Fibroblast growth factors mobilize peritoneal macrophage intracellular calcium

FGF/FGFR signaling in health and disease

Growing evidences suggest that the fibroblast growth factor/FGF receptor (FGF/FGFR) signaling has crucial roles in a multitude of processes during embryonic development and adult homeostasis by regulating cellular lineage commitment, differentiation, proliferation, and apoptosis of various types of cells. In this review, we provide a comprehensive overview of the current understanding of FGF signaling and its roles in organ development, injury repair, and the pathophysiology of spectrum of diseases, which is a consequence of FGF signaling dysregulation, including cancers and chronic kidney disease (CKD). In this context, the agonists and antagonists for FGF-FGFRs might have therapeutic benefits in multiple systems.

Calcium channel antagonist effect on in vitro meningioma signal transduction pathways after growth factor stimulation

OBJECTIVE

We have previously demonstrated that calcium channel antagonists inhibit the growth of human meningiomas in culture after stimulation with growth factors. This study examined the effects of these drugs on signaling transduction pathways in an attempt to elucidate potential mechanisms by which this growth inhibition is mediated.

METHODS

Primary cell cultures from patients with intracranial meningiomas were established. Cell growth studies were performed with inhibitors and stimulators of tyrosine kinase signal transduction. Intracellular calcium changes and inositol phosphate production were measured after growth factor exposure, with or without pretreatment by calcium channel antagonists.

RESULTS

The growth of meningiomas in culture can be inhibited by tyrosine kinase receptor inhibitors. Inhibitors and stimulators of phospholipase C can stimulate or inhibit the growth of in vitro meningiomas, respectively. Calcium channel antagonists inhibit intracellular calcium changes induced by serum and epidermal growth factor. Inositol phosphate production is increased after growth factor stimulation, and calcium channel antagonists potentiate this effect.

CONCLUSION

Calcium channel antagonists interfere with intracellular signaling pathways of cultured meningioma cells. This inhibition is unrelated to voltage-sensitive calcium channels. The findings of this project may aid in the understanding of the signal transduction mechanisms involved in growth factor-mediated meningioma proliferation and may lead to clinically relevant strategies for growth inhibition.

Effect of acidic fibroblast growth factor (aFGF) on phagocytosis in mouse peritoneal macrophages

The effects of acidic fibroblast growth factor (aFGF) on phagocytosis in peritoneal macrophages from thioglycollate-elicited mice were examined using flow cytometry. aFGF enhanced phagocytosis of fluorescein isothiocyanate-labeled latex particles in a dose-dependent manner. Basic fibroblast growth factor (bFGF) also enhanced phagocytosis. This study suggests that aFGF can modulate an important activity of macrophages.

Enhancement of phagocytosis in mouse peritoneal macrophages by fragments of acidic fibroblast growth factor (aFGF)

To characterize the effects of acidic fibroblast growth factor (aFGF) in mouse peritoneal macrophages, the effects of aFGF fragments on phagocytosis were examined. Fragments that were tested included aFGF(1-15), aFGF(1-20), aFGF(1-29), Ala16-aFGF(1-29), aFGF(9-29) and aFGF(114-140). aFGF(1-29) induced an enhancement of phagocytosis in a dose-dependent manner and was more effective than any other fragments tested. Even in Ca2+-and Mg2+-free solutions, phagocytosis was enhanced by aFGF(1-29). However, the enhancement induced by aFGF(1-29) was completely inhibited in the presence of mannan (4 mg/ml). Furthermore, the enhancement of phagocytosis by aFGF(1-29) was suppressed by heparin (100 microg/ml). The results of the present study suggest that the active region of aFGF that is responsible for the enhancement of phagocytosis corresponds to residues 15-29 and that phagocytosis, which is modulated by aFGF, is independent of extracellular Ca2+ and is mediated by mannose receptors.

A chelate theory for the mechanism of action of aspirin-like drugs

Two hundred years after the discovery of the pharmaceutical usefulness of aspirin, it and aspirin-like drugs, a family with an ever-increasing number of members, are an indispensable part of modern life. However, the question as to how these drugs work in the body has remained unsettled. It is postulated here that this group of drugs may exert their therapeutic (and adverse) effects by chelating various physiologically important metallic cations in the body. The chelate theory is supported by the vast majority, if not all, of the observations on these drugs made in the past.

Cytotoxicity to macrophages of tetrandrine, an antisilicosis alkaloid, accompanied by an overproduction of prostaglandins

Tetrandrine, an anti-inflammatory immunosuppressive bisbenzylisoquinoline alkaloid of Chinese herbal origin, is widely used to treat silicosis and interferes with the regulation of calcium in many cell types. We investigated its effect on the cellular integrity of macrophages and on their ability to generate prostaglandins and nitric oxide, mediators of inflammation with immunomodulatory roles. Tetrandrine at 10(-7) M to 10(-4) M caused dose- and time-dependent loss of cell viability of mouse peritoneal macrophages, guinea-pig alveolar macrophages and mouse macrophage-like J774 cells. Loss of viability (50%) occurred within 1-3 hr and required approximately 5 x 10(-6) M tetrandrine. Loss of macrophage viability after tetrandrine treatment was accompanied by the generation of large amounts of prostaglandin E2 (PGE2), to levels 285-877% of control. Coincubation with indomethacin abolished PGE2 generation, but did not prevent cell death. Tetrandrine did not cause generation of nitric oxide. Verapamil also reduced the viability of mouse peritoneal macrophages and J774 cells, but did not cause PGE2 overproduction, except at 10(-4) M in mouse peritoneal macrophages. In macrophages cultured with lipopolysaccharide and interferon-gamma to induce the generation of large amounts of both PGE2 and nitric oxide, tetrandrine reduced mediator release and their forming enzymes (cyclo-oxygenase-2 and inducible nitric oxide synthase), secondary to cytotoxicity. The predominant action of tetrandrine is to exert a cytotoxic effect on macrophages, perhaps by interfering with calcium homeostasis; this leads to overproduction of immunomodulatory but proinflammatory prostaglandin. This may be relevant to its protective actions in human fibrosing silicosis, in which there is alveolar macrophage involvement.

Environmental influences on fatty acid composition of membranes from autoimmune MRL lpr/lpr mice

We analyzed fatty acid make up of cells and organs from autoimmune and immunologically normal mice to determine whether intrinsic differences in composition might be associated with an inflammatory phenotype. Macrophages (MO) isolated from 4-6-week-old MRL lpr/lpr mice were cultured with phorbol ester (PMA), fibroblast growth factor-1 (FGF-1), fibroblast growth factor-2 (FGF-2) and medium control to determine whether these cell signals might induce membrane fatty acid changes. Individual phospholipid analysis showed 8.4- and 5.1-fold increases in phosphatidylcholine arachidonate (20:4) mole % over baseline values following culture with FGF-1 and FGF-2, respectively. Unfractionated analysis on kidney and liver extracts from 4-6 week MRL lpr/lpr, 16-20 week lpr and 12-20 week MRL +/-/+/- mice demonstrated no significant intrastrain fatty acid differences. Higher levels of 20:4 in 4-6 week lpr mice were noted compared to 16-20 week lpr or +/+ mice in kidney, and liver samples (P < 0.05). It is possible that membrane changes precipitated by microenvironmental cytokine concentrations may contribute to the expression of autoimmune disease in this model.

Composition of peritoneal macrophage membranes in autoimmune MRL lpr/lpr mice

Adult MRL lpr/lpr mice display phenotypic features that are consistent with both rheumatoid arthritis and systemic lupus erythematosus. Previous studies have reported that peritoneal macrophages harvested from this model have an increased propensity for both spontaneous and elicited release of prostaglandins and leukotrienes relative to immunologically normal control mice. To investigate whether one aspect of the differences in secretory potential between autoimmune and normal mice was at the level of increased substrate availability, gas chromatographic analysis of peritoneal macrophage membranes from autoimmune MRL lpr/lpr, young lpr, wild type +/+, and immunologically normal mice was done. The results demonstrate enrichment of arachidonate in adult lpr macrophage membranes in all major phospholipid classes relative to young lpr, +/+ and immunologically normal C3H/HeN mice. Similarly, there was an increased mole % of arachidonic acid in lpr mice relative to controls. Elevated membrane arachidonate may contribute to the increased propensity of autoimmune strains to participate in the inflammatory process.