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Ceramides mediate crucial cellular processes including cell death and inflammation and have recently been implicated in inflammatory bowel disease. Ceramides consist of a sphingoid long‐chain base to which fatty acids of various length can be attached. We now investigate the effect of alerting the ceramide acyl chain length on a mouse model of colitis. Ceramide synthase (CerS) 2 null mice, which lack very‐long acyl chain ceramides with concomitant increase of long chain bases and C16‐ceramides, were more susceptible to dextran sodium sulphate‐induced colitis, and their survival rate was markedly decreased compared with that of wild‐type littermates. Using mixed bone‐marrow chimeric mice, we showed that the host environment is primarily responsible for intestinal barrier dysfunction and increased intestinal permeability. In the colon of CerS2 null mice, the expression of junctional adhesion molecule‐A was markedly decreased and the phosphorylation of myosin light chain 2 was increased. In vitro experiments using Caco‐2 cells also confirmed an important role of CerS2 in maintaining epithelial barrier function; CerS2‐knockdown via CRISPR‐Cas9 technology impaired barrier function. In vivo myriocin administration, which normalized long‐chain bases and C16‐ceramides of the colon of CerS2 null mice, increased intestinal permeability as measured by serum FITC‐dextran levels, indicating that altered SLs including deficiency of very‐long‐chain ceramides are critical for epithelial barrier function. In conclusion, deficiency of CerS2 influences intestinal barrier function and the severity of experimental colitis and may represent a potential mechanism for inflammatory bowel disease pathogenesis.

Ceramide synthase 2 (CERS2) is the gene identified from a human liver cDNA library in 2001. Our previous studies have shown higher expression of CERS2 in the breast cancer patients was associated with fewer lymph node metastases. However, the molecular mechanism of CERS2 involved is unknown. Here, we found CERS2 was heterogeneously expressed in various breast cancer cells. The mRNA and protein expression levels of CERS2 in MCF7 cells, which are poorly invasive breast cancer cells, were obviously higher than that in the highly invasive cells MDA-MB-231. Results showed overexpression of CERS2 in MDA-MB-231 cells could significantly inhibit the migration and invasion ability, whereas CERS2 knockdown in MCF7 cells could significantly increase the migration and invasion ability. Overexpression of CERS2 in MDA-MB-231 cells significantly reduced the V-ATPase activity, increased the extracellular pH and decreased the pH-dependent activity of MMP-2 and MMP-9 matrix metalloproteinases (MMPs). CERS2 knockdown in MCF7 cells significantly increased the V-ATPase activity, decreased the extracellular pH and increased the activity of MMP-2 and MMP-9. Taken together, CERS2 can significantly inhibit breast cancer cell invasion and is associated with the decrease of the V-ATPase activity and extracellular hydrogen ion concentration, and in turn the activation of secreted MMP-2/MMP-9 and degradation of extracellular matrix (ECM), which ultimately suppressed tumor's invasion. Thus, CERS2 may represent a novel target for selectively disrupting V-ATPase activity and the invasive potential of cancer cells. J. Cell. Biochem. 116: 502–513, 2015. © 2014 Wiley Periodicals, Inc.