Impediment to calcium influx and reactive oxygen production accounts for the inhibition of neutrophil Mac-1 Up-regulation and adhesion by tetrandrine.
We studied the mechanisms by which the plant alkaloid tetrandrine (TTD) inhibits Mac-1-dependent neutrophil adhesion to fibrinogen. TTD (0.1-10 microM) significantly inhibited Mac-1 up-regulation and neutrophil adhesion, as induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol-myristate-acetate (PMA). Treatment of neutrophils with fMLP or PMA caused a rapid influx of Ca++ and accumulation of reactive oxygen species (ROS), both of which have been shown to enhance neutrophil adhesion via Mac-1 up-regulation. Because TTD antagonizes Ca++ influx and abrogates ROS, we examined the relationship between Ca++ influx, ROS formation, and Mac-1 expression in TTD-inhibited neutrophil adhesion. TTD alone caused a slight but statistically significant increase in [Ca++]i with no effect on adhesion. In contrast, TTD as well as two Ca++ channel antagonists, verapamil and nifedipine, markedly diminished fMLP- and PMA-induced Ca++ influx, Mac-1 up-regulation, and adhesion. TTD also inhibited increases in [Ca++]i and adhesion induced by the ionophore A23187 but failed to inhibit those induced by thapsigargin, an agent mobilizing Ca++ from intracellular stores. Thus, TTD impeded Ca++ influx from outward to avert neutrophil adhesion. Similarly, TTD and two ROS scavengers, superoxide dismutase and catalase, abolished ROS production, Mac-1 up-regulation, and neutrophil adhesion. Ca++ and ROS, therefore, represent two essential signals for Mac-1 up-regulation upon fMLP or PMA stimulation. Our data suggest that the antiadherent effect of TTD is mediated, in part, by the inhibition of Ca++ influx and ROS formation, resulting in suppressed up-regulation of Mac-1 and, in turn, neutrophil adhesion to fibrinogen.
Shen
Y C
YC
Institute of Pharmacology, School of Life Science, National Yang-Ming University, Taipei, Taiwan, Republic of China.
Chen
C F
CF
Wang
S Y
SY
Sung
Y J
YJ
D000328:Adult; D000470:Alkaloids / Q000494:pharmacology*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D044182:Benzylisoquinolines; D002118:Calcium / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D005260:Female; D006801:Humans; D016177:Macrophage-1 Antigen / Q000502:physiology*; D008297:Male; D009504:Neutrophils / Q000187:drug effects* / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015854:Up-Regulation
D000470:Alkaloids; D000894:Anti-Inflammatory Agents, Non-Steroidal; D044182:Benzylisoquinolines; D016177:Macrophage-1 Antigen; D017382:Reactive Oxygen Species; C009438:tetrandrine; D002118:Calcium