The semaphorin family comprises secreted and transmembrane signaling proteins that function in the nervous, immune, respiratory and cardiovascular systems.Sema3A, a secreted type of semaphorin, is now recognized as the most potent repulsive molecule inhibiting or repelling neurite outgrowth.The biological actions of Sema3A are mediated via neuropilin(Npn)-1, a receptor or one of the components of a receptor complex for Sema3A.Although the molecular mechanisms of Sema3A-Npn-1 signaling are largely unknown, a pertussis toxin-sensitive trimeric G protein(s), Rac-1, collapsin response mediator protein(CRMP), cyclic nucleotides and tyrosine kinase(s) have been implicated as essential and/or modulatory components of these processes.As repulsive molecules could be impediments to axon outgrowth, determining how these repulsive molecules exert their actions has the potential of uncovering new therapeutic approaches to injury and/or degeneration of neuronal tissues.
The clinical potential of gene transfer is increasing.One likely major application of this emerging biotechnology will be for gene therapeutics, the use of a gene as a drug.Salivary glands provide an unusual but increasingly valuable target site for gene transfer.Studies in animal salivary glands from several laboratories, including our own, have provided proof of this concept.In this review, we provide a background and perspective on possible strategies for gene-based immunopharmacology in salivary glands.We use as a target disease model the autoimmune exocrinopathy Sjögren’s syndrome.
The effects of lipid mediator antagonists:the LTD4-receptor antagonist pranlukast, the TXA2-receptor antagonist seratrodast, and the novel dual LTD4- and TXA2-receptor antagonist YM158(3-[(4-tert-butylthiazol-2-yl)methoxy]-5′-[3-(4-chlorobenzenesulfonyl)propyl]-2′-(1H-tetrazol-5-ylmethoxy)benzanilide monosodium salt monohydrate)were investigated in animals exhibiting immediate asthmatic response(IAR), late asthmatic response(LAR)and airway hyper-responsiveness(AHR).Antigen-induced LAR and AHR are inhibited by orally administered pranlukast(30, 100mg/kg) and seratrodast(3, 10mg/kg).YM158(30mg/kg), orally administered before or after IAR induction, also inhibited both LAR and AHR.However, while the inhibitory effects of pranlukast and seratrodast on IAR were marginal, the effects of YM158(3, 10, 30mg/kg) were dose-dependent, probably due to its multiple sites of action.Additionally, orally administered YM158(30mg/kg) inhibited ozone-induced AHR in guinea pigs.Thus, an antagonist that inhibits several lipid mediators might exhibit greater efficacy in treating asthmatic responses than antagonists with a single site of action.Therefore, YM158 shows great promise as a drug that will be able to treat bronchial asthma and related disorders more potently than currently used single-pathway inhibitors.
Although 3-acetylpyridine(3-AP) induces several motor disturbances and it degenerates the olivocerebellar pathway, abnormalities caused by 3-AP in cerebral motor regions remain to be elucidated.Here we investigated the metabolic changes caused by 3-AP(75mg/kg, i.p.) on local cerebral glucose utilization(LCGU) in various brain regions.The effects of anti-ataxic agents, thyrotropin-releasing hormone(TRH)(10mg/kg, i.p.) and its mimetic agent taltirelin hydrate(1mg/kg, i.p.), on the 3-AP-induced change in LCGU were also investigated.The LCGU in the nuclei of the basal ganglia, thalamus, limbic structures and brainstem of 3-AP-treated rats was significantly lower than that of naive animals.However 3-AP increased the LCGU of the cerebellar nuclei.TRH restored depressed LCGU in the substantia nigra and ventral tegmental area.TRH tended to restore the lowered LCGU in several nuclei of 3-AP-treated rats.Moreover, taltirelin further increased the LCGU in the cerebellar nuclei.These results suggest that the motor disturbance of the 3-AP-treated rats may be due to not only degeneration of the olivocerebellar pathway but also dysfunction of the several areas that play a role in motor coordination.Moreover, the anti-ataxic action by TRH could result from metabolic restoration of the multiple motor-coordination-related areas.
Neurotoxicity of β42(20μM) in cultured rat hippocampal neurons was evaluated by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide(MTT) reduction and lactate dehydrogenase(LDH) release methods as quantitative assays of cell death, and both methods indicated that propentofylline(PPF) had the ability to protect the neurons against the toxicity, although these two assay methods revealed different mechanisms for the toxic effect of β42.Promotion of the active exocytotic system of the cells was suggested after treatment with β42 in the MTT assay and in determination of 9-aminoacridine(AA) excretion from the preloaded cells after 24-h treatment with β42.The promotion of AA exocytosis was blocked by the addition of PPF(20μg/ml).The preventive effect of PPF on the neurotoxicity of β42 has been proposed to be caused by elevation of the intracellular level of cAMP as a result of depression of the hydrolytic activity of cells.
We investigated the effects of ABT-627, a selective ETA-receptor antagonist, and A-192621, a selective ETB-receptor antagonist, on ischemic acute renal failure(ARF)in rats.Ischemic ARF was induced by clamping the left renal artery and vein for 45min, 2 weeks after the contralateral nephrectomy.Renal function in untreated ARF rats markedly decreased at 24h after reperfusion and thereafter tended to recover gradually.ABT-627(1mg/kg, i.v.)administration before ischemia markedly attenuated the renal dysfunction induced by the ischemia/reperfusion, whereas A-192621(3mg/kg, i.v.)pretreatment was without effect.Histopathological examination of the kidney of untreated ARF rats revealed severe renal damage such as tubular necrosis, proteinaceous casts in tubuli and medullary congestion.Histologically evident damage was improved by pretreatment with ABT-627, but not with A-192621.Daily oral administration of ABT-627(10mg/kg per day), but not A-192621(30mg/kg per day), given after the ischemia/reperfusion period also exerted protective effects.These findings clearly indicate that endothelin, acting via the ETA receptor, participates in the pathogenesis of ischemic ARF.Thus, selective ETA-receptor antagonism may be useful in the treatment of human ischemic ARF, whereas selective blockade of the ETB receptor will probably be ineffective.
We studied the mechanisms and characteristics of the spontaneously evoked intracellular Ca2+ changes(Ca2+ oscillations)in ileal longitudinal smooth muscle from guinea pig.Two-dimensional images of Ca2+ oscillations were obtained at 33-ms intervals with a Ca2+-sensitive fluorescence probe, fluo-3 using the intensified CCD camera.Nicardipine(10-7M)significantly decreased the maximum level of fluorescence intensity of the Ca2+ oscillations, inhibited the frequency of the oscillations and tended to decrease the basal level of fluorescence intensity.However, tetrodotoxin(3×10-7M)did not affect these oscillations.Phorbol 12, 13-dibutyrate(10-7M)significantly increased the maximum level of fluorescence intensity and the frequency of Ca2+ oscillations, and it changed them to steady and chronometric Ca2+ oscillations.Cyclopiazonic acid(3×10-5M)also significantly increased the frequency of Ca2+ oscillations.Acetylcholine(10-8M)increased the basal and maximum level of fluorescence intensity and the frequency of Ca2+ oscillations, and accelerated their onset.The increase of basal level of fluorescence intensity was then decreased by cyclopiazonic acid treatment.These results suggest that the augmentation of Ca2+ oscillations is mainly due to the activation of L-type Ca2+ channels, which is modulated by protein kinase C, and that the emptying of intracellular Ca2+ stores may activate the Ca2+ oscillations mediated through the increase of Ca2+ influx in ileal smooth muscle of guinea pig.
Low molecular weight, heparin(LMWH)possesses multiple nonanticoagulant properties.In the present study, we observed its anti-airway allergic inflammatory effects by bronchoalveolar lavage in guinea pigs.Guinea pigs were sensitized by repeatedly inhaling aerosolized ovalbumin.LMWH(400u/l, 800u/l), dexamethasone(1.2mg/l)or vehicle(normal saline)was inhaled for 7 days.Then the animals were sacrificed under anesthesia and then lavaged with ice-cold Hank’s buffer immediately;bronchoalveolar lavage fluid(BALF)was prepared 24h afterr the animals were challenged by antigen exposure.The effects of LMWH on total cell counts, absolute eosinophil counts and cell catalogues in BALF were studied;effects on the activity of eosinophil peroxidase(EPO)and the contents of histamine and eosinophil cationic protein(ECP)in BALF supernatant were detected.Our results showed that compared with the vehicle group, LMWH at 400u/l and 800u/l could significantly reduce total cell counts, absolute eosinophil counts and percentage of eosinophils in BALF(P<0.05 and P<0.01, respectively);LMWH at 800u/l markedly inhibited the activity of EPO in BALF supernatant(P<0.05);LMWH at 400u/l and 800u/l remarkably reduced the content of histamine in BALF supernatant(P<0.05 and P<0.01, respectively), LMWH at 800u/l decreased the content of ECP(P<0.05)significantly.It suggested that LMWH exerted anti-airway allergic inflammatory action by inhibiting infiltration of inflammatory cells and reducing release of inflammatory mediators, as well as antagonizing their activities, and that LMWH could be developed as a potential anti-bronchial asthmatic drug.
Muscarinic receptor subtypes controlling the nonselective cationic current in response to carbachol(ICCh)were studied in circular smooth muscle cells of the guinea pig gastric antrum using putative muscarinic agonists and antagonists.Both oxotremorine-M(an M2-selective agonist)and CCh dose-dependently activated the cationic current with EC50 values of 0.21±0.01μm and 0.97±0.06μM, respectively.In contrast, pilocarpine and McN-A 343(an M1-selective and a putative M4 agonist)were weak partial agonists.In response to 10μM CCh, 4-DAMP, methoctramine and pirenzepine dose-dependently inhibited ICCh and had IC50 values of 1.91±0.2nM, 0.46±0.07μM and 8.33±0.4μM, respectively.4-DAMP, methoctramine and pirenzepine shifted the concentration-response curves of ICCh to the right without significantly reducing the maximal current.Values of the apparent dissociation constant pA2 obtained from Schild plot analysis were 9.24, 7.72 and 6.62 for 4-DAMP, methoctramine and pirenzepine, respectively.Also, pertussis toxin completely blocked ICCh generation.These results suggest that the M2-subtype plays a crucial role in the activation of the ICCh, and a block of the M3-subtype reduces the sensitivity of the M2-mediated response with no significant reduction of maximum response.
Recent studies have indicated that sphingosine 1-phosphate(Sph-1-P)is released into the blood flow from activated platelets upon stimulation to exhibit a wide spectrum of biological functions.The purpose of the present study was to assess the acute cardiovascular effects of circulating Sph-1-P in the in vivo rat model.Intravenous administration of Sph-1-P decreased the heart rate, ventricular contraction and blood pressure, while it hardly affected the atrioventricular and intraventricular conduction.Sph-1-P did not affect the adenylate cyclase activities of the membrane preparations made from the right atrium and left ventricle.These results suggest that functional receptors like lysophospholipid receptor Edg-1, which can inhibit adenylate cyclase via Gi protein, are lacking in the rat heart.Moreover, these observations will provide a clue to better understand the various types of Sph-1-P-related pathophysiological processes.
It is known that mu-agonists inhibit electrical field stimulation(EFS)-evoked ACh release from longitudinal muscle myenteric plexus(LMMP)preparation of guinea pig ileum when muscarinic autoinhibition does not fully work.In the present study, the possible role of K+ channels in the mechanisms of mu-agonists-induced inhibition and autoinhibition of ACh release was studied.In the presence of atropine, which blocks the autoinhibition, non-selective K+ channel blockers, tetraethylammonium(TEA)and 4-amino-pyridine(4-AP), reversed the inhibitory effect of mu-agonists, morphine and [D-Ala2, N-Me-Phe4, Gly5-ol]enkephalin, on EFS-evoked ACh release, but not that of kappa-agonist U-50, 488.Apamin, iberiotoxin or glibenclamide did not affect the inhibition of ACh release by morphine.On the other hand, in the absence of atropine(under the autoinhibition working condition), 4-AP increased EFS-evoked ACh release, but atropine did not further increase ACh release in the presence of 4-AP.In contrast, although TEA did not affect EFS-evoked ACh release, atropine increased ACh release in the presence of TEA.These results suggest that the inhibitory effects of mu-agonists and muscarinic autoinhibition on the ACh release are associated with activation of different types of K+ channels in the guinea pig LMMP preparations:the former is associated with 4-AP- and TEA-sensitive K+ channels and the latter is associated with 4-AP- but not TEA-sensitive K+ channels.
The effect of zaldaride, a calmodulin inhibitor, on fecal pellet output in rats was compared with that of loperamide, an antidiarrheal drug.5-Hydroxytryptamine(10mg/kg, s.c.), neostigmine(0.3mg/kg, s.c.)and nicotine(1.0mg/kg, s.c.)increased fecal pellet output.Zaldaride(≥30mg/kg, p.o.)reduced these increases in facal pellet outputs.Loperamide(10mg/kg, p.o.)inhibited fecal pellet output induced by 5-hydroxytryptamine and neostigmine but not nicotine.Under normal conditions, zaldaride and loperamide did not affect fecal pellet output at doses used in these studies.In conclusion, zaldaride may inhibit increases in fecal pellet output induced by hyperpropulsion of the gastrointestinal tract without causing constipation as a side effect.
To identify the NMDA receptor-mediated mechanism in augmenting expiratory(E2)neurons, the effects of systemic and local application of dizocilpine on spontaneous and evoked postsynaptic potentials(PSPs)were investigated in decerebrate and vagotomized cats.Intravenously applied dizocilpine reduced the inhibitory PSPs during inspiration and stage 1 expiration, but had little effect on the excitatory PSPs during stage 2 expiration.Iontophoresed dizocilpine caused a continuous hyperpolarization throughout the respiratory cycle.Dizocilpine had no effect on vagally evoked PSPs.These results suggest that the NMDA mechanisms are involved presynaptically in periodic postsynaptic inhibitions and postsynaptically in tonic excitation in E2 neurons.