Early brain development has a tremendous impact on the success of humans throughout their lives. During early development, neural circuit formation proceeds in a strictly regulated manner. In addition to genetic and epigenetic programs, recent studies using animal models have demonstrated that certain maternal bio-active agents are essential for normal neural development, with deficiencies adversely affecting offspring brain function and behavior. On the basis of these findings, we propose a new viewpoint: that maternal bio-active substances support the development of the fetal and neonatal brain, and the subsequent expression and maintenance of higher brain functions. We term these molecular-based biological conversations between mother and offspring “bio-communications”. Based on findings obtained primarily from animal models, we review the effects of maternal substances on the neural developments and functions. Clarifying the regulatory mechanisms of “bio-communications” will help improve understanding of the mechanisms of human brain functioning and neural development. In addition, these findings will be applied to elucidate the mechanisms of developmental disorders and to explore new medical therapies to treat them.
In this review, we will summarize our ongoing studies on the functionality of both γ-aminobutyric acid (GABA) and glutamate receptors expressed by undifferentiated neural progenitor cells isolated from embryonic rodent brains. Cells were cultured with growth factors for the formation of round spheres by clustered cells under floating conditions, whereas a reverse transcription polymerase chain reaction analysis revealed expression of mRNA for particular subtypes of different ionotropic and metabotropic GABA and glutamate receptors in undifferentiated progenitors and neurospheres. Moreover, sustained exposure to either GABAergic or glutamatergic agonists not only modulated the size of neurospheres formed, but also affected spontaneous and induced differentiation of neural progenitor cells into particular progeny cell lineages such as neurons and astroglia. Both GABA and glutamate could play a pivotal role in the mechanisms underlying proliferation for self-replication along with the determination of subsequent differentiation fate toward particular progeny lineages through activation of their receptor subtypes functionally expressed by undifferentiated neural progenitor cells. Accordingly, neurogenesis seems to be also under control by GABAergic and glutamatergic signaling in developing brains as seen with neurotransmission in adult brains.
After the report of the Cardiac Arrhythmia Suppression Trial, a tabular framework of the Sicilian Gambit has been proposed to display actions of antiarrhythmic drugs on ion channels and receptors and to provide more rational pharmacotherapy of arrhythmias. However, because effects of antiarrhythmic drugs on If have not been thoroughly examined, we used patch clamp techniques to determine the effects of various antiarrhythmic drugs on the HCN (hyperpolarization-activated cyclic nucleotide–gated) channel currents. HCN4 channels, a dominant isoform of HCN channels in the heart, were expressed in HEK293 cells. Amiodarone and bepridil potently inhibited the HCN4 channel current with IC50 values of 4.5 and 4.9 μM, respectively, which were close to their therapeutic concentrations. The inhibitory effects of quinidine, disopyramide, cibenzoline, lidocaine, mexiletine, aprindine, propafenone, flecainide, propranolol, and verapamil on the HCN4 channel current were weak in their therapeutic concentrations, with IC50 values of 78.3, 249, 46.8, 276, 309, 43.7, 14.3, 1700, 50.5, and 44.9 μM, respectively, suggesting that the inhibitory effects on If would be clinically small. d,l-Sotalol hardly affected the HCN4 channel current. Information about the HCN4-channel effects of many antiarrhythmic drugs may be useful for determining the appropriate drug for treatment of various arrhythmias while minimizing adverse effects.
We previously reported that vascular endothelial functions in both retinal and systemic circulation are impaired 6 – 8 weeks after induction of hyperglycemia with streptozotocin (STZ) in rats. However, it remains to be elucidated whether the period required for the onset of endothelial dysfunction is different, depending on vascular beds and severity of hyperglycemia. In this study, we examined the effects of several vasodilators on the diameter of retinal blood vessel and blood pressure in Control, STZ (STZ treatment alone), and STZ + Glc (STZ treatment plus D-glucose feeding) rats. The overall structures of the retina and the retinal capillary network were also evaluated. The vasodilator effects of acetylcholine on retinal arterioles were significantly reduced in the STZ + Glc group, but not in the STZ group, 2 weeks after induction of hyperglycemia. There were no significant differences in acetylcholine-induced decreases in blood pressure among the three experimental groups. The responses to NOR3, forskolin, and adenosine were unaffected by hyperglycemia. The retinal thickness was significantly reduced in the STZ + Glc group. No significant changes were observed in the morphology and the density of retinal capillary network by immunohistochemical techniques. These results suggest that endothelium-dependent vasodilatory mechanisms of retinal arterioles are more vulnerable than those of peripheral resistance vessels to the effects of hyperglycemia. Hyperglycemia shortens the period required for onset of retinal endothelial dysfunction, depending on its severity.
Mouse colitis induced by transfer of CD4+CD45RBhigh CD25− cells share many pathological features with human inflammatory bowel disease (IBD). However, there is little known about how mouse colitis responds to drugs used for IBD treatment. To address this issue, we have investigated the effects of the IBD drugs, dexamethasone and anti-tumor necrosis factor-α antibody, on the mouse experimental colitis. Administration of either drug ameliorated their morbid signs such as body weight loss, colon shortening, and an increased ratio between colon and body weights (C/B ratio). Also improved were mucosal inflammatory signs in the colon, and histological damage scores were significantly decreased. Of the proinflammatory cytokines assayed in colon and plasma samples from the colitis mice, the colonic interleukin (IL)-1β level alone was significantly decreased by either drug administration. Regression analysis of data obtained with either drug revealed a close correlation between the histological damage score and C/B ratio or colonic IL-1β level. The present results show that the experimental mouse colitis responds to IBD drugs with its amelioration and that the C/B ratio and colonic IL-1β are available as a disease marker for IBD, suggesting the usefulness of this mouse model of colitis for pre-clinical screening of drug candidates for IBD treatment.
Phenotypic and contractile changes in pulmonary arterial smooth muscle cells (PASMCs) were examined in rats with pulmonary hypertension induced by hypoxia. Exposure to hypoxia induced pulmonary hypertension within 1 – 4 weeks. Staining with BrdU revealed that proliferative activities of PASMCs peaked at 1 week of hypoxic exposure, and then moderate proliferative activity was maintained for the next 2 – 4 weeks. The β-actin/α-actin ratio also increased at 1 – 2 weeks of exposure to hypoxia. Absolute contractility of the pulmonary arterial ring continuously decreased during hypoxia, whereas the basal active tonus of the pulmonary artery increased at 1 – 3 weeks. Nicardipine, the ETA-receptor antagonis, CI-1034 and the rho-kinase inhibitor Y27632 partially inhibited the elevated active tonus. Endothelin-1 content in the pulmonary hypertensive lung was continuously increased during exposure to hypoxia. In conclusion, the hypoxia-induced proliferative activity of PASMCs comprised a transient phase followed by a sustained phase. The change in PASMCs from a contractile to a synthetic phenotype also correlated with proliferative activity, which subsequently decreased PASMC contractility. The continuous production of endothelin-1 upon hypoxic exposure might contribute to the increased basal tonus of the pulmonary arterial wall, which might subsequently increase pulmonic arterial pressure, resulting in accelerated pulmonary hypertension.
DJ-1, a causative gene product of a familial form of Parkinson’s disease (PD), PARK7, plays a role in anti-oxidative stress, and loss of its function is thought to result in the onset of PD. Superfluous oxidation of cysteine at amino acid 106 (C106) of DJ-1 renders DJ-1 inactive, and such oxidized DJ-1 was observed in patients with the sporadic form of PD. In this study, we examined the relationship between DJ-1 and compounds extracted from traditional Chinese medicines possessing anti-oxidant activity. Of the 12 compounds tested, 5 were found to specifically bind to the C106 region by using a quartz crystal microbalance. Although 4 compounds prevented rat PC12 and primary neuronal cells from undergoing H2O2-induced cell death, the protective activity of 2 compounds, kaempferol 3-O-β-rutinoside and 6-hydroxykaempferol 3,6-di-O-β-D-glucoside, was diminished in cells transfected with siRNA targeting DJ-1, indicating DJ-1–dependent reaction of these compounds. Furthermore, these compounds reduced the level of reactive oxygen species and restored tyrosine hydroxylase activity that had been induced and compromised, respectively, by treatment of cells with H2O2. The results suggest that these compounds are useful lead compounds for PD therapy.
In a screening program aimed at discovering anti-osteoarthritis (OA) drugs, we identified an imidazo[5,1-c][1,4]thiazine derivative, ITZ-1, that suppressed both interleukin-1β (IL-1β)-induced proteoglycan and collagen release from bovine nasal cartilage in vitro and suppressed intra-articular infusion of IL-1β–induced cartilage proteoglycan degradation in rat knee joints. ITZ-1 did not inhibit enzyme activities of various matrix metalloproteinases (MMPs), which have pivotal roles in cartilage degradation, while it selectively inhibited IL-1β–induced production of MMP-13 in human articular chondrocytes (HAC). IL-1β–induced MMP production has been shown to be mediated by extracellular signal–regulated protein kinase (ERK), p38 kinase, and c-Jun N-terminal kinase (JNK) of the mitogen-activated protein kinase (MAPK) family signal transduction molecules. An ERK–MAPK pathway inhibitor (U0126), but not a p38 kinase inhibitor (SB203580) or a JNK inhibitor (SP600125), also selectively inhibited IL-1β–induced MMP-13 production in HAC. Furthermore, ITZ-1 selectively inhibited IL-1β–induced ERK activation without affecting p38 kinase and JNK activation, which may account for its selective inhibition of MMP-13 production. Inhibition of nitric oxide (NO)-induced chondrocyte apoptosis has been another area of interest as a therapeutic strategy for OA, and ITZ-1 also suppressed NO-induced death in HAC. These results suggest that ITZ-1 is a promising lead compound for a disease modifying anti-OA drug program.
Only a few experimental studies have demonstrated the effectiveness of some cyclooxygenase-2 (COX-2) inhibitors for neuropathic pain in diabetic animals. In this study we investigated the usefulness of one such COX-2 inhibitor, meloxicam, for treatment of established diabetic neuropathic pain in mice. Intraperitoneal and perineural injection, but not intrathecal injection, of meloxicam elevated the lowered threshold in the von Frey test. These results suggest that meloxicam exerts antiallodynic effects on established neuropathic pain in diabetic mice, and that the site of its action is peripheral. Meloxicam may therefore be a potentially useful drug for treatment of diabetic neuropathic pain.
The involvement of Ca2+ entry via the Na+/Ca2+ exchanger (NCX) in myogenic constriction of rat posterior cerebral arteries was investigated. RT-PCR identified mRNA for NCX1, 2, and 3 in the arteries. Na+ removal increased [Ca2+]i, which was reduced by the NCX inhibitor SEA0400. SEA0400 inhibited the development, but not the steady-state, of pressure-induced myogenic constriction, whereas it decreased both the initial and sustained phases of [Ca2+]i elevation. These results suggest that Ca2+ entry via NCX is involved in the development, but not the steady-state, of pressure-induced myogenic constriction.
We have recently shown that gabapentin generates protein kinase A (PKA)-dependent presynaptic inhibition of GABAergic synaptic transmission in locus coeruleus (LC) neurons only under neuropathic states. To verify behaviorally this in vitro electrophysiological finding, the PKA inhibitor H-89 was injected intracerebroventricularly (i.c.v.) before supraspinal application of gabapentin in mice developing thermal and mechanical hypersensitivity after peripheral nerve injury. H-89 dose-dependently attenuated the analgesic effects of i.c.v.-injected gabapentin, suggesting that PKA-dependent removal of GABAergic inhibition of LC neurons is the most plausible synaptic mechanism underlying the supraspinally mediated analgesic effects of gabapentin involving activation of the descending noradrenergic pain-inhibitory system.
The aim of this study was to establish a method for evaluating gastrocecal transit time using a simple and noninvasive 13C breath-test system in conscious rats. After fasting, rats were orally administered lactose-[13C]ureide. 13CO2 level in the expired air was measured at appropriate intervals. It was confirmed that priming dose of lactose-ureide was necessary for determining gastrocecal transit time. The level of 13CO2 in the expired air increased in a lactose-[13C]ureide dose–dependent manner. The gastrocecal transit time determined with 30 mg/kg of lactose-[13C]ureide was 160 ± 24.5 min. This method is expected to contribute to the further understanding of intestinal pathophysiology.