Agonist/Inosital Trisphosphate-Induced Release of Calcium from Murine Keratinocytes: A Possible Link with Keratinocyte Differentiation

Extracellular calcium concentrations markedly affect the pattern of proliferation and differentiation in cultured keratinocytes. When medium contains 0.1 mM calcium or above, the cells lose their proliferative ability, rapidly stratify, and terminally differentiate. Because 1,25(OH)2D3 (a modulator of Ca++ homeostasis) enhances the differentiation of keratinocytes, we investigated whether a link exists between 1 ,25(OH)2D3-induced release of inositol-1,4,5-trisphosphate (Ins(1,4,5)P3) from Ptdlns 4,5-P2 and intracellular calcium [Ca++]i release from keratinocytes. Specifically, primary culture of keratinocytes were loaded with fluorescence dye Fura-2AM (10 μM) and changes in fluorescence intensity were monitored at the excitation wavelengths of 340 and 380 nm and emission wavelength of 505 nm. Additions of two agonists, 1,25(OH)2D3 (1.2 × 10-9 M) and 13-Cis retinoic acid (0.2 × 10-9 M), to dye-loaded keratinocytes induced rapid release of [Ca++]i, respectively, followed by gradual return to the prestimulated state. Addition of Ins(1,4,5)P3 (10) to saponin-treated (leaky) keratinocytes also resulted in a rapid release of [Ca]. In contrast, the addition of inositrol-1,3,4,5-tetrakisphosphate. Ins(1,3,4,5)P at similar concentration exerted negligible effect. Taken together, these results support the view that 1,25(OH)2D3-induced [Ca++]i release in keratinocytes may be via the Ins(1,4,5)P3 induced early release of intracellular [Ca++]. This may explain, at least in part, 1,25(Oh)2D3-enhanced keratinocyte differentiatin

Effects Of Retinoic Acid On Prostaglandin Biosynthesis In Guinea-Pig Skin

Topical application of retinoic acid on guinea-pig skin resulted within 70 hours in erythema with a concomitant elevation of endogenous prostaglandin E2 (PGE2) in the treated areas of the skin. Prolonged daily treatment resulted in the development of severe scaly dermatoses and a corresponding decrease in the level of PGE2 in the skin. Examination of retinoic acid effects on the in vitro biosynthesis of PGE2 from arachidonic acid by extracts from guinea-pig skin and sheep vesicular gland demonstrated that retinoic acid inhibits prostaglandin synthesis in a concentration and time-dependent manner. These results indicate that retinoic acid may exert a regulatory role on prostaglandin biosynthesis in the skin

Dietary Supplementation with Ethyl Ester Concentrates of Fish Oil (n-3) and Borage Oil (n-6) Polyunsaturated Fatty Acids Induces Epidermal Generation of Local Putative Anti-Inflammatory Metabolites

Clinical reports have attributed the amelioration of chronic inflammatory skin disorders to the presence of certain polyunsaturated fatty acids (PUFA) in dietary oils. To test the hypothesis of a local modulatory effect of these PUFA in the epidermis, the basal diet of normal guinea pigs was supplemented with ethyl esters of either fish oil [rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] or borage oi1 [rich in gamma-linolenic acid (GLA)]. Our data demonstrated that dietary oils influence the distribution of PUFA in epidermal phospholipids and the epidermal levels of PUFA-derived hydroxy fatty acids. Specifically, animals supplemented with ethyl esters of fish oil markedly incorporated EPA and DHA into epidermal phospholipids, which paralleled the epidermal accumulation of 1 5-hydroxyeicosapentaenoic acid (15-HEPE) and 17-hydroxydocosahexaenoic acid (17-HDoHE). Similarly, animals supplemented with esters of borage oil preferentially incorporated dihomogammalinolenic acid (DGLA), the epidermal elongase product of GLA, into the epidermal phospholipids, which also was ac- companied by epidermal accumulation of 15-hydroxyeicosatrienoic acid (15-HETrE). By factoring the epidermal levels of the 15-lipoxygenase products and their relative inhibitory potencies, we evolved a measure of the overall potential of dietary oils to exert local anti-inflammatory effect. For example, the leukotriene inhibition potentials (LIP) of both fish oil and borage oil were greatly enhanced when compared to controls. Thus, the altered profiles of epidermal 15-lipoxygenase products generated from particular dietary oils may be responsible, at least in part, for reported ameliorative effects of oils on chronic inflammatory skin disorders

Inhibition of sheep vesicular gland oxygenase by unsaturated fatty acids from skin of essential fatty acid deficient rats

Unsaturated fatty acids present in the lipids of essential fatty acid (EFA)-deficient rats were found to inhibit the oxygenase activity of sheep vesicular gland in an instantaneous, reversible manner. However, competitive inhibition by high levels of these acids cannot account fully for the reported loss of prostaglandin synthetic capacity of these EFA-deficient animals. A similar competitive inhibition pattern was observed with several anti-inflammatory drugs tested, whereas others also exhibited a time-dependent destructive effect on the oxygenase of the sheep vesicular gland. The relative effectiveness of these drugs in treating inflammations of the skin paralleled their effects on the vesicular gland oxygenase.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22411/1/0000861.pd

Suppression of Leukotriene B4 Generation by Ex-vivo Neutrophils Isolated from Asthma Patients on Dietary Supplementation with Gammalinolenic Acid-containing Borage Oil: Possible Implication in Asthma

Dietary gammalinolenic acid (GLA), a potent inhibitor of 5-lipoxygenase (5-LOX) and suppressor of leukotriene B(4) (LTB(4)), can attenuate the clinical course of rheumatoid arthritics, with negligible side effects. Since Zileuton, also an inhibitor of 5-LOX, attenuates asthma but with an undesirable side effect, we investigated whether dietary GLA would suppress biosynthesis of PMN-LTB(4) isolated from asthma patients and attenuate asthma. Twenty-four mild-moderate asthma patients (16–75 years) were randomized to receive either 2.0 g daily GLA (borage oil) or corn oil (placebo) for 12 months. Blood drawn at 3 months intervals was used to prepare sera for fatty acid analysis, PMNs for determining phospholipid fatty acids and for LTB4 generation. Patients were monitored by daily asthma scores, pulmonary function, and exhaled NO. Ingestion of daily GLA (i) increased DGLA (GLA metabolite) in PMN-phospholipids; (ii) increased generation of PMN-15-HETrE (5-LOX metabolite of DGLA). Increased PMN-DGLA/15-HETrE paralleled the decreased PMN generation of proinflammatory LTB(4). However, the suppression of PMN-LTB4 did not reveal statistically significant suppression of the asthma scores evaluated. Nonetheless, the study demonstrated dietary fatty acid modulation of endogenous inflammatory mediators without side effects and thus warrant further explorations into the roles of GLA at higher doses, leukotrienes and asthma

2001-480.jan

ABSTRACT. Objective. To investigate mechanisms responsible for increased thrombotic activity in systemic lupus erythematosus (SLE) associated with the antiphospholipid syndrome (APS). We had reported that anticardiolipin/ß 2 -glycoprotein I (aCL/ß 2 -GPI) complexes induce platelet overactivity resulting in excessive production of thromboxane A 2 (TXA 2 ). Presumably this occurs by decreased platelet cyclic AMP (cAMP) activity and results in increased platelet aggregation. Methods. We stimulated platelet intracellular cAMP generation with known cAMP agonists (dibutyryl cAMP, theophylline, and prostaglandin E 1 ) and measured aCL/ß 2 -GPI induced platelet TXB 2 production in vitro. Isolated human platelets were prelabeled with 14 C-arachidonic acid and then challenged with aCL/ß 2 -GPI in the presence or absence of cAMP-activating substances. The resulting 14 C labeled TXB 2 was quantified by thin layer chromatography and radioactive scanning. Results. We found a marked decrease in aCL/ß 2 -GPI induced platelet TXB 2 production by the cAMP agonists in a dose dependent manner. Conclusion. Our findings suggest the usefulness of cAMP agonists in the control of thrombosis in some patients with SLE and APS. (J Rheumatol 2003;30:55-9) Key Indexing Terms: ANTIPHOSPHOLIPID ANTIBODIES THROMBOXANE A 2 ANTIPHOSPHOLIPID SYNDROME PLATELETS Personal, non-commercial use only. The Journal of Rheumatolog

Induced rapid phospholipid methylation and arachidonic acid release by dimethyl sulfoxide-treated human promyelocytic leukemic HL-60 cells

The incubation of undifferentiated promyelocytic HL-60 cells with DMSO resulted in the rapid transmethylation of phosphatidyl-ethanolamine (PE) into phosphatidylcholine (PC) which was maximal at 60 secs. This rapid generation of PC was followed by a decrease of the methylated phospholipid and the release of arachidonic acid. Thus, the rapid DMSO-induced phospholipid methylation coupled with release of arachidonic acid (precursor for eicosanoids) prior to morphological evidence of cellular differentiation may represent early biochemical events which result in the generation of intracellular chemical signals which may program the promyelocytic cells into a differentiation mode