Normalization of the levels of inflammatory molecules in Mycobacterium smegmatis-infected U937 cells by fibrate pretreatment

BACKGROUND: Tuberculosis (TB) is a respiratory tract disease caused by Mycobacterium tuberculosis infection. M. tuberculosis exploits immune privilege to grow and divide in pleural macrophages. Fibrates are associated with the immune response and control lipid metabolism through glycolysis with ß-oxidation of fatty acids. RESULTS: In this study, we investigated the effect of fibrate pretreatment on the immune response during M. smegmatis infection in U937 cells, a human leukemic monocyte lymphoma cell line. The protein expression of tumor necrosis factor α (TNF-α), an inflammatory marker, and myeloid differentiation primary response gene 88 (MyD88), a toll like receptor adaptor molecule, in the infected group increased at 1 and 6 h after M. smegmatis infection of U937 cells. Acetyl coenzyme A acetyl transferase-1 (ACAT-1), peroxisome proliferator-activated receptor-α (PPAR-α), TNF-α, and MyD88 decreased in U937 cells treated with fibrates at 12 and 24 h after treatment. More than a 24 h pretreatment with fibrate resulted in similar expression levels of ACAT-1 and PPAR-α between infected vehicle control and infected groups which were pretreated with fibrate for 24 h. However, upon exposure to M. smegmatis, the cellular expression of the TNF-α and MyD88 in the infected groups pretreated with fibrate for 24 h decreased significantly compared to that in the infected vehicle group. CONCLUSION: These results suggest that fibrate pretreatment normalized the levels of inflammatory molecules in Mycobacterium smegmatis-infected U937 cells. Further studies are needed to confirm the findings on pathophysiology and immune defense mechanism of U937 by fibrates during M. tuberculosis infection.

Functional and biosynthetic aspects of sialic acid diversity.

Sialic acids comprise a large family of N- and O-substituted neuraminic acid derivatives as components of glycoconjugates. N-Glycolylneuraminic acid is formed from N-acetylneuraminic acid by the action of the CMP-N-acetylneuraminic acid hydroxylase studied in various animals. O-Methylated sialic acids originate from the action of S-adenosylmethionine-8-O-methyltransferase studied in starfish. Sialic acids are O-acetylated at diverse positions by the action of acetyl-CoA-4-O- and -7-O-acetyltransferases found in various animals and, leading to the O-acetylation of sialic acid glycerol side chain, also in man. Some properties of these enzymes are described and biological implications discussed.