NAD(P)H autofluorescence induction by Compound C in rat carotid chemoreceptor cells

Abstract

Compound C (CC) has been known as an inhibitor of AMP‐activated kinase (AMPK). Recently other roles of CC have been reported. CC inhibits hypoxia dependent HIF‐1α activation independent of AMPK but dependent on mitochondrial electron transport chain (ETC) (Emerling 07) and CC functions as an inhibitor of complex I of ETC (Chua 11). In addition, we have found that CC (4μM) produces ~10 fold increase in NAD(P)H autofluorescence (AutoFlu) as compared to hypoxia or cyanide in rat carotid body (CB) glomus cells. Autoflu was detected with 360/50 excitation(x) and 460/50 emission(m) filters. The effect of CC on the hypoxic [Ca2+]i response was observed by using 340&380x with 540/50m filter for fura‐2. Rat CB glomus cells were identified with rhodamine‐tagged peanut agglutinin.Results1) AutoFlu produced by CC is dose dependent, reaching a plateau at 0.04μM in both CB type cells. 2) The magnitude of AutoFlu induced by CC was greater in glomus cells compared to non‐glomus cells. 3) AutoFlu induced by 0.4μM CC was reduced ~50% by hypoxia but only < 10% by 20mM KCl. 4) CC did not increase calcium despite the increase in AutoFlu. 5) 0.4μM CC reduced the hypoxia‐induced [Ca2+]i increase by ~50%, but did not block 20mM KCl‐induced [Ca2+]i increase. These preliminary results suggest that CC induced significant NAD(P)H AutoFlu, which may significantly affect the measured [Ca2+]i response to hypoxia in glomus cells. (Funded by NIH HL54621)