Acid sphingomyelinase inhibition suppresses lipopolysaccharide‐mediated release of inflammatory cytokines from macrophages and protects against disease pathology in dextran sulphate sodium‐induced colitis in mice

Abstract

SummaryLipopolysaccharide (LPS) and inflammatory cytokines cause activation of sphingomyelinases (SMases) and subsequent hydrolysis of sphingomyelin (SM) to produce a lipid messenger ceramide. The design of SMase inhibitors may offer new therapies for the treatment of LPS-and cytokine-related inflammatory bowel disease. We synthesized a series of difluoromethylene analogues of SM (SMAs). We report here the effects of the most potent SMase inhibitor, SMA-7, on the LPS-mediated release of tumour necrosis factor-a, interleukin-1b and interleukin-6 from THP-1 macrophages and the pathology of dextran sulphate sodium (DSS)-induced colitis in mice. SMA-7 suppressed the LPS-induced cytokine release and nuclear factorjB activation. LPS stimulation caused a four-fold increase in acid SMase activation, but little increase in neutral SMase activity. The presence of 10 lM SMA-7 caused acid SMase to remain at the control levels and reduced the formation of ceramide. HT-29 cells had significantly decreased cell viability when incubated with media from LPS-stimulated THP-1 macrophages. However, incubating the colon cells in media from both SMA-7 and LPStreated macrophages caused little decrease in viability, suggesting that ceramide has a role in the LPS-stimulated signalling that releases cytotoxic factors against colon cells. Oral administration of SMA-7 to mice with 2% DSS in the drinking water, for 10 or 21 consecutive days, reduced significantly the cytokine levels in the colon and the severity of colonic injury. These findings suggest a central role for acid SMase/ceramide signalling in the pathology of DSS-induced colitis in mice, indicating a possible preventive or therapeutic role for SMase inhibitor in inflammatory bowel disease.

Mechanism of Glycosaminoglycan-Mediated Bone and Joint Disease

“…In addition, MPS synovial cells have elevated levels of the prosurvival lipid, S1P, contributing to the enhanced proliferation rate. Changes in the production of the signaling lipids, ceramide and S1P, are known consequences of LPS signaling, 26,27,37 supporting our central hypothesis. Osteopenia, in addition to other bone lesions, has been observed in some of the MPS disorders, including MPS VI.…”

Defining a Role for Acid Sphingomyelinase in the p38/Interleukin-6 Pathway

“…Previous studies have used ASM Ϫ/Ϫ peritoneal macrophages, showing no requirement of ASM for the production of various inflammatory mediators, including nitric oxide, TNF␣, and IL-1␤ (13,32). Conversely, a transcriptional inhibitor of ASM, SMA-7, was shown to reduce cytokine production, although the specificity of this inhibitor has not been well established (14). Additionally, while this work was in progress, Kumagai et al (15) showed involvement of ASM in the synergistic production of IL-6 in response to carcinogenic electrophiles with TNF␣ but not TNF␣ alone in bladder cancer cells, where these electrophiles resulted in ASM up-regulation.…”

“…Conversely, previous work from our laboratory has demonstrated that IL-6 production and p38 activation are negatively regulated by GBA1-derived ceramide in MCF-7 cells (12). Literature related to ASM has shown that ASM is not required for p38 signaling in ASM Ϫ/Ϫ murine macrophages (13), whereas other work has indicated a role for ASM in cytokine production, including IL-6, with the use of an SM-based ASM inhibitor (14). While this work was in progress, Kumagai et al (15) showed that ASM is involved in IL-6 production in bladder cancer cells; however, a signaling pathway leading to IL-6 was not identified, underscoring the need to identify signaling pathways that ASM regulates to affect IL-6 secretion.…”

Ceramide and Ceramide 1-Phosphate Are Negative Regulators of TNF-α Production Induced by Lipopolysaccharide

“…A few reports have indicated a positive role of the ASMase-released ceramide in the macrophage responses to LPS. Direct and indirect (by targeting an upstream phospholipase C) inhibition of ASMase suppressed the LPS-induced ceramide production, recruitment of TLR4 to lipid rafts, activation of NF-kB (a transcription factor playing an essential role in the induction of inflammatory mediators), and cytokine release from THP-1 cells (23,24). Quite to the contrary, C8-ceramide reduced TNF-a and IL-6 but not IL-10 production in LPS-stimulated macrophages exhibiting simultaneously an opposite effect in mast cells (25), whereas C6-ceramide inhibited LPS-stimulated IL-8 production in human aortic endothelial cells (26).…”