Mycobacterium tuberculosis secretory proteins CFP-10, ESAT-6 and the CFP10:ESAT6 complex inhibit lipopolysaccharide-induced NF-kappaB transactivation by downregulation of reactive oxidative species (ROS) production

• Published in: Immunology and cell biology Vol. 86; no. 1; pp. 98 - 106
• Main Authors: Ganguly, Niladri, Giang, Pham H, Gupta, Chitra, Basu, Sandip K, Siddiqui, Imran, Salunke, Dinakar M, Sharma, Pawan
• Format: Journal Article
• Language: English
• Published: United States 01.01.2008
• Subjects: Animals; Antigens, Bacterial - genetics; Antigens, Bacterial - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Cell Line; DNA-Binding Proteins - genetics; Electrophoretic Mobility Shift Assay; Genes, Reporter; Lipopolysaccharides - pharmacology; Macrophages, Peritoneal - immunology; Macrophages, Peritoneal - metabolism; Macrophages, Peritoneal - microbiology; Mice; Mycobacterium tuberculosis - genetics; Mycobacterium tuberculosis - metabolism; NF-kappa B - antagonists & inhibitors; NF-kappa B - genetics; NF-kappa B - metabolism; Reactive Oxygen Species - antagonists & inhibitors; Reactive Oxygen Species - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Signal Transduction - genetics; Transcriptional Activation - drug effects; Tuberculosis - immunology; Tuberculosis - metabolism; Tuberculosis - pathology
• ISSN: 0818-9641; 1440-1711

Mycobacterium tuberculosis (Mtb) causes death of 2-3 million people annually and is considered one of the most successful intracellular pathogens to persist inside the host macrophage. Recent studies have implicated the role of RD-1 region of Mtb genome in the mycobacterial pathogenesis. The role of RD-1-encoded secretory proteins of Mtb in modulation of macrophage function has not been investigated in detail. Here we show that RD-1 encoded two major secretory proteins, namely, culture filtrate protein-10 kDa (CFP-10) and early secreted antigenic target-6 kDa (ESAT-6), and their 1:1 CFP-10:ESAT6 complex inhibit production of reactive oxidative species (ROS) in RAW264.7 cells. These proteins also downregulated the bacterial lipopolysaccharide (LPS)-induced ROS production, which, in turn, downregulated LPS-induced nuclear factor-kappaB (NF-kappaB) p65 DNA-binding activity, as well as inhibited the NF-kappaB-dependent reporter gene (chloramphenicol acetyl transferase) expression in the treated macrophages. Moreover, addition of N-acetyl cysteine, which is a scavenger of ROS, also inhibited LPS-induced reporter gene expression by scavenging the ROS, thereby preventing NF-kappaB transactivation. These studies indicate that the secretory proteins CFP-10, ESAT-6 and the CFP10:ESAT6 complex of Mtb can inhibit LPS-induced NF-kappaB-dependent gene expression via downregulation of ROS production.