Retinal ganglion cell survival is enhanced by gabapentin-lactam in vitro: evidence for involvement of mitochondrial KATP channels.
BACKGROUND
Recently, gabapentin-lactam (GBP-L) was shown to be neuroprotective in vivo. It has been suggested that GBP-L may act by opening mitochondrial ATP-sensitive potassium (K(ATP)) channels. We tested this hypothesis by quantifying the effect of GBP-L on the survival of purified retinal ganglion cells (RGCs).


METHODS
RGCs were purified from early postnatal rat retinae by immunopanning with antibodies against Thy1.1 and cultured in serum-free medium for 2 days. Cell survival was quantified by counting vital cells under phase-contrast optics. Results were normalized to controls. RGCs were treated with various concentrations (3.2-320 microM) of GBP-L with and without 1 microM glibenclamide, blocking both plasmalemmal and mitochondrial K(ATP) channels, or 100 microM 5-hydroxydecanoate (5-HD), antagonizing selectively mitochondrial K(ATP) channels. For comparison, additional cultures were treated with 32 microM gabapentin, the parent drug of GBP-L. A combination of the neurotrophic factors BDNF and CNTF (50 ng/ml each) served as a positive control. RESULTS. GBP-L increased RGC survival to a maximum of 145+/-5% (mean +/- SEM) in a concentration-dependent manner. The pEC(50) was 5.0, CI95 [4.7, 5.3]. Preincubation with glibenclamide changed the dose-response of GBP-L, indicating that it acted as a competitive antagonist with a pA2 value of 6.8, CI95 [5.9, 7.5]. 5-HD completely blocked the survival-promoting effect of GBP-L. Gabapentin had no effect, whereas the combination of CNTF and BDNF enhanced survival to 177+/-9%.


CONCLUSIONS
GBP-L, but not gabapentin, can promote the survival of cultured central nervous system neurons, possibly by opening mitochondrial K(ATP) channels. These results suggest further testing of GBP-L as a potentially neuroprotective drug.
Pielen
Amelie
A
Department of Neuroophthalmology, Albert-Ludwig University of Freiburg, Killianstrasse 5, 79106 Freiburg, Germany.
Kirsch
Matthias
M
Hofmann
Hans-Dieter
HD
Feuerstein
Thomas J
TJ
Lagrèze
Wolf A
WA
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001372:Aza Compounds / Q000494:pharmacology*; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D002469:Cell Separation; D002470:Cell Survival / Q000187:drug effects; D020934:Ciliary Neurotrophic Factor / Q000494:pharmacology; D003652:Decanoic Acids / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D006880:Hydroxy Acids / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000378:metabolism; D013141:Spiro Compounds / Q000494:pharmacology*
D001372:Aza Compounds; D019208:Brain-Derived Neurotrophic Factor; D020934:Ciliary Neurotrophic Factor; D003652:Decanoic Acids; D006880:Hydroxy Acids; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013141:Spiro Compounds; C404763:gabapentin-lactam; C052853:5-hydroxydecanoic acid; D000255:Adenosine Triphosphate; D005905:Glyburide