isoglobotrihexosylceramide and Inflammation

Gaucher disease (GD) is associated with upregulation of CD1d and MHC-class II expression by monocytes. While the physiological impact of CD1d upregulation remains uncertain, it has been proposed that MHC-class II upregulation is associated with inflammation. Hereby, we show that the decrease in MHC-class II expression seen in GD patients under therapy correlates positively with chitotriosidase activity, a marker of inflamed macrophages. We also show that retinoic acid (RA) and the beta-glucocerebrosidase inhibitor conduritol-B-epoxide (CBE) lead to upregulation of CD1d expression by THP-1 cells, which correlated with an increase in mRNA expression. In vitro co-culture experiments showed that RA treated THP-1 cells were more stimulatory for CD4(+) than for CD8(+) T cells, as determined by CFSE loss, in comparison to untreated THP-1 cells. Interestingly, even though addition of exogenous isoglobotrihexosylceramide (iGb3), a physiological CD1d ligand, augmented the percentage of dividing CD4(+) T cells, we could not detect a significant expansion of CD4(+)Valpha24(+) invariant Natural Killer T (iNKT) cells. In contrast, addition of alpha-galactosylceramide (alpha-GC) induced expansion of Valpha24(+) iNKT cells as determined by using alpha-GC-loaded human CD1d dimers. These results strengthen the existence of a cross-talk between monocyte lipid accumulation, inflammation and changes in cell surface CD1d and MHC-class II in monocytes, which may result in inappropriate recognition events by immune cells and perpetuate chronic inflammation.

Topics: Antigens, CD1d; Antineoplastic Agents; CD4-Positive T-Lymphocytes; CD8-Positive T-Lymphocytes; Cell Division; Cell Line; Chronic Disease; Coculture Techniques; Enzyme Inhibitors; Gaucher Disease; Globosides; Hexosaminidases; Histocompatibility Antigens Class II; Humans; Inflammation; Inositol; Monocytes; Natural Killer T-Cells; Protein Multimerization; RNA, Messenger; Tretinoin; Trihexosylceramides; Up-Regulation

Apolipoprotein E (apoE), a component of plasma lipoproteins, plays an important, but poorly defined role in sepsis. We have shown that injecting apoE increases septic mortality in a rat model of gram-negative bacterial sepsis, with concomitant hepatic natural killer T (NKT) cell proliferation and activation. The presumed mechanism for this apoE-mediated mortality is that apoE can bind and traffic antigens, presumed to include lipopolysaccharide (LPS), and promote activation of dendritic cells (DC) with subsequent NKT activation and cytokine release. Thus, we sought to prove that LPS was the antigen responsible for the increased NKT activation enhanced by the presence of apoE.. We isolated murine marrow-derived DCs, pulsed them with lipid antigen (LPS, and positive controls alpha-galactosylceramide [alpha-GalCer] and isoglobotrihexosylceramide 3 [iGb3]) with or without apoE, and then cocultured the DCs with hybridoma NKTs. NKT activation was measured by interleukin-2 (IL-2) supernatant levels using enzyme-linked immunosorbent assay (ELISA).. LPS at different concentrations was a weak stimulus for NKT activation regardless of apoE presence. When apoE was present, iGb3, an endogenous ligand analog, elicited more than a 2-fold increase in IL-2 response when compared with iGb3 alone (P < .05).. These results indicate an endogenous ligand, not LPS, may be responsible for NKT activation. A molecular remnant similar to iGb3 could act as a damage-associated molecular pattern and play a prominent role in animal models of sepsis.

Topics: Animals; Apolipoproteins E; Enzyme-Linked Immunosorbent Assay; Globosides; Gram-Negative Bacterial Infections; Hepatocytes; Inflammation; Interleukin-2; Killer Cells, Natural; Rats; Sepsis; Trihexosylceramides