Dorsal root ganglion neurons express a wide repertoire of sodium channels with different properties. Here, we report the cloning
from rat, dorsal root ganglia (DRG), cellular expression, and ...functional analysis of a novel tetrodotoxin-sensitive peripheral
sodium channel (PN), PN1. PN1 mRNA is expressed in many different tissues. Within the rat DRG, both the mRNA and PN1-like
immunoreactivity are present in small and large neurons. The abundance of sodium channel mRNAs in rat DRG is rBI > PN1 ⥠PN3
>>> rBIII by quantitative reverse transcription-polymerase chain reaction analysis. Data from reverse transcription-polymerase
chain reaction and sequence analyses of human DRG and other human tissues suggest that rat PN1 is an ortholog of the human
neuroendocrine channel. In Xenopus oocytes, PN1 exhibits kinetics that are similar to rBIIa sodium currents and is inhibited by tetrodotoxin with an IC 50 of 4.3 ± 0.92 n m . Unlike rBIIa, the inactivation kinetics of PN1 are not accelerated by the coexpression of the β-subunits.
Neuropathic pain may be produced, at least in part, by the increased activity of primary afferent neurons. Studies have suggested that an accumulation of voltage-gated sodium channels at the site of ...peripheral nerve injury is a primary precursory event for subsequent afferent hyperexcitability. In this study, a human sodium channel (hPN3, SCN10A) has been cloned from the lumbar 4/5 dorsal root ganglia (DRG). Expression of hPN3 in Xenopus oocytes showed that this clone is a functional voltage-gated sodium channel. The amino acid sequence of hPN3 is most closely related to the rat PN3/SNS sodium channels which are expressed primarily in the small neurons of rat DRGs. The homologous relationship between rPN3 and hPN3 is defined by (i) a high level of sequence identity (ii) sodium currents that are highly resistant to tetrodotoxin (TTX) (iii) similar tissue distribution profiles and (iv) orthologous chromosomal map positions. Since rPN3/SNS has been implicated in nociceptive transmission, hPN3 may prove to be a valuable target for therapeutic agents against neuropathic pain.
Some antioxidants, including butylated hydroxyanisole (BHA), tetrahydropapaveroline (THP), nordihydroguiauretic acid, and 10,11-dihydroxyaporphine (DHA), were found to be potent inhibitors of the ...production of tumor necrosis factor (TNF)-alpha, IL-1 beta, and IL-6 by human peripheral blood mononuclear cells (PBMC) stimulated by lipopolysaccharide (LPS) (IC50s in the low micromolar range). Inhibition of cytokine production was gene selective and not due to general effects on protein synthesis. Inhibition of cytokine production by PBMC was observed also when other inducers were used (staphylococci, silica, zymosan). Much higher concentrations of other antioxidants--including ascorbic acid, trolox, alpha-tocopherol, butylated hydroxytoluene, and the 5-lipoxygenase inhibitor zileuton--did not affect the production of these cytokines. The active compounds did not inhibit IL-1-induced production of IL-6 in fibroblasts, showing the cell selectivity of the effect. Antioxidant-mediated inhibition of cytokine production was correlated with low levels of the corresponding messenger RNAs. Nuclear run-on experiments showed that THP inhibited transcription of the IL-1 beta gene. THP decreased the concentration of the transcription factors NF-kappa B and AP-1 detected in nuclear extracts of PBMC cultured in the presence or absence of LPS. THP and DHA markedly decreased the levels of TNF-alpha and IL-1 beta in the circulation of mice following LPS injection. Thus antioxidants vary widely in potency as inhibitors of the activation of transcription factors and of the transcription of genes for pro-inflammatory cytokines. Coordinate inhibition of the transcription of genes for inflammatory cytokines could provide a strategy for therapy of diseases with inflammatory pathogenesis and for septic shock.
Interleukin-1 (IL-1) and transforming growth factorα (TGFα) mRNA expression was analyzed in cultured normal human keratinocytes. Keratinocytes constititively express IL-1 mRNA when cultured in ...keratinocyte growth medium but not in Dulbecco's minimal essential medium containing fetal bovine serum, in which the cells differentiate. The pre- dominant form of IL-1 expressed by keratinocytes is IL-1α. Addition of IL-1α to keratinocytes increased IL-1α and TGFα mRNA expression in a dose-dependent manner. TGFα induced a similar increase in IL-1α and TGFα mRNA in keratinocytes. Hydrocortisone decreased the expression of both IL-1α and TGFα mRNA in keratinocytes. These findings document an autocrine mechanism by which IL-1α and TGFα can stimulate the proliferation of keratinocytes in the skin. It is proposed that this autocrine loop may be hyperactive in psoriasis. Antagonism of the effects of this autocrine loop may be one of the mechanisms by which glucocorticoids exert clinically useful effects in psoriasis and other diseases of the skin.
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