infections in vivo. In UTIs, the association between heparin-binding protein, cytokine response, bacterial virulence factor and the incidence of bacteremia or acute kidney injury in UTI in diabetic patients remains unknown. This study is divided into three parts: bacteria, animal model and human studies. In bacteria study, we will collect the pathogenic E. coli which are isolated from the included patients. We will detect their traditional virulence factors (fimH, papGII, hly, cnf1）and novel virulence factors (cjrABC-senB, sisA, sisB, fbpB, shiA, sivH, eco274）. And analyze the association of these virulence factors with the types (asymptomatic bacteriuria, lower UTI, upper UTI) and severity (bacteremia, sepsis, acute kidney injury) of UTIs. We will also analyze the relationship between the human urine or blood HBP, L-6, IL-8, IL-1B, NGAL(neutrophil gelatinase-associated lipocalin), KIM-1 and bacterial virulence factors to explore the roles of bacterial virulence factors in tissue inflammation and renal tubule injury. In animal studies, we investigate the incidence and severity of bladder and kidney infection in diabetic mice infected with E. coli with homologous type 1 or P fimbriae mutant or double mutant. The differences of neutrophil infiltration and activation (hepatic binding protein, NGAL) and cytokine response in diabetic and non-diabetic mice will be analyzed. And to detect the expression of Toll like receptor 4 (TLR4) in infected mice to investigate whether TLR4 signaling dysfunction is one of the reasons why it is easy to get urinary tract infection. In the human studies, we will explore whether blood and urine HBP concentrations are biomarkers that can distinguish asymptomatic bacteriuria, bladder infection or kidney infection and to study whether blood and urine HBP can be a good marker/predictor for sepsis, bacteremia, and acute kidney injury in patients with or without diabetes mellitus. We will compare HBP with other traditional biomarkers (IL-6, IL-8, IL-1B, NGAL, KIM-1) for analyses, and analyze the utilities of these biomarkers. The OPD patients who are older than 18 years of age with pyuria with or without UTI symptoms and those patients admitted to our ER for UTI management will be included and are classified as simple pyuria, asymptomatic bacteriuria, lower or upper UTIs, bacteremia and acute kidney injury group. The clinical data and urinary and blood levels of HBP, IL-6, IL-8, IL- NGAL, KIM-1, cystatin c, BUN, Cr will be analyzed.