α-Hemolysin promotes uropathogenic E. coli persistence in Bladder epithelial cells Via abrogating bacteria-harboring lysosome acidification

There is a growing consensus that a significant proportion of recurrent urinary tract infections are linked to the persistence of uropathogens within the urinary tract and their re-emergence upon the conclusion of antibiotic treatment. Studies in mice and human have revealed that uropathogenic Escherichia coli (UPEC) can persist in bladder epithelial cells (BECs) even after the apparent resolution of the infection. Here, we found that, following the entry of UPEC into RAB27b+ fusiform vesicles in BECs, some bacteria escaped into the cytoplasmic compartment via a mechanism involving hemolysin A (HlyA). However, these UPEC were immediately recaptured within LC3A/B+ autophagosomes that matured into LAMP1+ autolysosomes. Thereafter, HlyA+ UPEC-containing lysosomes failed to acidify, which is an essential step for bacterial elimination. This lack of acidification was related to the inability of bacteria-harboring compartments to recruit V-ATPase proton pumps, which was attributed to the defragmentation of cytosolic microtubules by HlyA. The persistence of UPEC within LAMP1+ compartments in BECs appears to be directly linked to HlyA. Thus, through intravesicular instillation of microtubule stabilizer, this host defense response can be co-opted to reduce intracellular bacterial burden following UTIs in the bladder potentially preventing recurrence.

Mast cell regranulation requires a metabolic switch involving mTORC1 and a glucose-6-phosphate transporter

Mast cells (MCs) are granulated cells implicated in inflammatory disorders because of their capacity to degranulate, releasing prestored proinflammatory mediators. As MCs have the unique capacity to reform granules following degranulation in vitro, their potential to regranulate in vivo is linked to their pathogenesis. It is not known what factors regulate regranulation, let alone if regranulation occurs in vivo. We report that mice can undergo multiple bouts of MC regranulation following successive anaphylactic reactions. mTORC1, a nutrient sensor that activates protein and lipid synthesis, is necessary for regranulation. mTORC1 activity is regulated by a glucose-6-phosphate transporter, Slc37a2, which increases intracellular glucose-6-phosphate and ATP during regranulation, two upstream signals of mTOR. Additionally, Slc37a2 concentrates extracellular metabolites within endosomes, which are trafficked into nascent granules. Thus, the metabolic switch associated with MC regranulation is mediated by the interactions of a cellular metabolic sensor and a transporter of extracellular metabolites into MC granules.

Lactobacillus crispatus Limits Bladder Uropathogenic E. coli Infection by Triggering a Host Type I Interferon Response

Many urinary tract infections (UTIs) are recurrent because uropathogens persist within the bladder epithelial cells (BECs) for extended periods between bouts of infection. Because persistent uropathogens are intracellular, they are often refractive to antibiotic treatment. The recent discovery of endogenous Lactobacillus spp. in the bladders of healthy humans raised the question of whether these endogenous bacteria directly or indirectly impact intracellular bacterial burden in the bladder. Here, we report that in contrast to healthy women, female patients experiencing recurrent UTIs have a bladder population of Lactobacilli that is markedly reduced. Exposing infected human BECs to L. crispatus in vitro markedly reduced the intracellular uropathogenic Escherichia coli (UPEC) load. The adherence of Lactobacilli to BECs was found to result in increased type I interferon (IFN) production, which in turn enhanced the expression of cathepsin D within lysosomes harboring UPECs. This lysosomal cathepsin D-mediated UPEC killing was diminished in germ-free mice and type I IFN receptor-deficient mice. Secreted metabolites of L. crispatus seemed to be responsible for the increased expression of type I IFN in human BECs. Intravesicular administration of Lactobacilli into UPEC-infected murine bladders markedly reduced their intracellular bacterial load suggesting that components of the endogenous microflora can have therapeutic effects against UTIs.

Prognostic factors in diffuse proliferative lupus nephritis

BACKGROUND

Patients with diffuse proliferative lupus nephritis (DPLN) can have variable clinical course. Identification of the predictors of outcome would help to improve the management. We have studied the prognostic significance of clinical, laboratory and histological parameters in patients with DPLN.

METHODS

Twenty nine patients diagnosed to be having DPLN seen between 1987 and 1991 were followed up for over 57 months. Parameters assessed for prognostic significance included serum creatinine, urine protein at the time of biopsy, blood pressure, type of immunosuppression, composite scores and individual components of activity index (AI) and chronicity index (CI). Kaplan-Meier survival curves were plotted and the results were compared using log rank test. Fishers' exact test was used to study the risk factors.

RESULTS

End stage renal failure developed in 7/29 (24.1%) patients; 7/19 (36.8%) who had hypertension and 7/16 (43.8%) who had nephrotic proteinuria developed renal failure, while none who had normal blood pressure or nonnephrotic proteinuria, developed renal failure (p < 0.01). Three patients had high activity index (> 12) and all three developed renal failure. Other parameters such as age, gender, serum creatinine, type of immunosuppression, CI and individual components of AI failed to predict the outcome (p > 0.05).

CONCLUSION

Hypertension, nephrotic proteinuria and high AI were predictive of progression to end stage renal failure in patients with diffuse proliferative lupus nephritis.

Treatment of diffuse proliferative lupus nephritis: an Indian experience

BACKGROUND

Immunosuppressive therapy has improved the prognosis in lupus nephritis. However, infectious complications may contribute to morbidity. There is also debate on the best form of therapy. We, therefore, compared the results of two different forms of therapy.

METHOD

Twenty-nine patients diagnosed to have diffuse proliferative lupus nephritis were followed up over 54 months. The treatment consisted of azathioprine (1.5 mg/kg/day) or pulse intravenous cyclophosphamide (500 mg/m2 body surface area monthly) along with prednisolone (2 mg/kg on alternate days).

RESULTS

Seventeen patients received azathioprine (group A) and 12 received cyclophosphamide (group B). The mean (SD) follow up in groups A and B were 54.35 (33.6) and 52 (35.8) months, respectively. Apart from the higher number of males in group B, both groups were comparable for age, presence of hypertension, renal function, 24-hour urinary protein excretion and composite scores for histological activity and chronicity indices (p > 0.05). The renal survival estimated by the Kaplan-Meier method was similar in both groups (p > 0.05). Four patients had renal failure requiring replacement therapy in group A and 3 in group B. Major infective episodes were more common in group B than in group A (p = 0.03).

CONCLUSION

Azathioprine was as effective as pulse intravenous cyclophosphamide in preserving renal functions up to 54 months. Major infective episodes were more common with pulse intravenous cyclophosphamide.