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M Tsai

Publications and source records attributed to M Tsai.

At least 55 records · Page 3Linked to original sources
PubMed1993

Activation of MAP kinases, pp90rsk and pp70-S6 kinases in mouse mast cells by signaling through the c-kit receptor tyrosine kinase or Fc epsilon RI: rapamycin inhibits activation of pp70-S6 kinase and proliferation in mouse mast cells.

The high-affinity receptor for IgE, Fc epsilon RI, represents the major cell surface structure through which mast cells express immunologically specific secretory function. By contrast, the stem cell factor receptor (SCFR), which is encoded by c-kit, is essential for normal mast cell development. The signaling pathways initiated by the stimulation of mast cells through the Fc epsilon RI, which lacks intrinsic kinase activity, and the SCFR, a member of the receptor tyrosine kinase family, generally have been regarded to be distinct. We report here that mouse mast cells stimulated either with SCF or with IgE and specific antigen exhibit a remarkably similar pattern of activation of mitogen-activated protein kinases (MAPK), 90 kDa-S6 kinases (pp90rsk), and pp70-S6 kinases (pp70-S6K). These results indicate that all three families of protein kinases are associated with the cell surface receptor-dependent activation of secretion, as well as proliferation, in mast cells. We also show that the immunosuppressant rapamycin, but not FK506, can inhibit both SCF-dependent pp70-S6 kinase activation and SCF-dependent proliferation in mouse mast cells, without suppressing IgE- and antigen-dependent mediator release. These findings suggest that the activation of pp70-S6 kinase represents an important link in the stimulation of cell proliferation by SCF. Our results also indicate that the intracellular signaling pathways initiated by stimulation of mast cells through the Fc epsilon RI or the SCFR exhibit more overlap than has previously been appreciated.

Animals↗
PubMed1993

The c-kit receptor, stem cell factor, and mast cells. What each is teaching us about the others.

Many years ago, alert observers noticed among thousands of laboratory mice a few individuals that, unlike their littermates, exhibited areas of white spotting on their fur. No one could have predicted then that an effort to understand the basis for these abnormalities would ultimately contribute to the characterization of a receptor (c-kit) and a corresponding ligand (stem cell factor, SCF) that are critical not only to the migration and development of melanocytes, but also to hematopoiesis, gametogenesis, mast cell development, and, perhaps, development of the central nervous system. Nor could anyone have foretold then that this receptor and ligand would be shown to regulate the development of multiple distinct cellular lineages not only in mice, but also in humans and other primates, or that c-kit and its ligand would be found to influence the secretory function of cells bearing this receptor, as well as their development. Investigation of the effects of SCF on a single cell type, the mast cell, has produced the most complete picture of the spectrum of biological processes that can be regulated by interactions between c-kit and its ligand. This work shows that SCF critically regulates the migration and survival of mast cell precursors, promotes the proliferation of both immature and mature mast cells, enhances mast cell maturation, directly induces secretion of mast cell mediators, and can regulate the extent of mediator release in mast cells activated by IgE-dependent mechanisms. Indeed, SCF may well prove to be one of the most important of the factors influencing mast cell numbers, phenotype, and function in both health and disease. It now seems virtually certain that further studies of c-kit and SCF will produce important new insights into problems as diverse as the regulation of lineage commitment during normal hematopoiesis or the development and function of the central nervous system. And even though an effect on mast cell development was one of the last phenotypic abnormalities to be recognized in mice with mutations affecting the genes encoding c-kit or SCF, mast cells will continue to represent an important model system for analyzing the biology of c-kit and its ligand.

Animals↗
PubMed1992

Peroxynitrite-mediated tyrosine nitration catalyzed by superoxide dismutase.

Peroxynitrite (ONOO-), the reaction product of superoxide (O2-) and nitric oxide (NO), may be a major cytotoxic agent produced during inflammation, sepsis, and ischemia/reperfusion. Bovine Cu,Zn superoxide dismutase reacted with peroxynitrite to form a stable yellow protein-bound adduct identified as nitrotyrosine. The uv-visible spectrum of the peroxynitrite-modified superoxide dismutase was highly pH dependent, exhibiting a peak at 438 nm at alkaline pH that shifts to 356 nm at acidic pH. An equivalent uv-visible spectrum was obtained by Cu,Zn superoxide dismutase treated with tetranitromethane. The Raman spectrum of authentic nitrotyrosine was contained in the spectrum of peroxynitrite-modified Cu,Zn superoxide dismutase. The reaction was specific for peroxynitrite because no significant amounts of nitrotyrosine were formed with nitric oxide (NO), nitrogen dioxide (NO2), nitrite (NO2-), or nitrate (NO3-). Removal of the copper from the Cu,Zn superoxide dismutase prevented formation of nitrotyrosine by peroxynitrite. The mechanism appears to involve peroxynitrite initially reacting with the active site copper to form an intermediate with the reactivity of nitronium ion (NO2+), which then nitrates tyrosine on a second molecule of superoxide dismutase. In the absence of exogenous phenolics, the rate of nitration of tyrosine followed second-order kinetics with respect to Cu,Zn superoxide dismutase concentration, proceeding at a rate of 1.0 +/- 0.1 M-1.s-1. Peroxynitrite-mediated nitration of tyrosine was also observed with the Mn and Fe superoxide dismutases as well as other copper-containing proteins.

Animals↗
PubMed1992

Kinetics of superoxide dismutase- and iron-catalyzed nitration of phenolics by peroxynitrite.

Superoxide dismutase and Fe3+EDTA catalyzed the nitration by peroxynitrite (ONOO-) of a wide range of phenolics including tyrosine in proteins. Nitration was not mediated by a free radical mechanism because hydroxyl radical scavengers did not reduce either superoxide dismutase or Fe3+EDTA-catalyzed nitration and nitrogen dioxide was not a significant product from either catalyst. Rather, metal ions appear to catalyze the heterolytic cleavage of peroxynitrite to form a nitronium-like species (NO2+). The calculated energy for separating peroxynitrous acid into hydroxide ion and nitronium ion is 13 kcal.mol-1 at pH 7.0. Fe3+EDTA catalyzed nitration with an activation energy of 12 kcal.mol-1 at a rate of 5700 M-1.s-1 at 37 degrees C and pH 7.5. The reaction rate of peroxynitrite with bovine Cu,Zn superoxide dismutase was 10(5) M-1.s-1 at low superoxide dismutase concentrations, but the rate of nitration became independent of superoxide dismutase concentration above 10 microM with only 9% of added peroxynitrite yielding nitrophenol. We propose that peroxynitrite anion is more stable in the cis conformation, whereas only a higher energy species in the trans conformation can fit in the active site of Cu,Zn superoxide dismutase. At high superoxide dismutase concentrations, phenolic nitration may be limited by the rate of isomerization from the cis to trans conformations of peroxynitrite as well as by competing pathways for peroxynitrite decomposition. In contrast, Fe3+EDTA appears to react directly with the cis anion, resulting in greater nitration yields.

Animals↗
PubMed1992

The rat c-kit ligand, stem cell factor, induces c-kit receptor-dependent mouse mast cell activation in vivo. Evidence that signaling through the c-kit receptor can induce expression of cellular function.

Interactions between products of the mouse W locus, which encodes the c-kit tyrosine kinase receptor, and the Sl locus, which encodes a ligand for c-kit receptor, which we have designated stem cell factor (SCF), have a critical role in the development of mast cells. Mice homozygous for mutations at either locus exhibit several phenotypic abnormalities including a virtual absence of mast cells. Moreover, the c-kit ligand SCF can induce the proliferation and maturation of normal mast cells in vitro or in vivo, and also can result in repair of the mast cell deficiency of Sl/Sld mice in vivo. We now report that administration of SCF intradermally in vivo results in dermal mast cell activation and a mast cell-dependent acute inflammatory response. This effect is c-kit receptor dependent, in that it is not observed when SCF is administered to mice containing dermal mast cells expressing functionally inactive c-kit receptors, is observed with both glycosylated and nonglycosylated forms of SCF, and occurs at doses of SCF at least 10-fold lower on a molar basis than the minimally effective dose of the classical dermal mast cell-activating agent substance P. These findings represent the first demonstration in vivo that a c-kit ligand can result in the functional activation of any cellular lineage expressing the c-kit receptor, and suggest that interactions between the c-kit receptor and its ligand may influence mast cell biology through complex effects on proliferation, maturation, and function.

Animals↗
PubMed1992

Analyzing mast cell development and function using mice carrying mutations at W/c-kit or Sl/MGF (SCF) loci.

Mast cells have been implicated in a wide variety of biological responses, but identifying the nature and importance of the mast cell's specific contributions to these reactions has been difficult. W/Wv mice have mutations affecting the c-kit tyrosine kinase receptor which is encoded at the W locus and which is necessary for normal mast cell development. In W/Wv mice, the cells which ordinarily give rise to normal mast cell populations do not adequately respond to a major migration, survival, proliferation and maturation factor expressed in the microenvironments where mast cells ordinarily develop: the c-kit receptor ligand, SCF. As a result, W/Wv mice virtually lack tissue mast cells. However, adoptive transfer to W/Wv mice of immature mast cells derived in vitro from the bone marrow cells of the congenic normal (+/+) mice selectively repairs the mast cell deficiency of the W/Wv recipients. These "mast cell knock-in" mice can be used to analyze the expression of biological responses in tissues which differ only because they do or do not contain populations of mast cells. This approach permits identification and quantification of the specific contributions of the mast cell to biological responses expressed in the skin, gastrointestinal tract and other anatomical sites, and also greatly facilitates analysis of the mechanisms by which mast cells influence these responses.

Animals↗
PubMed1991

Induction of mast cell proliferation, maturation, and heparin synthesis by the rat c-kit ligand, stem cell factor.

We investigated the effects of a newly recognized multifunctional growth factor, the c-kit ligand stem cell factor (SCF), on mouse mast cell proliferation and phenotype. Recombinant rat SCF164 (rrSCF164) induced the development of large numbers of dermal mast cells in normal mice in vivo. Many of these mast cells had features of "connective tissue-type mast cells" (CTMC), in that they were reactive both with the heparin-binding fluorescent dye berberine sulfate and with safranin. In vitro, rrSCF164 induced the proliferation of cloned interleukin 3 (IL-3)-dependent mouse mast cells and primary populations of IL-3-dependent, bone marrow-derived cultured mast cells (BMCMC), which represent immature mast cells, and purified peritoneal mast cells, which represent a type of mature CTMC. BMCMC maintained in rrSCF164 not only proliferated but also matured. Prior to exposure to rrSCF164, the BMCMC were alcian blue positive, safranin negative, and berberine sulfate negative; had a histamine content of 0.08 +/- 0.02 pg per cell; and incorporated [35S]sulfate into chondroitin sulfates. After 4 wk in rrSCF164, the BMCMC were predominantly safranin positive and berberine sulfate positive, had a histamine content of 2.23 +/- 0.39 pg per cell, and synthesized 35S-labeled proteoglycans that included substantial amounts (41-70%) of [35S]heparin. These findings identify SCF as a single cytokine that can induce immature, IL-3-dependent mast cells to mature and to acquire multiple characteristics of CTMC. These findings also directly demonstrate that SCF can regulate the development of a cellular lineage expressing c-kit through effects on both proliferation and maturation.

Animals↗
PubMed1991

The rat c-kit ligand, stem cell factor, induces the development of connective tissue-type and mucosal mast cells in vivo. Analysis by anatomical distribution, histochemistry, and protease phenotype.

Mast cell development is a complex process that results in the appearance of phenotypically distinct populations of mast cells in different anatomical sites. Mice homozygous for mutations at the W or S1 locus exhibit several phenotypic abnormalities, including a virtual absence of mast cells in all organs and tissues. Recent work indicates that W encodes the c-kit tyrosine kinase receptor, whereas S1 encodes a c-kit ligand that we have designated stem cell factor (SCF). Recombinant or purified natural forms of the c-kit ligand induce proliferation of certain mast cell populations in vitro, and injection of recombinant SCF permits mast cells to develop in mast cell-deficient WCB6F1-S1/S1d mice. However, the effects of SCF on mast cell proliferation, maturation, and phenotype in normal mice in vivo were not investigated. We now report that local administration of SCF in vivo promotes the development of connective tissue-type mast cells (CTMC) in the skin of mice and that systemic administration of SCF induces the development of both CTMC and mucosal mast cells (MMC) in rats. Rats treated with SCF also develop significantly increased tissue levels of specific rat mast cell proteases (RMCP) characteristic of either CTMC (RMCP I) or MMC (RMCP II). These findings demonstrate that SCF can induce the expansion of both CTMC and MMC populations in vivo and show that SCF can regulate at least one cellular lineage that expresses c-kit, the mast cell, through complex effects on proliferation and maturation.

Animals↗
PubMed1991

Long-term histologic and electrophysiologic evaluation of the alloy retinal tack.

The retinal tack is a useful adjunctive instrument in the repair of complicated retinal detachments. To examine the tissue response of chronically implanted alloy tacks, we implanted a series of tacks into rabbit eyes. Their effects were observed at 1 and 4 weeks, at 6 months, and at 2.5 years after insertion. Our observations indicate that the histology and electrophysiology of the retina was generally not affected. All tacks were surrounded by connective and/or glial tissue scar and induced firm retinal adherence. The retinal architecture was normal within 1 mm of the scar, indicating that these alloy tacks do not cause tissue damage outside the immediate area of the wound, even when left in place over a period of 2 years.

Alloys↗
PubMed1991

The effects of Carbogen, carbon dioxide, and oxygen on noise-induced hearing loss.

An investigation into the effect of Carbogen (95% O2/5% CO2), 5% CO2/air, and 100% oxygen on cochlear threshold shifts caused by noise was undertaken. Five groups of eight pigmented guinea pigs were exposed to 105 dB broad band noise for 6 h per day for five consecutive days with each group receiving the various gaseous mixtures either during noise exposure or for 1 h immediately after noise exposure. A control group received the same noise exposure but respired air. Auditory threshold shifts, as measured by the auditory evoked brainstem response, were measured at 2,4,8,12,16, 20 and 24 kHz. Recordings were taken pre-exposure and at Day 1, 3, 5, and Weeks 2 and 3 after noise exposure. Carbogen, given during noise exposure, resulted in a trend toward less post noise exposure threshold shift (as compared to controls) which reached statistical significance by Week 3 at all frequencies except 2 and 20 kHz. Subjects given Carbogen after exposure also showed a general trend toward decreased noise induced threshold shifts, as compared to controls, but this was not statistically significant. The mixture of 5% CO2/air given during noise exposure yielded no difference in threshold shifts as compared to controls. When 100% oxygen was administered during noise exposure, a marked decrease in noise induced threshold shifts could be seen as compared to controls, with differences reaching statistical significance by day 5 at most frequencies. These results indicate that oxygen (i.e. cochlear-oxygenation) is a more important factor than CO2 (i.e., as a vasodilator) in protection of the cochlea from noise induced damage.

Animals↗