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Influences of cholecystokinin octapeptide on phosphoinositide turnover in neonatal-rat brain cells.

ABSTRACT: Cholecystokinin octapeptide (CCK-8) has been shown to be coupled to phosphoinositide turnover in pancreatic acini as well as in a kind of neuroblastoma cell and a human embryonic cell line. Little is known, however, about its link with phosphatidylinositol breakdown in the brain. The brains (minus cerebella) from 1-2-day-old neonatal rats were enzymically dissociated into single cells. The intact cells were prelabelled by incubation with myo-[3H]inositol for 3 h, and were then stimulated with agonists in the presence of 10 mM-LiCl. Carbachol at 1 mM induced an increase in InsP3 labelling in brain cells (peak at 30 min, and then a gradual decrease), and a static accumulation of InsP with time, whereas the labelling of InsP2 remained essentially unchanged. A very similar time-response curve was obtained for 10 nM-CCK-8 in stimulating phosphoinositide turnover. The dose-response curve for incubated brain cells revealed that the formation of InsP3 increased when the concentration of CCK-8 was increased from 0.1 to 10 nM. A further increase in CCK-8 concentration to 100-1000 nM resulted in a gradual decrease in InsP3 formation. InsP and InsP2 levels stayed relatively stable. The production of InsP3 stimulated by 10 nM-CCK-8 was dose-dependently suppressed by the CCK-A antagonist Devazepide in the concentration range 1-10 nM; the effect declined when the concentration was further increased to 100-1000 nM. In contrast, the CCK-B antagonist L365,260 showed a sustained suppression of InsP3 production at concentrations above 0.1 nM, i.e. in the range 1-1000 nM. The results provide evidence that CCK-8 stimulates the turnover of phosphoinositide and increases InsP3 labelling in dissociated neonatal-rat brain cells, in which both CCK-A and CCK-B receptors seem to be involved.

SUBMITTER: Zhang LJ

PROVIDER: S-EPMC1132873 | biostudies-other | 1992 Aug

REPOSITORIES: biostudies-other

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Project description:We have explored the hypothesis that the apparent greater efficiency of cholecystokinin (CCK-8) receptor-second messenger coupling compared with that of muscarinic receptor in Flow 9000 cells is due to differential feedback inhibitory control mechanisms. Pretreatment of Flow 9000 cells with the tumour-promoting protein kinase C (PKC)-activating agent 12-O-tetradecanoylphorbol 13-acetate (TPA) produced a time- and dose-dependent inhibition of CCK-8 and acetylcholine (ACh) stimulation of inositol phosphate production. The inhibition by TPA of ACh-induced PI (phosphoinositide) response involved reduction of the maximal response, but no change in the concentration of ACh required to evoke a half-maximal response. In contrast, TPA inhibition of CCK-8 responses could be overcome by increasing the CCK-8 concentrations. Flow 9000 cells pretreated with TPA exhibited a 52-68% reduction in [3H]quinuclidinyl benzilate ([3H]QNB) binding capacity, whereas [125I]CCK-8 binding was unchanged. In saponin-permeabilized Flow 9000 cells, TPA pretreatment had no effect on guanosine 5'-[gamma-thio]triphosphate (GTP[S])-induced inositol phosphate formation, indicating that G-protein linkage to phosphoinositidase C (PIC) was not affected. However, TPA significantly inhibited the potentiating effect of GTP[S] on CCK-8 and ACh activation of PI response, suggesting that the coupling between the receptors and the G-protein was impaired. The PKC-activator 1-oleoyl-2-acetylglycerol (OAG), a diacylglycerol analogue, also significantly reduced CCK-8 and ACh stimulation of inositol phosphate accumulation in these cells. Our results are consistent with the hypothesis that muscarinic activation of PI hydrolysis is subjected to rapid feedback inhibition via the 1,2-diacylglycerol-PKC pathway. CCK-receptor activation of PI turnover is modulated to a lesser extent, and this may partially explain apparent differences in the efficiency of receptor-second messenger coupling. It is proposed that TPA acting through PKC exerts its inhibitory action on muscarinic-agonist-mediated PI response mainly at the receptor level, whereas the inhibitory effect on CCK-8 response is at a site close to the receptor-G-protein coupling step.

Project description:Neonatal brain injury may impact brain development and lead to lifelong functional impairments. Hypoxic-ischemic encephalopathy (HIE) and congenital heart disease (CHD) are two common causes of neonatal brain injury differing in timing and mechanism. Maturation of whole-brain neural networks can be quantified during development using diffusion magnetic resonance imaging (dMRI) in combination with graph theory metrics. DMRI of 35 subjects with CHD and 62 subjects with HIE were compared to understand differences in the effects of HIE and CHD on the development of network topological parameters and functional outcomes. CHD newborns had worse 12-18 month language (P<0.01) and 30 month cognitive (P<0.01), language (P = 0.05), motor outcomes (P = 0.01). Global efficiency, a metric of brain integration, was lower in CHD (P = 0.03) than in HIE, but transitivity, modularity and small-worldness were similar. After controlling for clinical factors known to affect neurodevelopmental outcomes, we observed that global efficiency was highly associated with 30 month motor outcomes (P = 0.02) in both groups. To explore neural correlates of adverse language outcomes in CHD, we used hypothesis-based and data-driven approaches to identify pathways with altered structural connectivity. We found that connectivity strength in the superior longitudinal fasciculus (SLF) tract 2 was inversely associated with expressive language. After false discovery rate correction, a whole connectome edge analysis identified 18 pathways that were hypoconnected in the CHD cohort as compared to HIE. In sum, our study shows that neonatal structural connectivity predicts early motor development after HIE or in subjects with CHD, and regional SLF connectivity is associated with language outcomes. Further research is needed to determine if and how brain networks change over time and whether those changes represent recovery or ongoing dysfunction. This knowledge will directly inform strategies to optimize neurologic functional outcomes after neonatal brain injury.

Project description:Introduction: To limit extrauterine growth restriction, recent guidelines on nutrition of preterm neonates recommended high protein intake since the first day of life (DOL). The impact of this nutritional strategy on the brain is still controversial. We aimed to evaluate the effects of protein intake on early cerebral growth in very low birth weight newborns. Materials and Methods: We performed serial cranial ultrasound (cUS) scans at 3-7 DOL and at 28 DOL in very low birth weight newborns consecutively observed in the neonatal intensive care unit. We analyzed the relation between protein intake and cerebral measurements at 28 DOL performed by cUS. Results: We enrolled 100 newborns (gestational age 29 ± 2 weeks, birth weight 1,274 ± 363 g). A significant (p < 0.05) positive correlation between enteral protein intake and biparietal diameter (r = 0.490**), occipital-frontal diameter (r = 0.608**), corpus callosum (length r = 0.293*, genu r = 0.301*), caudate head (right r = 0.528**, left r = 0.364**), and cerebellum (transverse diameter r = 0.440**, vermis height r = 0.356**, vermis width r = 0.377**) was observed at 28 DOL. Conversely, we found a significant negative correlation of protein intake given by parenteral nutrition (PN) with biparietal diameter (r = -0.524**), occipital-frontal diameter (r = -0.568**), body of corpus callosum (r = -0.276*), caudate head (right r = -0.613**, left r = -0.444**), and cerebellum (transverse diameter r = -0.403**, vermis height r = -0.274*, vermis width r = -0.462**) at 28 DOL. Multivariate regression analysis showed that measurements of occipital-frontal diameter, caudate head, and cerebellar vermis at 28 DOL depend positively on protein enteral intake (r = 0.402*, r = 0.305*, and r = 0.271*) and negatively by protein parenteral intake (r = -0.278*, r = -0.488*, and r = -0.342*). Conclusion: Brain development in neonatal life depends on early protein intake. High protein intake affects cerebral structures' measurements of preterm newborn when administered by PN. Positive impact on brain development encourages the administration of recommended protein intake mainly by enteral nutrition.

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Influences of cholecystokinin octapeptide on phosphoinositide turnover in neonatal-rat brain cells.

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