Mechanism of macrophage activation by (1,4)-alpha-D-glucan isolated from Tinospora cordifolia.
The signaling mechanism of the novel (1,4)-alpha-D-glucan (RR1) isolated from the medicinal plant Tinospora cordifolia was investigated in macrophages to evaluate its immunostimulating properties. When RAW264.7 macrophages were incubated with RR1 at 4 degrees C, the novel glucan inhibited the phagocytosis of unopsonized zymosan A bioparticles in a dose-dependent manner. RR1 also inhibited the binding and internalization of opsonized zymosan A bioparticles, although at a lower level than laminarin. Incubation of macrophages with anti-CD11b mAb followed by RR1 failed to show any inhibitory effect on RR1-induced TNF-alpha synthesis confirming that complement receptor 3 (CR3) is not involved in the opsonic binding and internalization of RR1 in macrophages unlike zymosan A. The anti-CD11b mAb has significant inhibitory effect on the zymosan A-induced tumor necrosis factor (TNF)-alpha synthesis. RR1 induced TNF-alpha synthesis in macrophages in a dose-dependent manner which can be completely inhibited by the NF-kappaB inhibitor caffeic acid phenethyl ester (CAPE) or curcumin. RR1 activated NF-kappaB in a time- and dose-dependent manner and this modulation of nuclear NF-kappaB activity is associated with the degradation of I-kappaB alpha thus facilitating the translocation of NF-kappaB into the nucleus. RR1-induced NF-kappaB activity peaks at 8 h of RR1 stimulation while I-kappaB alpha degradation occurred within 1 h of stimulation. RR1-induced NF-kappaB activation occurred through TLR6 signaling as evidenced by the synthesis of IL-8 in TLR6-transfected HEK293 cells. These results show that the novel (1,4)-alpha-D-glucan from Tinospora cordifolia activates the immune system through the activation of macrophages that occurs through TLR6 signaling, NF-kappaB translocation and cytokine production.
Nair
P K Raveendran
PK
Research Institute, Miami Children's Hospital, Miami, FL 33155, USA.
Melnick
Steven J
SJ
Ramachandran
Reshma
R
Escalon
Enrique
E
Ramachandran
Cheppail
C
D000818:Animals; D002460:Cell Line; D005936:Glucans / Q000494:pharmacology*; D006801:Humans; D020672:I-kappa B Proteins / Q000276:immunology; D008262:Macrophage Activation / Q000187:drug effects*; D016177:Macrophage-1 Antigen / Q000276:immunology; D051379:Mice; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000276:immunology*; D010587:Phagocytosis / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D031610:Tinospora / Q000737:chemistry; D051216:Toll-Like Receptor 6 / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
D005936:Glucans; D020672:I-kappa B Proteins; D016177:Macrophage-1 Antigen; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; C495368:TLR6 protein, human; D051216:Toll-Like Receptor 6; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; C040088:1,4-glucan