Epigenetics is a mechanism that regulates gene expression not depending on the underlying DNA sequence, but on the chemical modifications of DNA and histone proteins. Defects in the factors involved in epigenetic regulation cause congenital neurodevelopmental diseases, and thus, epigenetic regulation is essential for normal brain development. Besides these intrinsic defects, it is becoming increasingly apparent that extrinsic factors, such as insufficient nutrition, psychiatric drugs, and mental stress, also alter epigenetic regulation. Therefore, environmental factors may lead to “acquired” neurodevelopmental disorders through the failure of epigenetic regulation. Epigenetics is a biological key to understand the gene–environment interactions in neurodevelopmental disorders. As the mechanism is reversible, its comprehensive understanding will result in the development of new therapies for these disorders.
The motor neurons of patients with sporadic amyotrophic lateral sclerosis (ALS) express abundant Q/R site–unedited GluR2 mRNA, whereas those of patients with other motor neuron diseases including familial ALS associated with mutated SOD1 (ALS1) and those of normal subjects express only Q/R site–edited GluR2 mRNA. Because adenosine deaminase acting on RNA type 2 (ADAR2) specifically catalyzes GluR2 Q/R site–editing, it is likely that ADAR2 activity is not sufficient to edit this site completely in motor neurons of patients with sporadic ALS. Because these molecular abnormalities occur in disease- and motor neuron–specific fashion and induce fatal epilepsy in mice, we have hypothesized that GluR2 Q/R site–underediting due to ADAR2 underactivity is a cause of neuronal death in sporadic ALS. We found that cytoplasmic fragile X mental retardation protein interacting protein 2 (CYFIP2) mRNA had an ADAR2-mediated editing position using RNA interference knockdown. Our review will include a discussion of new ADAR2 substrates that may be useful for research on sporadic ALS.
Febrile seizures (FS) are the most common type of convulsive events in infancy and childhood. Genetic and environmental elements have been suggested to contribute to FS. FS can be divided into simple and complex types, the former being benign, whereas it is controversial whether complex FS have an association with the development of temporal lobe epilepsy (TLE) in later life. In the hippocampus of TLE patients, several structural and functional alterations take place that render the region an epileptic foci. Thus, it is important to clarify the cellular and molecular changes in the hippocampus after FS and to determine whether they are epileptogenic. To achieve this goal, human studies are too limited because the sample tissues are only available from adult patients in the advanced and drug-resistant stages of the disease, masking the underlying etiology. These facts have inspired researchers to take advantage of well-established animal models of FS to answer the following questions: 1) How does hyperthermia induce FS? 2) Do FS induce neuroanatomical changes? 3) Do FS induce neurophysiological changes? 4) Do FS affect the behavior in later life? Here we introduce and discuss accumulating reports to answer these questions.
Degeneration of the lumbar spine plays an important role in most chronic low back pain. Prevention of lumbar intervertebral disc (IVD) degeneration is therefore a high research priority. Both our previous multicenter clinical trials and pharmacological research showed that Fufangqishe-Pill (FFQSP), a newly patented traditional Chinese medicine, could effectively relieve the symptoms of neck pain and prevent cervical degeneration. To clarify the effect of FFQSP on lumbar IVD degeneration, we applied a lumbar IVD degeneration rat model induced by prolonged upright posture. Pretreatment of FFQSP for one month prevented the histological changes indicating IVD disorganization; increased type II–collagen level, decreased type X–collagen protein level, and increased Col2α1 mRNA expression at all time points; and decreased Col10α1, matrix metalloproteinase (MMP)-3, MMP13, and Interleukin (IL)-1β mRNA expression induced by upright posture for 7 and 9 months. These results suggest that FFQSP prevents lumbar IVD degeneration induced by upright posture. FFQSP is a promising medicine for lumbar IVD degeneration disease.
Altered S-nitrosothiols (RSNO) signaling is linked to pulmonary hypertension. Recent studies have shown that S-nitrosoglutathione (GSNO) reductase (GSNOR) catalyzes the degradation of GSNO and indirectly regulates the level of RSNO in vivo. Our present study tested the hypothesis that chronic hypoxia causes pulmonary hypertension, in part, by the change of GSNOR activity that contributes to the depletion of RSNO. Male mice were exposed to normobaric hypoxia in a ventilated chamber for 1 to 21 days or normoxia for 21 days. Right ventricular systolic pressure, right ventricle hypertrophy, and the number and media thickness of muscular pulmonary vessels increased significantly after 21 days of hypoxic exposure. Hypoxia induced the overexpression of endothelial nitric oxide synthase and inducible nitric oxide synthase. The mRNA expression of GSNOR decreased on day 1 of hypoxic exposure, but increased significantly on day 7 compared with the normoxic group. The protein expression of GSNOR increased significantly in the lung tissue after 7 days of hypoxic exposure and its enzymatic activities also increased. Both the ratios of glutathione to glutathione disulfide and nitrate to nitrite were significantly lower in the hypoxic groups than in the normoxic controls. The results suggest an increased GSNOR activity interfered with the metabolism of RSNO in mice with hypoxic pulmonary hypertension. An imbalanced of redox status is associated with the pathogenesis of hypoxic pulmonary hypertension.
This study was performed to investigate the ameliorative effects of metabotropic glutamate (mGlu)-receptor agonists on histamine H1 receptor antagonist–induced spatial memory deficit and the decrease in hippocampal theta activity in rats. Intraperitoneal injection of pyrilamine (35 mg/kg) resulted in impaired reference and working memory in the radial maze task and decreased hippocampal theta amplitude and power. The working memory deficit and decreased hippocampal theta power induced by pyrilamine were ameliorated by intrahippocampal injection of (RS)-3,5-dihydroxyphenylglycine (DHPG) (1 and 10 μg/side), a group I mGlu-receptor agonist; however, intrahippocampal injection of (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (APDC), a group II mGlu-receptor agonist, and L-(+)-2-amino-4-phosphonobutyric acid (L-AP4), a group III mGlu-receptor agonist, showed no significant effect on the pyrilamine-induced memory deficit and decreased hippocampal theta activity. These results indicate that the activation of hippocampal group Ι mGlu receptors, but not group II and III mGlu receptors, improve the histamine H1 receptor antagonist–induced working memory deficit and decreased hippocampal theta activity.
Hepatoprotectant silibinin has anticancer and chemo-preventive effects. In this study, silibinin showed significant inhibitory effect on human fibroblast HT 1080 cell growth cultured in media containing 10% fetal bovine serum or in serum free media, and in the latter case, silibinin exerted a more significant effect. Silibinin induced autophagy at 12 h, confirmed by monodansylcadervarine (MDC) staining, up-regulation of Beclin 1 (initiation factor for autophagosome formation), and conversion of LC3 I to LC3 II (autophagosome marker). It also induced apoptosis at 24 h, proved by observation of apoptotic body and activation of caspase-3. 3-Methyladenine (3-MA) inhibited silibinin-induced autophagy and promoted cell survival, suggesting that autophagy enhanced silibinin-induced apoptosis in HT1080 cells. Silibinin generated reactive oxygen species (ROS) in HT1080 cells, and the ROS scavenger N-acetylcysteine (NAC) reversed the cytotoxicity of silibinin, resulting in cell survival by inhibition of autophagic and apoptotic pathways. Application of specific antioxidants demonstrated that H2O2 was a major factor in silibinin-induced ROS since the H2O2 scavenger catalase reduced both autophagy and cell death. O2•− also contributed to silibinin-induced cell death.
The present study was designed to examine the binding affinity and functional potency of selective angiotensin II type 1 (AT1)-receptor antagonists towards specific mutants of AT1 receptor using site-directed mutagenesis. We also compared our results with the wild-type AT1 receptor and investigated the possible reasons behind that. Both wild-type and mutant receptors were expressed in COS-7 cells and the binding affinities of the antagonists were determined by radioligand binding assay. Inhibition of agonist-stimulated inositol phosphate accumulation by the antagonists was also done. Substitution of asparagine235 of intracellular loop 3 of the AT1 receptor by arginine increased the binding affinity of the antagonists 5 – 34-fold, whereas the increase in the binding affinity of the antagonists in the phenylalanine239 mutant by arginine and tryptophan (F239R and F239W) were 3 – 19-fold and 2 – 15-fold higher, respectively, compared to the wild-type AT1 receptor. The results suggested that substitution by a positively charged or sterically hindered amino acid in the AT1 receptor allows it to interact with the acidic tetrazole moiety and carboxylate groups of the antagonists more strongly compared to the wild-type receptor. These findings may play an important role to change the binding affinity of the antagonists to an effective level for the pharmacological function of the drugs.
Tamoxifen inhibits transmembrane currents of the Kir2.x inward rectifier potassium channels by interfering with the interaction of the channels with membrane phosphatidylinositol 4,5-bisphosphate (PIP2). We tested the hypothesis that Kir channels with low affinity for PIP2, like the adenosine triphosphate (ATP)-sensitive K+ channel (KATP) and acetylcholine (ACh)-activated K+ channel (KACh), have at least the same sensitivity to tamoxifen as Kir2.3. We investigated the effects of tamoxifen (0.1 – 10 μM) on Kir6.2/SUR2A (KATP) and Kir3.1/3.4 (KACh) channels expressed in HEK-293 cells and ATP-sensitive K+ current (IKATP) and ACh-activated K+ current (IKACh) in feline atrial myocytes. The onset of tamoxifen inhibition of both IKATP and IKACh was slow (T1/2 approximately 3.5 min) and concentration-dependent but voltage-independent. The time course and degree of inhibition was independent of external or internal drug application. Tamoxifen interacts with the pore forming subunit, Kir6.2, rather than with the SUR subunit. The inhibitory potency of tamoxifen on the Kir6.2/SUR2A channel was decreased by the mutation (C166S) on Kir6.2 and in the continuous presence of PIP2. In atrial myocytes, the mechanism and potency of the effects of tamoxifen on KATP and KACh channels were comparable to those in HEK-293 cells. These data suggest that, similar to its effects on Kir2.x currents, tamoxifen inhibits KATP and KACh currents by interfering with the interaction between the channel and PIP2.
We have previously indicated that glycyrrhizin (GL), a major component of licorice, has glucocorticoid-like anti-inflammatory effects in cultured airway epithelial cells and suggested its usefulness in the treatment of inflammatory respiratory diseases. On the other hand, mucus hypersecretion in the respiratory tract and goblet cell hyperplasia in the airway epithelium contribute to the morbidity and mortality associated with airway inflammatory diseases. This study, therefore, aimed to examine the effects of GL on airway mucus hyperproduction and define the mechanisms behind these effects. In an in vivo model, GL significantly attenuated goblet cell hyperplasia and MUC5AC mRNA expression in mice treated with lipopolysaccharide or interleukin-4. In addition, GL significantly attenuated MUC5AC protein and mRNA expression by tumor growth factor (TGF)-α in cultured NCI-H292 cells. GL also attenuated TGF-α–stimulated MUC5AC promoter activity in a luciferase reporter gene assay, but did not affect the stability of MUC5AC mRNA. Taken together, we concluded that GL has an inhibitory effect on mucus hyperproduction both in vivo and in vitro and that GL-mediated inhibition may be mediated through the inhibition of MUC5AC gene transcription. [Supplementary Figures: available only at http://dx.doi.org/10.1254/jphs.09344FP]
Localization of cyclooxygenase-2 (COX-2) in rat aortae was investigated. In endothelium-intact aortic strips stimulated with interleukin-1β (IL-1β), COX-2 was detected in adventitial fibroblasts and macrophages but not in tunica media. IL-1β−induced COX-2 expression was also detected in medial smooth muscle cells of endothelium-denuded aortae and cultured rat aortic smooth muscle cells. IL-1β−induced COX-2 expression in all of the above cells was abolished in the presence of U0126, an inhibitor of extracellular signal-regulated kinases (ERK). Thus, IL-1β induces COX-2 through the ERK-mediated pathway in adventitial fibroblasts and macrophages of healthy aortae; and in addition, medial smooth muscle cells are also responsible for COX-2 expression in remodeled aortae.
The chemoattractant receptor–homologous molecule expressed on T-helper type 2 cells (CRTH2) is the most recently identified prostaglandin (PG) receptor for both PGD2 and 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2). We examined the mechanism by which 15d-PGJ2 enhances nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells. CAY10471 (CRTH2 antagonist) inhibited both the neurite-promotion and p38 mitogen-activated protein (MAP) kinase phosphorylation induced by 15d-PGJ2. In contrast, 13,14-dihydro-15-keto-PGD2 (DK-PGD2) (selective CRTH2 agonist) stimulated its phosphorylation but failed to produce neurite-promoting effects. These suggest, for the first time, the action of 15d-PGJ2 is mediated by CRTH2, although the CRTH2 activation alone is insufficient for the underlying action.
The contribution of Cl− conductance relative to that of K+ in the regulation of membrane potential was examined using OUMS-27 cells, a model cell-line of human chondrocytes. Application of 100 μM niflumic acid (NFA) and other anion-channel blockers induced significant membrane hyperpolarization. The NFA-sensitive membrane current under voltage-clamp was predominantly Cl− current. Application of NFA induced small but significant increase in intracellular Ca2+ concentration ([Ca2+]i) and markedly enhanced the late component of [Ca2+]i rise induced by 1 μM histamine. In conclusion, Cl− conductance substantially contributes to the regulation of resting membrane potential and [Ca2+]i in OUMS-27 cells.