Nitrofurantoin, phenazopyridine, and the superoxide-response regulon soxRS of Escherichia coli

Comparison of treatments for preventing lower urinary tract symptoms after BCG immunotherapy of bladder tumors : a systematic review and network meta-analysis

BACKGROUND

Bacillus Calmette-Guerin (BCG) immunotherapy is the standard adjuvant treatment for high-risk, non-muscle invasive bladder cancer (NMIBC). However, BCG immunotherapy is commonly accompanied by significant lower urinary tract symptoms (LUTS) including symptoms such as urinary urgency, frequency, dysuria and pelvic pain. These symptoms can undermine treatment adherence and clinical outcomes. In this study, the treatments for preventing LUTS after BCG instillations were compared through a systemic review and network meta-analysis (NMA).

METHODS

Eligible studies were obtained from the PubMed, Web of Science, Embase and Cochrane Library databases. We also searched the references of the included studies. Our protocol followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) checklist. We performed NMA using Review Manager 5.3 and STATA MP 18.0.

RESULT

The analysis included 6 studies with 556 participants. The results of the NMA revealed that celecoxib and prulifloxacin effectivelty reduce the incidence of LUTS including frequency, urgency and dysuria. Phenazopyridine showed the best performance in improving pelvic pain.

CONCLUSION

The NMA indicated that medications such as celecoxib, prulifloxacin and phenazopyridine are effective in reducing the incidence of LUTS after BCG immunotherapy of bladder tumors.

Ascorbate and Antibiotics, at Concentrations Attainable in Urine, Can Inhibit the Growth of Resistant Strains of Escherichia coli Cultured in Synthetic Human Urine

There are conflicting reports on the antibacterial activity of ascorbate; all at concentrations much higher than the typical in human plasma, but that can be reached in urine. The effect of 10 mM ascorbate (in itself not inhibitory) along with antibiotics, was tested both in Mueller-Hinton broth (MHb) and in synthetic human urine (SHU), against resistant isolates of Escherichia coli from lower urinary infections. The activity of nitrofurantoin and sulfamethoxazole was higher in SHU than in MHb; minimal inhibitory concentrations (MICs) in SHU with ascorbate were below typical urinary concentrations. For other antibiotics, MICs were the same in MHb vs. SHU, with no effect of ascorbate in MHb; but in SHU with ascorbate, MICs of ciprofloxacin and gentamicin also went below reported urinary concentrations, with a lesser effect with norfloxacin and trimethoprim, and none with ampicillin. The effect of ascorbate was independent of oxygen and not related to the susceptibility of each strain to oxidative stress. Ascorbate oxidizes during incubation in SHU, and bacterial growth partially prevented oxidation. These results suggest that 10 mM ascorbate can enhance the inhibitory activity of antibiotics upon resistant strains in urine. Clinical experimentation with ascorbate-antibiotic combinations against urinary infections caused by resistant bacteria is warranted.

Inhibition of TRPM8 by the urinary tract analgesic drug phenazopyridine

BACKGROUND

and purpose: Phenazopyridine (PAP) is an over-the-counter drug widely used to provide symptomatic relief of bladder pain in conditions such as cystitis or bladder pain syndrome (BPS). Whereas the analgesic effect of PAP has been attributed to a local effect on the mucosa of the lower urinary tract (LUT), the molecular targets of PAP remain unknown. We investigated the effect of PAP on pain-related Transient Receptor Potential (TRP) channels expressed in sensory neurons that innervate the bladder wall.

EXPERIMENTAL APPROACH

The effects of PAP on the relevant TRP channels (TRPV1, TRPA1, TRPM8, TRPM3) expressed in HEK293 or CHO cells was investigated using Fura-2-based calcium measurements and whole-cell patch-clamp recordings. Activity of PAP on TRPM8 was further analysed using Fura-2-based calcium imaging on sensory neurons isolated from lumbosacral dorsal root ganglia (DRG) of mice.

KEY RESULTS

PAP rapidly and reversibly inhibits responses of TRPM8 expressed in HEK293 cells to cold and menthol, with IC₅₀ values between 2 and 10 μM. It acts by shifting the voltage dependence of channel activation towards positive potentials, opposite to the effect of menthol. PAP also inhibits TRPM8-mediated, menthol-evoked calcium responses in lumbosacral DRG neurons. At a concentration of 10 μM, PAP did not significantly affect TRPA1, TRPV1, or TRPM3.

CONCLUSION AND IMPLICATIONS

PAP inhibits TRPM8 in a concentration range consistent with PAP levels in the urine of treated patients. Since TRPM8 is expressed in bladder afferent neurons and upregulated in patients with painful bladder disorders, TRPM8 inhibition may underlie the analgesic activity of PAP.

Nitroaromatic Antibiotics as Nitrogen Oxide Sources

Nitroaromatic antibiotics show activity against anaerobic bacteria and parasites, finding use in the treatment of Heliobacter pylori infections, tuberculosis, trichomoniasis, human African trypanosomiasis, Chagas disease and leishmaniasis. Despite this activity and a clear need for the development of new treatments for these conditions, the associated toxicity and lack of clear mechanisms of action have limited their therapeutic development. Nitroaromatic antibiotics require reductive bioactivation for activity and this reductive metabolism can convert the nitro group to nitric oxide (NO) or a related reactive nitrogen species (RNS). As nitric oxide plays important roles in the defensive immune response to bacterial infection through both signaling and redox-mediated pathways, defining controlled NO generation pathways from these antibiotics would allow the design of new therapeutics. This review focuses on the release of nitrogen oxide species from various nitroaromatic antibiotics to portend the increased ability for these compounds to positively impact infectious disease treatment.

OmpW is positively regulated by iron via Fur, and negatively regulated by SoxS contribution to oxidative stress resistance in Escherichia coli

Iron plays a central role at the interface of pathogen and host. The ability to sequester iron from a host not only reduces host immune defenses but also promotes pathogen virulence, leading to the occurrence of infectious disease. Recently, outer membrane protein OmpW was shown to protect bacteria against harsh environmental conditions and to play a role in infectious disease. The expression of this versatile protein is controlled by iron, but the underlying mechanism of iron regulation has not been elucidated. In this study, the relation between OmpW expression and iron was investigated. Our results demonstrated that expression of OmpW is responsive to iron. Iron uptake analysis showed that an ompW mutant strain has a strong requirement for iron as compared to wild type and the ompW complemented strain. Moreover, ferric uptake regulation protein Fur, an iron binding transcriptional factor, was downregulated under iron limitation conditions and had a similar expression profile to OmpW in the presence or absence of iron. Based on these results, we suggest that iron regulates OmpW by binding to Fur. Furthermore, SoxS, a transcriptional factor involved in oxidative stress, was found to negatively regulate OmpW. We found that downregulating or knocking out OmpW results in bacterial resistance to oxidative stress. These findings provide new insight into the regulation of OmpW expression by iron, and may represent a new mechanism contributing to iron-mediated infectious disease.

Evaluating the level of nitroreductase activity in clinical Klebsiella pneumoniae isolates to support strategies for nitro drug and prodrug development

To understand the potential utility of novel nitroreductase (NR)-activated prodrugs, NR enzyme activity was assessed in clinical Klebsiella pneumoniae isolates using a NR-activated fluorescent probe. NR activity was constant throughout the bacterial growth cycle, but individual K. pneumoniae isolates exhibited a wide range of NR activity levels. The genes of major NR enzymes (nfsA and nfnB) showed a number of sequence variants. Aside from a C-terminal extension of NfnB, which may be responsible for lower NR activity in specific isolates, the genetic differences did not explain the variation in activity. Analysis of important clinical strains (ST11, ST258, ST14 and ST101) showed significant variation in NR activity between isolates within the same sequence type despite conservation of nfsA/nfnB sequences. Addition of methyl viologen (MV), a known activator of soxRS, caused a significant increase in NR activity for all strains, with proportionally larger increases in activity seen for strains with low uninduced NR levels. Real-time PCR on selected strains following exposure to MV showed upregulation of soxS (15-32-fold) and nfsA (5-22-fold) in all strains tested. Expression of nfnB was upregulated 2-5-fold in 4/6 strains tested. High levels of NR activity in the absence of MV activation correlated with nitrofurantoin susceptibility. These data provide evidence that NR gene mutations and regulatory pathways influence NR activity in K. pneumoniae isolates and this is likely to impact treatment efficacy with novel nitro-containing drugs or prodrugs.