Ca2+ fluxes and protein phosphorylation in stimulus-secretion coupling of basophils

Carbonyl cyanide 3-chlorophenylhydrazone induced the imbalance of mitochondrial homeostasis in the liver of Megalobrama amblycephala: A dynamic study

Carbonylcyanide-3-chlorophenylhydrazone (CCCP) is a protonophore, which causes uncoupling of proton gradient in the inner mitochondrial membrane, thus inhibiting the rate of ATP synthesis. However, this information is manly derived from mammals, while its effects on the mitochondrial homeostasis of aquatic animals are largely unknown. In this study, the mitochondrial homeostasis of a carp fish Megalobrama amblycephala was investigated systematically in a time-course manner by using CCCP. Fish was injected intraperitoneally with CCCP (1.8 mg/kg per body weight) and DMSO (control), respectively. The results showed that CCCP treatment induced hepatic mitochondrial oxidative stress, as was evidenced by the significantly increased MDA and PC contents coupled with the decreased SOD and MnSOD activities. Meanwhile, mitochondrial fission was up-regulated remarkably characterized by the increased transcriptions of Drp-1, Fis-1 and Mff. However, the opposite was true for mitochondrial fusion, as was indicative of the decreased transcriptions of Mfn-1, Mfn-2 and Opa-1. This consequently triggered mitophagy, as was supported by the accumulated mitochondrial autophagosomes and the increased protein levels of PINK1, Parkin, LC3-II and P62 accompanied by the increased LC3-II/LC3-I ratio. Mitochondrial biogenesis and function both decreased significantly addressed by the decreased activities of CS, SDH and complex I, IV and V, as well as the protein levels of PGC-1β coupled with the decreased transcriptions of TFAM, COX-1, COX-2 and ATP-6. Unlikely, DMSO treatment exerted little influence. Overall, CCCP treatment resulted in the imbalance of mitochondrial homeostasis in Megalobrama amblycephala by promoting mitochondrial oxidative stress, fission and mitophagy, but depressing mitochondrial fusion, biogenesis and function.

Effects of flavonoids on immune and inflammatory cell functions

No doubt can remain that the flavonoids have profound effects on the function of immune and inflammatory cells as determined by a large number and variety of in vitro and some in vivo observations. That these ubiquitous dietary chemicals may have significant in vivo effects on homeostasis within the immune system and on the behavior of secondary cell systems comprising the inflammatory response seems highly likely but more work is required to strengthen this hypothesis. Ample evidence indicates that selected flavonoids, depending on structure, can affect (usually inhibit) secretory processes, mitogenesis, and cell-cell interactions including possible effects on adhesion molecule expression and function. The possible action of flavonoids on the function of cytoskeletal elements is suggested by their effects on secretory processes. Moreover, evidence indicates that certain flavonoids may affect gene expression and the elaboration and effects of cytokines and cytokine receptors. How all of these effects are mediated is not yet clear but one important mechanism may be the capacity of flavonoids to stimulate or inhibit protein phosphorylation and thereby regulate cell function. Perhaps the counterbalancing effect of cellular protein tyrosine phosphatases will also be found to be affected by flavonoids. Some flavonoid effects can certainly be attributed to their recognized antioxidant and radical scavenging properties. A potential mechanism of action that requires scrutiny, particularly in relation to enzyme inhibition, is the redox activity of appropriately configured flavonoids. Finally, in a number of cell systems it seems that resting cells are not affected significantly by flavonoids but once a cell becomes activated by a physiological stimulus a flavonoid-sensitive substance is generated and interaction of flavonoids with that substance dramatically alters the outcome of the activation process.

The actions of inhibitors of diacylglycerol kinase and diacylglycerol lipase on histamine release from rat peritoneal mast cells

1. RHC 80267 and R59 022 are selective inhibitors of diacylglycerol (DAG) lipase and DAG kinase enzymes respectively. These inhibitors were examined with regard to their effects on oleoylacetylglycerol (OAG)-and anti-IgE- induced histamine secretion in rat peritoneal mast cells. 2. RHC 80267, 10 microM and R59 022, 50 microM both enhanced OAG-induced histamine release by 30% and 40% respectively. 3. In the concentration range 3-30 microM, R59 022 enhanced anti-IgE-induced histamine release by up to about 40%, whereas RHC 80267 was without effect. 4. The enhancement of anti-IgE-induced histamine release by R59 022 is consistent with a role for protein kinase C in transducing immunological signals to rat peritoneal mast cells. 5. The lack of effect of RHC 80267 in this situation may indicate that in the mast cell, DAG kinase is more active than DAG lipase in degrading physiological levels of DAG.

Membrane sialic acid influences basophil histamine release by interfering with calcium dependence

The influence of the cell membrane content of sialic acid on basophil histamine release was examined in vitro in allergic patients and normal controls. Enzymatical removal of sialic acid enhanced histamine release induced by allergen and anti-IgE, whereas an increase in membrane sialic acid content by insertion of sialic acid containing gangliosides into the membrane inhibited the mediator release. The reduction in membrane sialic acid content abolished the inhibitory capacity of the calcium channel antagonist nimodipine, whereas the inhibition produced by verapamil and lanthanum was not affected. This difference, together with the previous finding that alterations in membrane sialic acid content is reflected in the cell sensitivity to extracellular calcium, suggest an interaction between membrane sialic acid and the calcium channels involved in basophil histamine release.

Possible involvement of phosphorylation of a 36,000-dalton protein of rat basophilic leukemia (RBL-2H3) cell membranes in serotonin release

Phosphorylation of a 36,000-dalton (36k-Da) protein of rat basophilic leukemia (RBL-2H3) cell membranes was investigated. This phosphoprotein has been suggested to be the beta-subunit protein of the immunogloblin E (IgE) receptor of RBL-2H3 cells [Teshima et al., Biochem. biophys. Res. Commun. 125, 867-874 (1984)]. Phospholipids such as phosphatidyl serine, phosphatidyl inositol and phosphatidyl ethanolamine, which are known to be activators of protein kinase C, enhanced the phosphorylation of the 36K-Da protein. In contrast, 1-(5-isoquinoline sulfonyl)-2-methylpiperazine (H-7) which has been identified as a potent inhibitor of protein kinase C in vitro decreased incorporation of radioactive phosphate from [gamma-32P]ATP into this protein. These results indicate that the phosphorylation of the 36K-Da protein of RBL-2H3 cell membranes is catalyzed by protein kinase C. H-7 also inhibited the release of serotonin from RBL-2H3 cells stimulated with an antigen or calcium ionophore A23187 and 12-O-tetradecanoyl phorbol 13-acetate (TPA). Treatment of the antigen-stimulated cells with TPA caused a synergistic effect on the serotonin release. A similar effect was obtained by treatment of A23187-stimulated cells with TPA or 1-oleoyl-2-acetyl glycerol.

Histamine release induced by histone and phorbol ester from rat peritoneal mast cells

Histone 10 to 50 micrograms/ml released histamine from rat peritoneal mast cells in the absence of extracellular calcium. Extracellular calcium, 1 mM produced a slight shift of the histone dose-response curve to the right. In the absence of extracellular calcium, the histamine release-response to combined stimulation with histone and substance P was saturable. Neither histone nor substance P elicited any further response when one of these agonists alone was already eliciting a maximum response, although the cells were capable of a greater degree of histamine release in the presence of compound 48/80. In the presence of extracellular calcium, substance P at a concentration not by itself producing a response, acted synergistically with histone to induce histamine release. The substance P antagonist, SP-A, inhibited histamine release by histone. The phorbol ester, TPA, released histamine in a dose-dependent manner and this response was inhibited by SP-A. It is suggested that substance P and histone interact with a common site to release histamine and the role of protein kinase C in this release mechanism is discussed.