Bladder urothelial BK channel activity is a critical mediator for innate immune response in urinary tract infection pathogenesis

Abstract

The open probability of calcium-activated voltage-gated potassium channel (BK channel) on bladder umbrella urothelial cells is increased by lipopolysaccharide (LPS). It is hypothesized that this channel’s activity is important in the urothelial innate immune response during urinary tract infection (UTI). We performed in vivo studies using female C57BL/6 mice whose bladders were inoculated with LPS (150 μl of 1 mg/ml) or uropathogenic Escherichia coli (UPEC, UTI89), without and with intravesical BK inhibitor iberiotoxin (IBTX, 1 μM). Inflammatory biomarkers (chemokines and cytokines) were measured in urine specimens collected 2 h after inoculation using a 32-multiplex ELISA. Of these 32 biomarkers, 19 and 15 were significantly elevated 2 h after LPS and UPEC exposure, respectively. IBTX significantly abrogated the elevations of 15 out of 19 biomarkers after LPS inoculation and 12 out of 15 biomarkers after UPEC inoculation. In a separate experiment, qPCR for IL-6, interferon-γ-induced protein 10 (CXCL10), and macrophage inflammatory protein 2 (CXCL2) in urothelium paralleled the changes measured in urine of these same biomarkers, supporting that urinary changes in biomarker levels reflected urothelial expression changes. These in vivo data demonstrated that BK channel activity is crucial in the urothelial host innate immune response, as measured by changes in urinary biomarkers, in UTI pathogenesis.

The nitric oxide‐cyclic guanosine monophosphate pathway inhibits the bladder ATP release in response to a physiological or pathological stimulus

“…The reason why the effect of sildenafil on lysosomal exocytosis of ATP induced by LPS was partial might be that the production of 8‐nitro‐cGMP is primarily dependent on the nitration reaction rather than the amount of cGMP. Another possible reason is that LPS activates a diversity of signaling pathways; LPS induces the release of multiple cytokines (Yeh et al, 2019), some of which may evoke NO insensitive ATP release. In any case, activation of the NO‐cGMP pathway could partially, but significantly attenuate bladder hyperactivity in cystitis.…”

Transcriptomic analyses and experimental verification reveal potential biomarkers and biological pathways of urinary tract infection

“…SAA1 can prevent UPEC’s invasion of urothelial cells and the formation of biofilms [ 25 ]. CXCL1 and CXCL10 are also involved in the immune inflammatory response in UTIs [ 26 , 27 ].…”

Large-conductance calcium-activated potassium channels mediate lipopolysaccharide-induced activation of murine microglia

“…Although little is known about the role of the BK channel in microglia activation, it is well-studied in macrophages. BK channel activation is associated with the proinflammatory effect of macrophages induced by various stimuli, including LPS (17)(18)(19)(20), heparin sulfate (21), and uropathogenic Escherichia coli (20), and it facilitates LPS and interleukin-1␤-induced adhesion of monocytes to endothelial cells (22,23). BK channel inhibition significantly reduced interleukin-1␤ production in LPS-primed mouse Schwann cells and THP-1 macrophage (24, 25), and it might cause impaired inflam-…”

“…masome activation in human and mouse macrophage and dendritic cells (25). BK channel blockers were able to suppress myelin phagocytosis of LPS-activated rat macrophages (26) and abrogate the elevations of some inflammatory biomarkers (chemokines and cytokines) in urine specimens of mice whose bladders were inoculated with LPS or uropathogenic E. coli (20). During an early step in macrophage activation, the PM BK channel is activated by LPS (17,27), which is essential for LPSinduced NF-B activation and cytokine production (18).…”