Michael A. Beaven

Resveratrol ameliorates aging-related metabolic phenotypes by inhibiting cAMP phosphodiesterases

Resveratrol, a polyphenol in red wine, has been reported as a calorie restriction mimetic with potential antiaging and antidiabetogenic properties. It is widely consumed as a nutritional supplement, but its mechanism of action remains a mystery. Here, we report that the metabolic effects of resveratrol result from competitive inhibition of cAMP-degrading phosphodiesterases, leading to elevated cAMP levels. The resulting activation of Epac1, a cAMP effector protein, increases intracellular Ca(2+) levels and activates the CamKKβ-AMPK pathway via phospholipase C and the ryanodine receptor Ca(2+)-release channel. As a consequence, resveratrol increases NAD(+) and the activity of Sirt1. Inhibiting PDE4 with rolipram reproduces all of the metabolic benefits of resveratrol, including prevention of diet-induced obesity and an increase in mitochondrial function, physical stamina, and glucose tolerance in mice. Therefore, administration of PDE4 inhibitors may also protect against and ameliorate the symptoms of metabolic diseases associated with aging.

Characterization of novel stem cell factor responsive human mast cell lines LAD 1 and 2 established from a patient with mast cell sarcoma/leukemia; activation following aggregation of FcεRI or FcγRI

Two novel stem cell factor (SCF) dependent human mast cell lines, designated LAD 1 and 2, were established from bone marrow aspirates from a patient with mast cell sarcoma/leukemia. LAD 1 and 2 cells have the ultrastructural features of human mast cells, and express FcepsilonRI, CD4, 9, 13, 14, 22, 31, 32, 45, 64, 71, 103, 117, 132, CXCR4 (CD184), CCR5 (CD195); and intracytoplasmic histamine, tryptase and chymase. LAD 1 and 2 do not exhibit activating mutations at codon 816 of c-kit. Both LAD 1 and 2 release beta-hexosaminidase following FcepsilonRI or FcgammaRI aggregation. The availability of these cell lines offers an unparalleled circumstance to examine the biology of human mast cells.

Role of ABCC1 in export of sphingosine-1-phosphate from mast cells

Mast cells play a pivotal role in inflammatory and immediate-type allergic reactions by secreting a variety of potent inflammatory mediators, including sphingosine-1-phosphate (S1P). However, it is not known how S1P is released from cells. Here, we report that S1P is exported from mast cells independently of their degranulation and demonstrate that it is mediated by ATP binding cassette (ABC) transporters. Constitutive and antigen-stimulated S1P release was inhibited by MK571, an inhibitor of ABCC1 (MRP1), but not by inhibitors of ABCB1 (MDR-1, P-glycoprotein). Moreover, down-regulation of ABCC1 with small interfering RNA, which decreased its cell surface expression, markedly reduced S1P export from both rat RBL-2H3 and human LAD2 mast cells. Transport of S1P by ABCC1 influenced migration of mast cells toward antigen but not degranulation. These findings have important implications for S1P functions in mast cell-mediated immune responses.

Modification of the enzymatic isotopic assay of histamine and its application to measurement of histamine in tissues, serum and urine.

Abstract A modified enzymatic isotopic assay for histamine in tissue homogenates, serum and urine is described. The assay is based upon that of Snyder et al.1 in which histamine is converted to [14C]methylhistamine by incubation with histamine-N-methyltransferase and S-adenosylmethionine-[14C]methyl but is modified to make the formation and recovery of [14C]-methylhistamine quantitative and to reduce the extraction of other 14C-containing material. The modifications enhance the sensitivity of the assay to 0.1 ng histamine and permit the simultaneous measurement of as many as 80 to 100 samples. The assay is particularly useful for determining the histamine content in tissues with low histamine levels where the fluorometric assay of Shore et al.2 gives spuriously high results. The enzymatic assay also has the advantage that histamine can be measured directly in tissue homogenates, plasma, serum, and urine without the need for prior extraction of the histamine. Various amounts of histamine were detected in human tumors and normal tissues but none (less than 0.5 ng/ml) in human serum. Normal human urinary histamine excretion averaged 16 ± 14 (± SD) μg histamine/24 h.

Increased sensitivity of the enzymatic isotopic assay of histamine: measurement of histamine in plasma and serum.

Abstract The use of rat kidney instead of guinea pig brain as the source of histamine- N -methyltransferase for the enzymatic assay of histamine was found to improve the sensitivity of the assay. A partially purified preparation (ammonium sulfate fractionation) of the kidney enzyme was 20- to 50-fold more active than the guinea pig preparation, and sufficient enzyme for 14,000 assays could be prepared from six rats. The kidney enzyme, unlike the guinea pig brain enzyme, was free of interfering enzyme activities and gave low values for assay blanks. The two enzymes otherwise had similar properties. The low blank values permitted direct measurement of histamine in normal plasma without the need to isolate and concentrate histamine from the sample. Plasma histamine levels in normal individuals ranged from 0.2-1.4 (mean 0.6, n = 19) ng/ml.

Mitogen-activated Protein (MAP) Kinase Regulates Production of Tumor Necrosis Factor-α and Release of Arachidonic Acid in Mast Cells INDICATIONS OF COMMUNICATION BETWEEN p38 AND p42 MAP KINASES

Aggregation of the high affinity IgE receptor (FcεRI) in a mast cell line resulted in activation of the p42 and the stress-activated p38 mitogen-activated protein (MAP) kinases. Selective inhibition of these respective kinases with PD 098059 and SB 203580 indicated that p42 MAP kinase, but not p38 MAP kinase, contributed to the production of the cytokine, tumor necrosis factor-α, and the release of arachidonic acid in these cells. Neither kinase, however, was essential for FcεRI-mediated degranulation or constitutive production of tumor growth factor-β. Studies with SB 203580 and the p38 MAP kinase activator anisomycin also revealed that p38 MAP kinase negatively regulated activation of p42 MAP kinase and the responses mediated by this kinase.

In vivo studies of mediator release in cold urticaria and cholinergic urticaria

Six patients with cold urticaria were found to possess elevated plasma histamine levels after cold challenge by placing one hand in ice water for 4 minutes. A single patient became hypotensive during the procedure and had a level of 260 ng/ml. histamine in the venous effluent from his hand. No elevation of plasma serotonin or bradykinin was observed. Two patients with cholinergic urticaria possessed elevated plasma histamine levels during and after vigorous exercise for 10 minutes; these patients also gave a positive test for vibration-induced angioedema. A single patient with cholinergic urticaria possessed elevated baseline serotonin levels and elevated levels during and after exercise but no elevation of plasma histamine or bradykinin. The results suggest that histamine is the major mediator of urticaria and hypotension in cold urticaria. Histamine also appears to be released coincident with the development of urticaria in some patients with cholinergic urticaria, while elevated serotonin levels in a single atypical patient suggest that a subpopulation of patients with cholinergic urticaria possess a different pathogenesis.

Variable content of histaminase, L-dopa decarboxylase and calcitonin in small-cell carcinoma of the lung. Biologic and clinical implications.

To ascertain whether the content of endocrine markers is constant in small-cell carcinoma of the lung, levels of three markers of medullary thyroid carcinoma were studied in this tumor. Histaminase was increased in six of six primary tumors (three to 14,000 times), L-dopa decarboxylase in four of six (six to 30 times), and calcitonin in one of one (eight times) over levels in adjacent lung. Marker levels in mediastinal metastases reflected those in primary tumors in four of five patients. However, in four of seven, multiple hepatic metastases contained low to absent levels despite simultaneously high values in chest lesions. Immunohistochemical studies of histaminase revealed that within each primary tumor different cells contained different amounts of the enzyme. Since marker content varied between tumor cells, between primary tumors and between metastases in individual patients we conclude that circulating levels of these three markers cannot be expected necessarily to mirror tumor burden in patients with small-cell lung tumors.

Our perception of the mast cell from Paul Ehrlich to now

Just over a century ago Paul Ehrlich received the Nobel Prize for his studies of immunity. This review describes one of his legacies, the histochemical description of the mast cell, and the research that has ensued since then. After a long period of largely descriptive studies, which revealed little about the biological role of the mast cell, the field was galvanized in the 1950s by the recognition that the mast cell was the main repository of histamine and a key participant in anaphylactic reactions. Although the mast cell was long‐viewed in these terms, recent research has now shown that the mast cell also plays a key role in innate and adaptive immune responses, autoimmune disease, and possibly tissue homeostasis by virtue of its expression of a diverse array of receptors and biologically active products. In addition, the responsiveness of mast cells to immunological and pathological stimulants is highly modulated by the tissue cytokine environment and by synergistic, or inhibitory, interactions among the various mast cell receptor systems. This once enigmatic cell of Paul Ehrlich has proved to be both adaptable and multifunctional.

Alteration of tumor growth by aspirin and indomethacin: studies with two transplantable tumors in mouse.

Oral daily administration of aspirin or indomethacin retarded growth of experimental tumors in mouse. Aspirin treatment, 150 mg/kg twice daily, inhibited growth of a transplantable mast-cell ascites tumor (P815) by 39-43% (p less than 0.001) and of a s.c. transplanted Lewis lung carcinoma by 52% (p less than 0.025) without adversely affecting body growth. The total serotonin, histamine and histidine decarboxylase content of the ascites tumor was also reduced as was the urinary excretion of the amines. Treatment with 3 and 5 mg/kg indomethacin resulted in 40% (p less than 0.01) and 80% (p less than 0.001) reduction, respectively, in ascites tumor growth. With the higher dose of indomethacin, no tumor was observed in half of the animals inoculated with tumor, although signs of indomethacin toxicity (reduced body growth, gastric lesion) was evident in the animals.