title: Neuroprotective mechanisms of minocycline against sphingomyelinase/ceramide toxicity: Roles of Bcl-2 and thioredoxin.
abstract: In this study, we determined whether minocycline may protect rat cortical cultures against neurotoxicity induced by sphingomyelinase/ceramide and explored the underlying mechanisms. We found that minocycline exerted strong neuroprotective effects against toxicity induced by bacterial sphingomyelinase and synthetic C2 ceramide. Minocycline enhanced the production of nitric oxide (NO) with resultant increases in cellular cGMP content. Consistently, minocycline-dependent neuroprotection was abolished by the nitric oxide synthase inhibitor L-N(G)-nitroarginine methyl ester (L-NAME) and the soluble guanylate cyclase (sGC) inhibitor 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ). Western blotting revealed that minocycline restored the expression levels of cGMP-dependent protein kinase (PKG)-1, antioxidative thioredoxin-1, and antiapoptotic Bcl-2 that were down-regulated by bacterial sphingomyelinase. Accordingly, the PKG inhibitor KT5823, the thioredoxin reductase inhibitor 1-chloro-2,4-dinitrobenzene (DNCB), and a Bcl-2 inhibitor significantly abolished the minocycline neuroprotection. The minocycline-dependent restoration of Bcl-2 was abolished by L-NAME, ODQ, and KT5823, but not by DNCB, suggesting the involvement of NO/sGC/PKG but not thioredoxin. Furthermore, minocycline-dependent recovery of thioredoxin-1 was PKG-independent. Taken together, our results indicate that minocycline protects rat cortical neurons against bacterial sphingomyelinase/ceramide toxicity via an NO/cGMP/PKG pathway with induction of Bcl-2 and PKG-independent stimulation of thioredoxin-1.
authors.affiliation: Institute of Brain Science and Brain Research Center, National Yang-Ming University, Taipei City 11221, Taiwan, Republic of China.
authors.forename: Ching-Min
authors.initials: CM
authors.lastname: Tang
authors.forename: Chi-Shin
authors.initials: CS
authors.lastname: Hwang
authors.forename: Shang-Der
authors.initials: SD
authors.lastname: Chen
authors.forename: Ding-I
authors.initials: DI
authors.lastname: Yang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D004137:Dinitrochlorobenzene / Q000378:metabolism / Q000494:pharmacology; D019254:Genes, bcl-2; D008911:Minocycline / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester / Q000378:metabolism / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D010069:Oxadiazoles / Q000378:metabolism / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011810:Quinoxalines / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism*; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D002227:Carbazoles; D002518:Ceramides; D004137:Dinitrochlorobenzene; D018696:Neuroprotective Agents; D010069:Oxadiazoles; D019253:Proto-Oncogene Proteins c-bcl-2; D011810:Quinoxalines; C073601:KT 5823; D009569:Nitric Oxide; D013879:Thioredoxins; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; D013108:Sphingomyelin Phosphodiesterase; D008911:Minocycline; D006152:Cyclic GMP; D019331:NG-Nitroarginine Methyl Ester