III. Nitric oxide mediates the action of lipoteichoic acid on the function of human urothelial cells

Abstract

Gram-positive bacteria are recognized pathogens in urinary tract infections. Lipoteichoic acids, major components of the cell wall of gram-positive bacteria, are important virulence attributes, but their mechanism of action is not well understood. We have postulated that infection-induced altered function of progenitors of urothelial cells (UT) residing in the basal layer is likely to have long-lasting effects on the architecture and function of the urothelium. Our earlier in vitro studies in UT of basal type, grown under growth restricting conditions, have shown that 1) treatment with lipoteichoic acid from Streptococcus faecalis (LT-2) stimulates a subpopulation of progenitors of urothelial cells to proliferate, and 2) resulting large colonies differentiated at an increased rate under conditions simulating those in the basal layer of the urothelium. The hypothesis underlying the present studies was that nitric oxide (NO) mediated LT-2 action on these functions of UT. Immunocytochemical studies using an antibody against inducible nitric oxide synthase (iNOS) confirmed expression of iNOS in LT-2-treated UT. Our hypothesis was tested by treating UT grown under growth restricting conditions (0.005% bovine pituitary extract) with LT-2 (25 micrograms/ml), in the presence or absence of inhibitors of NOS (1 mM NG-nitro-L-arginine methyl ester [L-NAME]; 1 microM dexamethasone [DEXA]) or 25 microM hemoglobin, a potent inactivator of NO. Treatment with LT-2 in the presence of these agents prevented the following effects of LT-2 alone: 1) the stimulatory effect on proliferation of single cells, as well as within the resulting large colonies; 2) the subsequent differentiation of large colonies resulting from this proliferative activity, as indicated by distribution of beta 1 subunit-containing integrins to cell-cell contacts; 3) the inhibitory effect on the subsequent ability of LT-2-treated UT to attach to extracellular matrix proteins. These studies suggest that induction of NOS by LT-2, initially aimed at restricting the replication of infectious agents, may have potential cost of damage to the host bladder by interfering with urothelial differentiation.

Prostasin attenuates inducible nitric oxide synthase expression in lipopolysaccharide-induced urinary bladder inflammation

“…The eNOS-related early-phase NO production is believed to have a beneficial effect, probably in killing bacteria (12). But the late-phase NO production seen in bacterial infection of the bladder, mediated via iNOS after the majority of the invading bacteria is cleared (34), may play different roles such as promoting urothelial cell apoptosis/shedding and interfering with urothelial cell differentiation (14). These roles or events are potentially intensified by a downregulation of in situ urothelial prostasin expression.…”

Morphological and Biochemical Investigation of Nitric Oxide Synthase and Related Enzymes in the Rat and Pig Urothelium

“…In addition, as shown in the present study, urothelial cells may represent an additional source of NO production during bladder infection. Induction of NOS is proposed to have cytotoxic properties against invading pathogens or tumor cells (Nathan and Xie 1994), but it may have a potential cost of damage to the host bladder by interference of NO with urothelial cell differentiation (Elgavish et al 1996; Souza-Fiho et al 1997). Indeed, urothelial cells may be targets for NO, as revealed by their immunoreactivity to cGMP (Smet et al 1996).…”

Inhibition of neuronal M2 muscarinic receptor function in the lungs by extracellular nitric oxide

“…Some tissues were treated with the NOS inhibitor, N G ‐monomethyl‐ L ‐arginine methyl ester ( L ‐NMMA, 10 −5 M ). Other tissues were treated with the NO donor 3‐morpholino‐sydnonimine (SIN‐1; 10 −5 M ), or with haemoglobin (10 −5 M ), a scavenger of extracellular NO ( Elgavish et al ., 1996 ). In some tissues airway epithelium was removed by passing a rolled kimwipe through the tracheal lumen three times prior to segmenting the trachea into rings.…”