[Prickle planar cell polarity protein 1 involved in the pathogenesis of skeletal class Ⅲ malocclusion]

Objective: To explore the mechanisms of prickle planar cell polarity protein 1 (PRICKLE1) involved in the occurrence of skeletal Class Ⅲ malocclusion. Methods: After extracting the genomic DNA of all family members of the skeletal Class Ⅲ malocclusion pedigree with maxillary hypoplasia collected in the Department of Orthodontics at the Affiliated Stomatological Hospital of Nanjing Medical University in October 2021, whole exome sequencing and Sanger sequencing were performed to screen pathogenic genes/mutation sites and validate the mutations. Jaw tissue was collected during the operation of orthognathic patients who were treated in the Department of Oral and Maxillofacial Surgery at the same hospital from October 2021 to December 2022. Following the extraction of human jaw bone marrow mesenchymal stem cells and transfection with overexpressing lentivirus (lentiviruses overexpressing the gene of interest served as the wild group, lentiviruses overexpressing mutation site served as the mutant group) and knockdown lentivirus (divided into knockdown group 1 and 2, with transfection interference negative lentiviruses as the control group). Various assays including real-time fluorescence quantitative PCR (RT-qPCR), Western blotting, proliferation and Transwell assays, alkaline phosphatase staining and alizarin red staining were performed. Construction of zebrafish animal model, morpholino oligonucleotide (MO) were injected to knock down the expression of prickle1a and prickle1b in zebrafish (co-knocking group), and the control group was injected with standardized MO as a reference. Transcriptome sequencing, enrichment analysis and co-expression analysis were performed on the zebrafish craniofacial tissues of the two groups. Results: Two patients of this family carried this mutation PRICKLE1 c.113C>T. The transfection experiments showed that compared with the wild group (relative expression of PRICKLE1 was 21.97±0.60), the relative expression of mutant group (5.05±0.05) was significantly reduced (P<0.05), and cell proliferation and migration ability significantly enhanced (P<0.05), and osteogenic differentiation ability was significantly reduced (P<0.05). Compared with the control group, the proliferation and migration ability of cells in the two knockdown groups were significantly enhanced (P<0.05), and the osteogenic differentiation ability was significantly reduced (P<0.05). Zebrafish model experiments showed the width of the ethmoid plate was significantly reduced in the co-knocking group (282.50±61.77, t=5.29, P<0.001) compared with the control group (338.80±24.92). Transcriptome data and enrichment analysis showed that the differentially expressed genes were significantly enriched in the mitogen-activated protein kinase (MAPK) signaling pathway after the simultaneous knockdown of prickle1a and prickle1b in zebrafish. Conclusions: PRICKLE1 c.113C>T mutation might suppress the osteoblastic differentiation ability of jaw bone marrow mesenchymal stem cells by downregulating the MAPK signaling pathway, thereby involving the development of skeletal Class Ⅲ malocclusion.

Intranasal insulin protects against substantia nigra dopaminergic neuronal loss and alleviates motor deficits induced by 6-OHDA in rats

Protection of substantia nigra (SN) dopaminergic (DA) neurons by neurotrophic factors (NTFs) is one of the promising strategies in Parkinson's disease (PD) therapy. A major clinical challenge for NTF-based therapy is that NTFs need to be delivered into the brain via invasive means, which often shows limited delivery efficiency. The nose to brain pathway is a non-invasive brain drug delivery approach developed in recent years. Of particular interest is the finding that intranasal insulin improves cognitive functions in Alzheimer's patients. In vitro, insulin has been shown to protect neurons against various insults. Therefore, the current study was designed to test whether intranasal insulin could afford neuroprotection in the 6-hydroxydopamine (6-OHDA)-based rat PD model. 6-OHDA was injected into the right side of striatum to induce a progressive DA neuronal lesion in the ipsilateral SN pars compact (SNc). Recombinant human insulin was applied intranasally to rats starting from 24h post lesion, once per day, for 2 weeks. A battery of motor behavioral tests was conducted on day 8 and 15. The number of DA neurons in the SNc was estimated by stereological counting. Our results showed that 6-OHDA injection led to significant motor deficits and 53% of DA neuron loss in the ipsilateral side of injection. Treatment with insulin significantly ameliorated 6-OHDA-induced motor impairments, as shown by improved locomotor activity, tapered/ledged beam-walking performance, vibrissa-elicited forelimb-placing, initial steps, as well as methamphetamine-induced rotational behavior. Consistent with behavioral improvements, insulin treatment provided a potent protection of DA neurons in the SNc against 6-OHDA neurotoxicity, as shown by a 74.8% increase in tyrosine hydroxylase (TH)-positive neurons compared to the vehicle group. Intranasal insulin treatment did not affect body weight and blood glucose levels. In conclusion, our study showed that intranasal insulin provided strong neuroprotection in the 6-OHDA rat PD model, suggesting that insulin signaling may be a novel therapeutic target in broad neurodegenerative disorders.

Melatonin ameliorates brain injury induced by systemic lipopolysaccharide in neonatal rats

Our previous study showed that lipopolysaccharide (LPS)-induced brain injury in the neonatal rat is associated with nitrosative and oxidative stress. The present study was conducted to examine whether melatonin, an endogenous molecule with antioxidant properties, reduces systemic LPS-induced nitrosative and oxidative damage in the neonatal rat brain. Intraperitoneal (i.p.) injection of LPS (2mg/kg) was administered to Sprague-Dawley rat pups on postnatal day 5 (P5), and i.p. administration of melatonin (20mg/kg) or vehicle was performed 5min after LPS injection. Sensorimotor behavioral tests were performed 24h after LPS exposure, and brain injury was examined after these tests. The results show that systemic LPS exposure resulted in impaired sensorimotor behavioral performance, and acute brain injury, as indicated by the loss of oligodendrocyte immunoreactivity and a decrease in mitochondrial activity in the neonatal rat brain. Melatonin treatment significantly reduced LPS-induced neurobehavioral disturbances and brain damage in neonatal rats. The neuroprotective effect of melatonin was associated with attenuation of LPS-induced nitrosative and oxidative stress, as indicated by the decreased nitrotyrosine- and 4-hydroxynonenal-positive staining in the brain following melatonin and LPS exposure in neonatal rats. Further, melatonin significantly attenuated LPS-induced increases in the number of activated microglia in the neonatal rat brain. The protection provided by melatonin was also associated with a reduced number of inducible nitric oxide synthase (iNOS)+ cells, which were double-labeled with ED1 (microglia). Our results show that melatonin prevents the brain injury and neurobehavioral disturbances induced by systemic LPS exposure in neonatal rats, and its neuroprotective effects are associated with its impact on nitrosative and oxidative stress.

Celecoxib attenuates systemic lipopolysaccharide-induced brain inflammation and white matter injury in the neonatal rats

Lipopolysaccharide (LPS)-induced white matter injury in the neonatal rat brain is associated with inflammatory processes. Cyclooxygenase-2 (COX-2) can be induced by inflammatory stimuli, such as cytokines and pro-inflammatory molecules, suggesting that COX-2 may be considered as the target for anti-inflammation. The objective of the present study was to examine whether celecoxib, a selective COX-2 inhibitor, can reduce systemic LPS-induced brain inflammation and brain damage. Intraperitoneal (i.p.) injection of LPS (2mg/kg) was performed in postnatal day 5 (P5) of Sprague-Dawley rat pups and celecoxib (20mg/kg) or vehicle was administered i.p. 5 min after LPS injection. The body weight and wire-hanging maneuver test was performed 24h after the LPS exposure, and brain injury was examined after these tests. Systemic LPS exposure resulted in an impairment of behavioral performance and acute brain injury, as indicated by apoptotic death of oligodendrocytes (OLs) and loss of OL immunoreactivity in the neonatal rat brain. Treatments with celecoxib significantly reduced systemic LPS-induced neurobehavioral disturbance and brain damage. Celecoxib administration significantly attenuated systemic LPS-induced increments in the number of activated microglia and astrocytes, concentrations of IL-1β and TNFα, and protein levels of phosphorylated-p38 MAPK in the neonatal rat brain. The protection of celecoxib was also associated with a reduction of systemic LPS-induced COX-2+ cells which were double labeled with GFAP+ (astrocyte) cells. The overall results suggest that celecoxib was capable of attenuating the brain injury and neurobehavioral disturbance induced by systemic LPS exposure, and the protective effects are associated with its anti-inflammatory properties.

Neonatal lipopolysaccharide exposure induces long-lasting learning impairment, less anxiety-like response and hippocampal injury in adult rats

Infection during early neonatal period has been shown to cause lasting neurological disabilities and is associated with the subsequent impairment in development of learning and memory ability and anxiety-related behavior in adults. We have previously reported that neonatal lipopolysaccharide (LPS) exposure resulted in cognitive deficits in juvenile rats (P21); thus, the goal of the present study was to determine whether neonatal LPS exposure has long-lasting effects in adult rats. After an LPS (1mg/kg) intracerebral (i.c.) injection in postnatal day 5 (P5) Sprague-Dawley female rat pups, neurobehavioral tests were carried out on P21 and P22, P49 and P50 or P70 and P71 and brain injury was examined at 66days after LPS injection (P71). Our data indicate that neonatal LPS exposure resulted in learning deficits in the passive avoidance task, less anxiety-like (anxiolytic-like) responses in the elevated plus-maze task, reductions in the hippocampal volume and the number of neuron-specific nuclear protein (NeuN)+ cells, as well as axonal injury in the CA1 region of the middle dorsal hippocampus in P71 rats. Neonatal LPS exposure also resulted in sustained inflammatory responses in the P71 rat hippocampus, as indicated by an increased number of activated microglia and elevation of interleukin-1β content in the rat hippocampus. This study reveals that neonatal LPS exposure causes persistent injuries to the hippocampus and results in long-lasting learning disabilities, and these effects are related to the chronic inflammation in the rat hippocampus.

Intranasal administration of insulin-like growth factor-1 protects against lipopolysaccharide-induced injury in the developing rat brain

Our previous studies show that insulin-like growth factor-1 (IGF-1) can either protect against or increase lipopolysaccharide (LPS)-induced damage in the developing brain, depending on the dose, when it is co-administered with LPS through intracerebral injection. To further explore effects of IGF-1 on central inflammation associated brain injury, IGF-1 was administered through intranasal infusion in the current study. Postnatal day 5 (P5) rats were exposed to LPS at a dose of 1 μg/g body weight or sterile saline through intracerebral injection. Recombinant human insulin-like growth factor-1 (rhIGF-1) at a dose of 50 μg/pup or vehicle was administered intranasally 1 or 2 h after the LPS injection. Neonatal LPS exposure resulted in oligodendrocyte (OL) and white matter injury in the P6 or P21 rat brain. The damages include dilatation of lateral ventricles, pyknotic cell death, loss of OL progenitor cells and mature OLs in the cingulum area, and impairment of myelination at the corpus callosum area. Neurological dysfunctions were observed in juvenile rats with neonatal LPS exposure. Intranasal IGF-1 treatment at either 1 or 2 h after LPS exposure significantly attenuated LPS-induced brain injury and improved some behavioral deficits. Intranasal IGF-1 treatment also reduced infiltration of polymorphonuclear (PMN) leukocytes and activation of microglia in the rat brain 24 h after LPS exposure, but it did not prevent the elevation in concentrations of interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNFα) in the LPS-exposed rat brain during the first 24 h. This is an indication that direct anti-inflammation might not be the primary mechanism for the protection of IGF-1, and other mechanisms, such as anti-apoptotic effects, are likely involved in its protective effects.

Alpha-Phenyl-n-tert-butyl-nitrone attenuates lipopolysaccharide-induced neuronal injury in the neonatal rat brain

Although white matter damage is a fundamental neuropathological feature of periventricular leukomalacia (PVL), the motor and cognitive deficits observed later in infants with PVL indicate the possible involvement of cerebral neuronal dysfunction. Using a previously developed rat model of white matter injury induced by cerebral lipopolysaccharide (LPS) injection, we investigated whether LPS exposure also results in neuronal injury in the neonatal brain and whether alpha-phenyl-n-tert-butyl-nitrone (PBN), an antioxidant, offers protection against LPS-induced neuronal injury. A stereotactic intracerebral injection of LPS (1 mg/kg) was performed in Sprague-Dawley rats (postnatal day 5) and control rats were injected with sterile saline. LPS exposure resulted in axonal and neuronal injury in the cerebral cortex as indicated by elevated expression of beta-amyloid precursor protein, altered axonal length and width, and increased size of cortical neuronal nuclei. LPS exposure also caused loss of tyrosine hydroxylase positive neurons in the substantia nigra and the ventral tegmental areas of the rat brain. Treatments with PBN (100 mg/kg) significantly reduced LPS-induced neuronal and axonal damage. The protection of PBN was associated with an attenuation of oxidative stress induced by LPS as indicated by the reduced number of 4-hydroxynonenal, malondialdehyde or nitrotyrosine positive cells in the cortical area following LPS exposure, and with the reduction in microglial activation stimulated by LPS. The finding that an inflammatory environment may cause both white matter and neuronal injury in the neonatal brain supports the possible anatomical correlate for the intellectual deficits and the other cortical and deep gray neuronal dysfunctions associated with PVL. The protection of PBN may indicate the potential usefulness of antioxidants for treatment of these neuronal dysfunctions.

Role of interleukin-6 in lipopolysaccharide-induced brain injury and behavioral dysfunction in neonatal rats

There are increasing data in support of the hypothesis that inflammatory cytokines are involved in neonatal white matter damage. Despite extensive study of the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-1beta, the role of interleukin-6 in the development of white matter damage is largely unknown. In the present study, the role(s) of interleukin-6 in mediating lipopolysaccharide-induced brain injury and behavioral changes was investigated by the intracerebral injection of lipopolysaccharide with interleukin-6 neutralizing antibody in the 5-day-old rat brain. Brain injury was examined in brain sections at postnatal day 8 and postnatal day 21. Behavioral tests including righting reflex, wire hanging maneuver, cliff avoidance, locomotor activity, gait analysis, responses in the elevated plus-maze and passive avoidance were performed from postnatal day 3 to postnatal day 21. Changes in astroglia, microglia and oligodendrocytes were studied using immunohistochemistry in the postnatal day 21 rat brain. Our results show that interleukin-6 antibody attenuated lipopolysaccharide-induced brain lateral ventricle dilation and improved neurobehavioral performance. Interleukin-6 antibody also suppressed lipopolysaccharide-induced astrogliosis and microglial activation, and increased the number of oligodendrocytes in white matter. However, no changes of tumor necrosis factor-alpha and interleukin-1beta were detected. In contrast, no histopathological changes and glial activation were observed in rats injected with only interleukin-6. The present study indicates that the contribution to brain injury by interleukin-6 depends on its interaction with other lipopolysaccharide-induced agents and not on interleukin-6 alone.

Minocycline alleviates hypoxic-ischemic injury to developing oligodendrocytes in the neonatal rat brain

The role of minocycline in preventing white matter injury, in particular the injury to developing oligodendrocytes was examined in a neonatal rat model of hypoxia-ischemia. Hypoxia-ischemia was achieved through bilateral carotid artery occlusion followed by exposure to hypoxia (8% oxygen) for 15 min in postnatal day 4 Sprague-Dawley rats. A sham operation was performed in control rats. Minocycline (45 mg/kg) or normal phosphate-buffered saline was administered intraperitoneally 12 h before and immediately after bilateral carotid artery occlusion+hypoxia and then every 24 h for 3 days. Nissl staining revealed pyknotic cells in the white matter area of the rat brain 1 and 5 days after hypoxia-ischemia. Hypoxia-ischemia insult also resulted in apoptotic oligodendrocyte cell death, loss of O4+ and O1+ oligodendrocyte immunoreactivity, and hypomyelination as indicated by decreased myelin basic protein immunostaining and by loss of mature oligodendrocytes in the rat brain. Minocycline significantly attenuated hypoxia-ischemia-induced brain injury. The protective effect of minocycline was associated with suppression of hypoxia-ischemia-induced microglial activation as indicated by the decreased number of activated microglia, which were also interleukin-1beta and inducible nitric oxide synthase expressing cells. The protective effect of minocycline was also linked with reduction in hypoxia-ischemia-induced oxidative and nitrosative stress as indicated by 4-hydroxynonenal and nitrotyrosine positive oligodendrocytes, respectively. The reduction in hypoxia-ischemia-induced oxidative stress was also evidenced by the decreases in the content of 8-isoprostane in the minocycline-treated hypoxia-ischemia rat brain as compared with that in the vehicle-treated hypoxia-ischemia rat brain. The overall results suggest that reduction in microglial activation may protect developing oligodendrocytes in the neonatal brain from hypoxia-ischemia injury.

Minocycline attenuates lipopolysaccharide-induced white matter injury in the neonatal rat brain

Our previous studies have shown that intracerebral administration of endotoxin, lipopolysaccharide (LPS), induces selective white matter injury and hypomyelination in the neonatal rat brain and that the LPS-induced brain injury is associated with activation of microglia. To test the hypothesis that inhibition of microglial activation may protect against LPS-induced white matter injury, we examined roles of minocycline, a putative suppressor of microglial activation, on LPS-induced brain injury in the neonatal rat. A stereotactic intracerebral injection of LPS (1 mg/kg) was performed in postnatal day 5 Sprague-Dawley rats and control rats were injected with sterile saline. Minocycline (45 mg/kg) was administered intraperitoneally 12 h before and immediately after LPS injection and then every 24 h for 3 days. Inflammatory responses, activation of microglia and brain injury were examined 1 and 3 days after LPS injection. LPS injection resulted in brain injury in selective brain areas, including bilateral ventricular enlargement, cell death at the sub- and periventricular areas, loss of O4+ and O1+ oligodendrocyte (OL) immunoreactivity and hypomyelination, as indicated by decreased myelin basic protein immunostaining, in the neonatal rat brain. Minocycline administration significantly attenuated LPS-induced brain injury in these rat brains. The protective effect of minocycline was associated with suppressed microglial activation as indicated by the decreased number of activated microglial cells following LPS stimulation and with consequently decreased elevation of interleukin 1beta and tumor necrosis factor-alpha concentrations induced by LPS and a reduced number of inducible nitric oxide synthase expressing cells. Protection of minocycline was also linked with the reduction in LPS-induced oxidative stress, as indicated by 4-hydroxynonenal positive OLs. The overall results suggest that reduction in microglial activation may protect the neonatal brain from LPS-induced white matter injury and inhibition of microglial activation might be an effective approach for the therapeutic treatment of infection-induced white matter injury.

Changes in the brain kappa-opioid receptor levels of rats in withdrawal from physical dependence upon butorphanol

Changes in kappa-opioid receptor levels have been implicated in the development of physical dependence upon and withdrawal from the mixed agonist-antagonist opioid, butorphanol. Immunoblotting analysis was performed to determine the levels of kappa- and mu-opioid receptors in brain regions of rats in withdrawal from dependence upon butorphanol or morphine. Physical dependence was induced by a 72 h i.c.v. infusion with either butorphanol or morphine (26 nmol/microl/h). Withdrawal was subsequently precipitated by i.c.v. challenge with naloxone (48 nmol/5 microl/rat), administered 2 h following cessation of butorphanol or morphine infusion. Immunoblotting analysis of kappa-opioid receptors from butorphanol-withdrawal rats showed significant increases in 11 of 21 brain regions examined, including the nucleus accumbens, amygdala, dorsomedial hypothalamus, hypothalamus, paraventricular thalamus, thalamus, presubiculum, and locus coeruleus, when compared with saline treated, non-dependent controls. In addition, significant reductions were found in the hippocampus and in cortical brain regions, including the parietal cortex and temporal cortex from butorphanol-withdrawal rats. These findings contrasted with those from morphine-withdrawal rats, in which the only changes noted were increases in the thalamus and paraventricular thalamus. Changes in the levels of the mu-opioid receptor protein were observed in 11 of 21 brain regions examined in morphine-withdrawal rats, but only in three of 21 in butorphanol-withdrawal rats. These results implicate a substantive and largely unique role for kappa-opioid receptors in mediation of the development of physical dependence upon, and the expression of withdrawal from, butorphanol, as opposed to the prototypical opioid analgesic, morphine.

Region specific increase of dopamine receptor D1/D2 mRNA expression in the brain of mu-opioid receptor knockout mice

Previous pharmacological studies have indicated the possible existence of functional interactions between opioidergic and dopaminergic neurons in the CNS. In this study, the expression of mRNAs encoding dopamine receptor D1/D2 was examined to investigate whether there is a change in the dopamine pathway of mice lacking the mu-opioid receptor by in situ hybridization technique. In the mu-opioid receptor knockout mice, the expression of dopamine receptor D1 mRNA was increased in the olfactory tubercle, nucleus accumbens, caudate putamen, and the layer VI of the neocortex compared with that of wild-type mice. The expression of dopamine receptor D2 mRNA was also increased in the olfactory tubercle, caudate putamen, and the nucleus accumbens of mu-opioid receptor knockout mice. These results indicate that there are compensational changes in the dopaminergic systems of mu-opioid receptor knockout mice.

Forskolin inhibits 5-hydroxytryptamine-induced phosphoinositide hydrolysis and Ca+2 Mobilisation in canine cultured aorta smooth muscle cells

The effect of forskolin on 5-hydroxytryptamine (5-HT)-induced inositol phosphate (IP) and Ca2+ mobilisation was investigated in canine cultured aorta smooth muscle cells (ASMCs). Pretreatment of ASMCs with forskolin attenuated 5-HT-induced IP accumulation and Ca2+ mobilisation in a time- and concentration-dependent manner. The half-maximal effects (pEC50) of forskolin to attenuate IP and Ca2+ responses to 5-HT occurred at concentrations of 6.28 and 6.64, respectively. Pretreatment of ASMCs with cholera toxin caused a similar inhibition on 5-HT-induced responses. Even after treatment with forskolin for 24 h, the 5-HT-induced responses were still inhibited. The inhibitory effect of forskolin resulted from both a depression of the maximal response and a shift to the right of the concentration-effect curves of 5-HT in these responses. The water-soluble forskolin analogue L-858051 [7-deacetyl-7beta-(gamma-N-methylpiperazino)-butyryl forskolin] significantly inhibited the 5-HT-stimulated IP accumulation. In contrast, the addition of 1,9-dideoxy forskolin, an inactive forskolin analogue, had little effect on IP response. Moreover, SQ-22536 [9-(tetrahydro-2-furanyl)-9-H-purin-6-amine], an inhibitor of adenylate cyclase, and both H-89 [N-(2-aminoethyl)-5-iosquinolinesulphonamide] and HA-1004 [N-(2-guanidinoethyl)-5-iosquinolinesulphonamide], inhibitors of cAMP-dependent protein kinase (PKA), attenuated the ability of forskolin to inhibit the 5-HT-stimulated accumulation of IP in ASMCs. These results indicate that activation of cAMP/PKA might inhibit the 5-HT-stimulated IP accumulation and consequently reduce Ca2+ mobilisation, or inhibit both responses independently.

Regulation of 5-hydroxytryptamine-induced signal transduction in canine cultured aorta smooth muscle cells by phorbol ester

Regulation of the increase in inositol phosphates (IPs) production and intracellular Ca2+ concentration ([Ca2+]i) by protein kinase C (PKC) was investigated in cultured canine aorta smooth muscle cells (ASMCs). Stimulation of ASMCs by 5-hydroxytryptamine (5-HT) led to IPs formation and caused an initial transient [Ca2+]i peak followed by a sustained elevation of [Ca2+]i in a concentration-dependent manner. Pretreatment of ASMCs with phorbol 12-myristate 13-acetate (PMA) for 30 min almost abolished the 5-HT-induced IPs formation and Ca2+ mobilization. This inhibition was reduced after long-term incubating the cells with PMA. Prior treatment of ASMCs with staurosporine or GF109203X, PKC inhibitors, inhibited the ability of PMA to attenuate 5-HT-induced responses, suggesting that the inhibitory effect of PMA is mediated through the activation of PKC. In parallel with the effect of PMA on the 5-HT-induced IP formation and Ca2+ mobilization, the translocation and down-regulation of PKC isozymes were determined by Western blotting with antibodies against different PKC isozymes. The results revealed that treatment of ASMCs with PMA for various times, translocation of PKC-alpha, betaI, betaII, delta, epsilon, theta, and zeta isozymes from the cytosol to the membrane was seen after 5-min, 30-min, 2-h, and 4-h treatment. However, 24-h treatment caused a partial down-regulation of these PKC isozymes. In conclusion, these results demonstrate that translocation of PKC-alpha, betaI, betaII, delta, epsilon, theta, and zeta induced by PMA caused an attenuation of 5-HT-induced IPs accumulation and Ca2+ mobilization in ASMCs.

5-Hydroxytryptamine-induced phosphoinositide hydrolysis and Ca2+ mobilisation in canine cultured aorta smooth muscle cells

The effect of 5-hydroxytryptamine (5-HT) on phospholipase C (PLC)-mediated phosphoinositide (PI) hydrolysis and intracellular Ca2+ ([Ca2+]i) changes was investigated in canine cultured aorta smooth muscle cells (ASMCs). 5-HT-stimulated inositol phosphate (IP) accumulation was time and concentration dependent with a half-maximal response (pEC50) and a maximal response at 6.4 and 10 microM, n = 6, respectively. Stimulation of ASMCs by 5-HT produced an initial transient peak followed by a sustained, concentration-dependent elevation in [Ca+]i. The half-maximal response (pEC50) values of 5-HT for the peak and sustained plateau were 7.1 and 6.9, respectively. Ketanserin and mianserin (1 and 3 nM), 5-HT2A antagonists, were equipotent and had high affinity in antagonising the 5-HT-induced IP accumulation and [Ca2+]i change with pK(B) values of 8.6-9.1 and 8.6-9.4, respectively. In contrast, the concentration-effect curves of 5-HT-induced IP and [Ca2+]i responses were not shifted until the concentrations of NAN-190 and metoctopramide (5-HT1A and 5-HT3 receptor antagonists, respectively) were increased to as high as 1 microM with pK(B) values of 5.7-6.3 and 6.1-6.6, respectively, indicating that the 5-HT receptor-mediated responses had low affinity for these antagonists. Pre-treatment of ASMCs with pertussis toxin (100 ng/mL, 24 h) caused a significant inhibition of 5-HT-induced IP accumulation and [Ca2+]i change in ASMCs. Depletion of external Ca2+ or removal of Ca2+ by addition of EGTA led to a significant attenuation of IP accumulation and [Ca2+]i change induced by 5-HT. Influx of external Ca2+ was required for the 5-HT-induced responses, because Ca2+-channel blockers--verapamil, nifedipine and Ni2+--partly inhibited the 5-HT-induced IP accumulation and Ca2+ mobilisation. The sustained elevation of [Ca2+]i response to 5-HT was dependent on the presence of external Ca2+. Removal of external Ca2+ by addition of 5 mM EGTA during the sustained phase caused a rapid decline in [Ca2+]i to lower than the resting level. The sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+ in the continued presence of 5-HT. These results demonstrate that 5-HT directly stimulates PLC-mediated PI hydrolysis and Ca2+ mobilisation, at least in part, through a pertussis toxin-sensitive G protein in canine ASMCs. 5-HT2A receptors may be predominantly mediating IP accumulation, and subsequently IP-induced Ca2+ mobilisation may function as the transducing mechanism for 5-HT-stimulated contraction of aorta smooth muscle.

Effect of forskolin on bradykinin-induced calcium mobilization in cultured canine tracheal smooth muscle cells

The effects of increases in intracellular adenosine 3':5'-cyclic monophosphate (cyclic AMP) on bradykinin (BK)-induced generation of inositol phosphates (IPs) and Ca2+ mobilization were investigated in canine cultured tracheal smooth muscle cells (TSMCs). Pretreatment of TSMCs with either forskolin or dibutyryl cyclic AMP attenuated BK-stimulated responses. The inhibitory effects of these agents produced both a depression of the maximal response and a shift to the right of the concentration-response curves of BK. The water-soluble forskolin analogue L-858051, 7-deacetyl-7 beta-(r-N-methylpiperazino)-butyryl forskolin, significantly attenuated BK-stimulated IPs accumulation, while 1,9-dideoxy forskolin, an inactive forskolin, had little effect on IPs response. Moreover, SQ-22536, 9-(tetrahydro-2-furanyl)-9-H-purin-6-amine, an inhibitor of adenylate cyclase, and both H-89, N-(2-aminoethyl)-5-isoquinolinesulfonamide, and HA-1004, N-(2-guanidinoethyl)-5-isoquinolinesulfonamide, inhibitors of cyclic AMP-dependent protein kinase (PKA), reversed the ability of forskolin to attenuate BK-stimulated IPs accumulation. The KD and Bmax, values of the BK receptor for [3H]BK binding were not significantly changed by forskolin treatment for 30 min and 4 h. The AlF4(-)-induced IPs accumulation was attenuated by forskolin, indicating that G protein(s) are directly activated by AlF4- and uncoupled to phospholipase C by forskolin treatment. These results suggest that activation of cyclic AMP/PKA might inhibit the BK-stimulated PI breakdown and consequently reduce the [Ca2+]i increases or inhibit independently both responses, which is distal to the BK receptor in canine cultured TSMCs.

Regulation of 5-hydroxytryptamine-induced calcium mobilization by cAMP-elevating agents in cultured canine tracheal smooth muscle cells

The effects of increases in cellular adenosine 3'5'-cyclic monophosphate (cAMP) on 5-hydroxytryptamine-(5-HT-) induced generation of inositol phosphates (IPs) and increases in intracellular Ca2+ ([Ca2+]i) were investigated using canine cultured tracheal smooth muscle cells (TSMCs). Cholera toxin and forskolin induced concentration- and time-dependent cAMP formation with half-maximal effects (-logEC50) produced at concentrations of 7.0 +/- 0.5 and 4.9 +/- 0.4 respectively. Pretreatment of TSMCs with either forskolin or dibutyryl cAMP inhibited 5-HT-stimulated responses. Even after treatment for 24h, these agents still inhibited the 5-HT-induced Ca2+ mobilization. The inhibitory effects of these agents produced both depression of the maximal response and a shift to the right of the concentration response curves of 5-HT. The water-soluble forskolin analogue L-858051 [7-deacetyl-7beta-(gamma-N-methylpiperazino)-butyryl forskolin] significantly inhibited the 5-HT-stimulated accumulation of IPs. In contrast, the addition of 1,9-dideoxy forskolin, an inactive forskolin analogue, had little effect on this response. Moreover, SQ-22536 [9-(tetrahydro-2-furanyl)-9-H-purin-6-amine], an inhibitor of adenylate cyclase, and both H-89 [N-(2-aminoethyl)-5-isoquinolinesulphonamide] and HA-1004[N-(2-guanidinoethyl)-5-isoquinolinesulphonamide], inhibitors of cAMP-dependent protein kinase (PKA), attenuated the ability of forskolin to inhibit the 5-HT-stimulated accumulation of IPs. These results suggest that activation of cAMP/PKA was involved in these inhibitory effects of forskolin. The AlF4--induced accumulation of IPs was inhibited by forskolin, suggesting that G protein(s) are directly activated by AlF4-- and uncoupled from phospholipase C by forskolin treatment. These results suggest that activation of cAMP/PKA might inhibit the 5-HT-stimulated phosphoinositide breakdown and consequently reduce the [Ca2+]i increase or inhibit both responses independently.

Effect of cAMP elevating agents on carbachol-induced phosphoinositide hydrolysis and calcium mobilization in cultured canine tracheal smooth muscle cells

The effects of increases in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) on carbachol-induced generation of inositol phosphates (IPs) and increases in intracellular Ca2+ ([Ca2+]i) were investigated in canine cultured tracheal smooth muscle cells (TSMCs). The cAMP elevating agents, cholera toxin (CTX) and forskolin, induced concentration- and time-dependent cAMP formation with half-maximal effects (-logEC50) at concentrations of 7.6 +/- 1.3 g/ml and 4.8 +/- 0.9 M, respectively. Forskolin caused a concentration-dependent inhibition of carbachol-induced increase in [Ca2+]i with half-maximal inhibition (-logEC50) at 5.2 +/- 0.7 M. Pretreatment of TSMCs with either CTX (10 micrograms/ml, 4 h), forskolin (10-100 microM, 30 min), or dibutyryl cAMP (1 mM, 30 min) inhibited carbachol-stimulated Ca2+ mobilization and IPs accumulation. The inhibitory effects of these agents produced both depression of the maximal response and a shift to the right of the concentration-response curve of carbachol without changing the EC50 values. After treatment with forskolin for 24 h, carbachol-induced IPs accumulation and Ca2+ mobilization were close to those of control group. SQ-22536 [9-(tetrahydro-2-furanyl)-9H-purin-6-amine, 10 microM], an inhibitor of adenylate cyclase, and HA-1004 [N-(2-guanidinoethyl)-5-isoquinolinesulfonamide hydrochloride, 50 microM], an inhibitor of cAMP-dependent protein kinase (PKA), attenuated the ability of forskolin to inhibit carbachol-induced IPs accumulation. Moreover, the inactive analogue of forskolin, 1,9-dideoxy forskolin, did not inhibit these responses evoked by carbachol, suggesting that activation of cAMP/PKA was involved in these inhibitory effects of forskolin. The KD and Bmax values of the muscarinic receptor (mAChR) for [3H]-N-methyl scopolamine binding were not significantly changed by forskolin treatment for 30 min and 24 h, suggesting that the inhibitory effect of forskolin is distal to the mAChR. The locus of this inhibition was further investigated by examining the effect of forskolin treatment on AIF4(-)-stimulated IPs accumulation in canine TSMCs. The AIF4(-)-induced response was inhibited by forskolin, supporting the notion that G protein(s) are directly activated by AIF4- and uncoupled to phospholipase C by forskolin treatment. We conclude that cAMP elevating agents inhibit carbachol-stimulated generation of IPs and Ca2+ mobilization in canine cultured TSMCs. Since generation of IPs and increases in [Ca2+]i are very early events in the activation of mAChRs, attenuation of these events by cAMP elevating agents might well contribute to the inhibitory effect of cAMP on tracheal smooth muscle formation.