Molecular events in the activation of B cells and macrophages by a non-microbial TLR4 agonist, G1-4A from Tinospora cordifolia.
G1-4A, a polysaccharide from an Indian medicinal plant Tinospora cordifolia, was recently shown to protect mice against septic shock by modulating the proinflammatory cytokines. G1-4A also activated B cells polyclonally. The present report describes in detail the molecular events associated with G1-4A-induced immunomodulation in vitro and in vivo. G1-4A treatment led to an increase in the CD69 expression in lymphocytes. G1-4A-induced proliferation of B cells was completely inhibited by PI3K inhibitor Ly294002, mTOR inhibitor rapamycin and NF-kappaB inhibitor plumbagin. Akt, ERK and JNK were activated by G1-4A which finally resulted in the activation of IKK, degradation of IkappaB-alpha and translocation of NF-kappaB to the nucleus. Administration of G1-4A to mice led to splenomegaly and an increase in the numbers of T cells, B cells and macrophages. This increase in spleen cellularity was due to in vivo proliferation of lymphocytes and upregulation of anti-apoptotic genes. Anti-TLR4-MD2 complex antibody inhibited G1-4A-induced B cell proliferation and degradation of IkappaB-alpha suggesting that TLR-4 was a receptor for G1-4A on B cells. Activation of RAW 264.7 macrophages by G1-4A was found to be dependent on ERK and NF-kappaB-mediated signals. The phagocytosis index in peritoneal exudate cells (PEC) isolated from G1-4A treated mice was significantly higher as compared to that in PEC from control mice. G1-4A administration also increased the number of CD11b(+) cells in the PEC without an increase in the total number of PEC. Thus the present understanding of the molecular mechanism of action of G1-4A, a novel non-microbial TLR4 agonist, will pave the way for its application as an immunomodulator and adjuvant.
Radiation Biology & Health Sciences Division, Bio-Medical Group, Bhabha Atomic Research Centre, Modular Laboratories, Trombay, Mumbai 400085, India.
Rashmi
R
Raghu
Deepak
D
Sharma
Rupal
R
Ramakrishnan
Shazia
S
Khanam
Gajanan J
GJ
Chintalwar
Krishna Balaji
KB
Sainis
D000276:Adjuvants, Immunologic / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D015703:Antigens, CD / Q000276:immunology / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology / Q000378:metabolism; D001402:B-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D037181:Lectins, C-Type; D008213:Lymphocyte Activation; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D009285:Naphthoquinones / Q000494:pharmacology; D010587:Phagocytosis / Q000187:drug effects / Q000276:immunology; D019869:Phosphatidylinositol 3-Kinases / Q000276:immunology / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry / Q000494:pharmacology*; D011494:Protein Kinases / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000819:agonists / Q000276:immunology / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D013163:Splenomegaly / Q000276:immunology / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases; D031610:Tinospora / Q000737:chemistry; D051197:Toll-Like Receptor 4 / Q000819:agonists* / Q000276:immunology; D000099192:CD69 Antigens
D000276:Adjuvants, Immunologic; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D002352:Carrier Proteins; D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D037181:Lectins, C-Type; D020930:MAP Kinase Kinase Kinases; D009025:Morpholines; D016328:NF-kappa B; D009285:Naphthoquinones; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017853:Phosphotransferases (Alcohol Group Acceptor); D011134:Polysaccharides; D011494:Protein Kinases; D019253:Proto-Oncogene Proteins c-bcl-2; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; D051197:Toll-Like Receptor 4; D000099192:CD69 Antigens; C542611:G1-4A polysaccharide; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C546843:mTOR protein, mouse; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; C014758:plumbagin