Incorporation of sodium channel blocking and free radical scavenging activities into a single drug, AM-36, results in profound inhibition of neuronalapoptosis
Jk. Callaway et al., Incorporation of sodium channel blocking and free radical scavenging activities into a single drug, AM-36, results in profound inhibition of neuronalapoptosis, BR J PHARM, 132(8), 2001, pp. 1691-1698
1 AM-36 is a novel neuroprotective agent incorporating both antioxidant and
Na+ channel blocking actions. In cerebral ischaemia, loss of cellular ion
homeostasis due to Na+ channel activation, together with increased reactive
oxygen species (ROS) production, are thought to contribute to neuronal dea
th. Since neuronal death in the penumbra of the ischaemic lesion is suggest
ed to occur by apoptosis, we investigated the ability of AM-36, antioxidant
s and Na+ channel antagonists to inhibit toxicity induced by the neurotoxin
, veratridine in cultured cerebellar granule cells (CGC's).
2 Veratridine (10-300 muM) concentration-dependently reduced cell viability
of cultured CGC's. Under the experimental conditions employed, cell death
induced by veratridine (100 muM) possessed the characteristics of apoptosis
as assessed by morphology, TUNEL staining and DNA laddering on agarose gel
s.
3 Neurotoxicity and apoptosis induced by veratridine (100 muM) were inhibit
ed to a maximum of 50% by the antioxidants, U74500A (0.1 - 10 muM) and U838
36E (0.03 - 10 muM), and to a maximum of 30% by the Na+ channel blocker, di
bucaine (0.1-100 muM). In contrast, AM-36 (0.01-10 muM) completely inhibite
d veratridine-induced toxicity (IC50 1.7 (1.5-1.9) muM, 95% confidence inte
rvals (CI) in parentheses) and concentration-dependently inhibited apoptosi
s.
4 These findings suggest veratridine-induced toxicity and apoptosis are par
tially mediated by generation of ROS. AM-36, which combines both Na+ channe
l blocking and antioxidant activity, provided superior neuroprotection comp
ared with agents possessing only one of these actions. This bifunctional pr
ofile of activity may underlie the potent neuroprotective effects of AM-36
recently found in a stroke model in conscious rats.