title: Selective regulation of 3 alpha-hydroxysteroid oxido-reductase expression in dorsal root ganglion neurons: a possible mechanism to cope with peripheral nerve injury-induced chronic pain.
abstract: The enzyme 3alpha-hydroxysteroid oxido-reductase (3alpha-HSOR) catalyzes the synthesis and bioavailability of 3alpha,5alpha-neurosteroids as allopregnanolone (3alpha,5alpha-THP) which activates GABA(A) receptors and blocks T-type calcium channels involved in pain mechanisms. Here, we used a multidisciplinary approach to demonstrate that 3alpha-HSOR is a cellular target the modulation of which in dorsal root ganglia (DRG) may contribute to suppress pain resulting from peripheral nerve injury. Immunohistochemistry and confocal microscope analyses showed 3alpha-HSOR-immunostaining in naive rat DRG sensory neurons and glial cells. Pulse-chase, high performance liquid chromatography and Flo/One characterization of neurosteroids demonstrated 3alpha,5alpha-THP production in DRG. Behavioral methods allowed identification of pain symptoms (thermal and mechanical hyperalgesia and/or allodynia) in rats subjected to sciatic nerve chronic constriction injury (CCI). Reverse transcription and real-time polymerase chain reaction revealed that 3alpha-HSOR mRNA concentration in CCI-rat ipsilateral DRG, 5-fold higher than in contralateral DRG, was also 4- to 6-fold elevated than that in sham-operated or naive rat DRG. Consistently, Western blotting confirmed increased 3alpha-HSOR protein levels in CCI-rat ipsilateral DRG and double immunolabeling showed that 3alpha-HSOR overexpression occurred in DRG neurons but not in glia. Functional plasticity of 3alpha-HSOR leading to increased 3alpha,5alpha-THP production was evidenced in CCI-rat DRG. Interestingly, behavioral and molecular time-course investigations revealed that 3alpha-HSOR gene upregulation was correlated to pain symptom development. Most importantly, in vivo knockdown of 3alpha-HSOR expression in healthy rat DRG using 6-carboxyfluorescein-3alpha-HSOR-siRNA exacerbated thermal and mechanical pain perceptions. This paper is the first to show that siRNA-induced knockdown of a key neurosteroid-synthesizing enzyme directly affects an important function as nociception. Hopefully, these results may be useful for the development of novel analgesics.
authors.affiliation: Equipe Stéroïdes, Neuromodulateurs et Neuropathologies, Unité de Physiopathologie et Médecine Translationnelle, EA-4438, Université de Strasbourg, Bâtiment 3 de la Faculté de Médecine, 11 rue Humann, 67000 Strasbourg, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Patte-Mensah
authors.forename: Laurence
authors.initials: L
authors.lastname: Meyer
authors.forename: Véronique
authors.initials: V
authors.lastname: Schaeffer
authors.forename: Ayikoe G
authors.initials: AG
authors.lastname: Mensah-Nyagan
mesh_terms: D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific) / Q000378:metabolism*; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D005727:Ganglia, Spinal / Q000473:pathology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D006930:Hyperalgesia / Q000503:physiopathology; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D010146:Pain / Q000188:drug therapy / Q000209:etiology / Q000473:pathology*; D058748:Pain Perception / Q000187:drug effects; D017288:Pain Threshold / Q000502:physiology; D010523:Peripheral Nervous System Diseases / Q000150:complications; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D010812:Physical Stimulation / Q000379:methods; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013256:Steroids / Q000378:metabolism; D013997:Time Factors; D014316:Tritium / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013256:Steroids; D014316:Tritium; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D010751:Phosphopyruvate Hydratase