Search

Sphingolipids (SLs) are amphiphilic molecules mainly associated with the external leaflet of eukaryotic plasma membrane, and are structural membrane components with key signaling properties. Since the beginning of the last century, a large number of papers described the involvement of these molecules in several aspects of cell physiology and pathology. Several lines of evidence support the critical role of SLs in inflammatory diseases, by acting as anti‐ or pro‐inflammatory mediators. They are involved in control of leukocyte activation and migration, and are recognized as essential players in host response to pathogenic infection. We propose here a critical overview of current knowledge on involvement of different classes of SLs in inflammation, focusing on the role of simple and complex SLs in pathogen‐mediated inflammatory response.

Gene therapy vectors derived from subgroup C adenoviruses of the serotype 5 (Ad5) and 2 (Ad2) resulted in inefficient infection of well differentiated respiratory cells, both in vitroand in vivo. The level of expression and localization of the primary receptor for Ad5 and Ad2, termed CAR, do not completely explain why the infection efficiency varies greatly in different experimental conditions. The possibility that additional receptors like proteoglycans are involved in the infection of Ad5 and Ad2 was investigated, because several pathogenic microorganisms use heparan sulfate–glycosaminoglycans (HS-GAGs) as coreceptors for multistep attachment to target cells. The HS-GAG analog heparin decreased Ad5- and Ad2-mediated infection and binding starting from the concentration of 0.1 μg/ml, up to a maximum of 50%. A similar reduction in Ad5 binding and infection was obtained by treatment of cells with heparin lyases I, II, and III but not with chondroitin ABC lyase. The effect of heparin on Ad5 binding has not been observed in surface GAG-defective Raji cells and after treating A549 cells with heparin lyases I, II ,and III. The binding of Ad5 was completely abolished when both CAR was blocked with RmcB antibody and HS-GAGs were competitively inhibited by heparin. Parallel experiments demonstrate that HS-GAGs are irrelevant to binding and infection of the subgroup B adenovirus type 3. Collectively, these results demonstrate for the first time that HS-GAGs expressed on the cell surface are involved in the binding of Ad5 and Ad2 to host cells.

The regulation of chloride conductance was investigated in the T84 human colon carcinoma cell line by the quenching of the fluorescent probe 6‐methoxy‐N‐(3‐sulfopropyl)quinolinium. The permeable cAMP analog 8‐Br‐cAMP (100 μ) and the calcium ionophore ionomycin (1 μM) activate a chloride conductance. A prolonged (4 h) preincubation of cells with phorbol 12‐myristate 13‐acetate (100 nM) or with the diacylglycerol analog 1‐oleoyl‐2‐acetyl‐glycerol (100 μM): (1) down‐modulates to almost zero the protein kinase C activity in the membranes; (ii) inhibits the activation of the chloride conductance mediated by 8‐Br‐cAMP but not by calcium; (iii) reduces the mRNA without changing the expression of the protein product of the cystic fibrosis gene. The data suggest that PKC is essential for the activation of the cAMP‐dependt chloride conductance in T84 cells.

Following cystic fibrosis (CF) neonatal screening implementation, a high frequency of heterozygotes has been reported among neonates with elevated immunoreactive trypsinogen (IRT) and normal sweat chloride levels. We studied the relationship between normal IRT values and CF heterozygosity: 10,000 neonates were screened for CF by IRT measurement and tested for 40 CF mutations; the 294 carriers detected were coupled with newborns negative to the same genetic testing, and the two groups' IRT levels compared. Heterozygotes had higher IRT levels than their controls (mean 35.32 vs. 27.58 μg/L, P < 0.001). Even within normal trypsinogen range, the probability of being a CF carrier increases with neonatal IRT concentration. © 2005 Wiley‐Liss, Inc.