Essential Roles of Natural Products and Gaseous Mediators on Neuronal Cell Death or Survival

Although precise cellular and molecular mechanisms underlying neurodegeneration still remain enigmatic, key factors associated with degenerative disorders, such as glutamate toxicity and oxidative stress, have been recently identified. Accordingly, there has been growing interest in examining the effects of exogenous and endogenous molecules on neuroprotection and neurodegeneration. In this paper, we review recent studies on neuroprotective and/or neurodegenerative effects of natural products, such as caffeic acid and chlorogenic acid, and gaseous mediators, including hydrogen sulfide and nitric oxide. Furthermore, possible molecular mechanisms of these molecules in relation to glutamate signals are discussed. Insight into the pathophysiological role of these molecules will make progress in our understanding of molecular mechanisms underlying neurodegenerative diseases, and is expected to lead to potential therapeutic approaches

Temporal switching and cell-to-cell variability in Ca2+ release activity in mammalian cells

Genetically identical cells in a uniform external environment can exhibit different phenotypes, which are often masked by conventional measurements that average over cell populations. Although most studies on this topic have used microorganisms, differentiated mammalian cells have rarely been explored. Here, we report that only approximately 40% of clonal human embryonic kidney 293 cells respond with an intracellular Ca2+ increase when ryanodine receptor Ca2+ release channels in the endoplasmic reticulum are maximally activated by caffeine. On the other hand, the expression levels of ryanodine receptor showed a unimodal distribution. We showed that the difference in the caffeine sensitivity depends on a critical balance between Ca2+ release and Ca2+ uptake activities, which is amplified by the regenerative nature of the Ca2+ release mechanism. Furthermore, individual cells switched between the caffeine-sensitive and caffeine-insensitive states with an average transition time of approximately 65 h, suggestive of temporal fluctuation in endogenous protein expression levels associated with caffeine response. These results suggest the significance of regenerative mechanisms that amplify protein expression noise and induce cell-to-cell phenotypic variation in mammalian cells

The Role of a Brain-specific Splice Variant of Ryanodine Receptor Type 1

The ryanodine receptor type 1 (RyR1) is capable of homotetrameric assembly to form a Ca2+ release channel at intracellular Ca2+ storage sites such as endoplasmic reticulum (ER). The mRNA transcript encoding full-length RyR1 is approximately 16kb and is mainly distributed in excitable cells. A 2.4-kb mRNA splice variant from the 3\u27-terminal region of the RyR1 gene coexists specifically in brain together with the full-length form, although the functions of this brain-specific splice variant remain unclear. To investigate the short form of RyR1 in intracellular Ca2+ signaling in brain at the cellular level, we established an experimental system whereby the green fluorescent protein (GFP) -tagged brain-specific variant of RyR1 is coexpressed with the full-length protein in the same cell. Both forms of RyR1 were localized in the ER. Caffeine-induced Ca2+-release activities in cells expressing both the brain-specific and full-length RyR1 were reduced compared to cells expressing only the full-length form of RyR1. These results suggested that coexpression of the brain-specific splice variant of RyR1 with its full-length counterpart modulates intracellular Ca2+ signaling by acting as a dominant-negative subunit of the Ca2+ release channel in a tissue-specific fashion

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1.平均栄養摂取量は,19歳女子普通労作の栄養所要量と比較すると,ビタミンC以外は不足の状態であり,特にカルシウムの不足が目立った。また摂取栄養量には個人差がかなりみられ所要量の±10%以内の者は,エネルギーにおいては36.8%,脂質においてはわずか21.1%であった。 2.朝食・昼食・夕食・間食における栄養摂取量の比率においては,間食の占める割合が比較的多い傾向にあり,これは女子短大生の特徴といえる。 3.栄養比率については,エネルギーの栄養素別摂取構成比は,たんぱく質14.8%,脂質26.9%,糖質58.3%であり,厚生省の示している適正比率目標にほぼ一致していた。また動物性たんぱく質比は50%,糖質エネルギー比は45.6%脂質エネルギーは27.2%であり,これらの比率も適当であると思われる。しかし個人的には問題のある者もかなりみられた。 4.食品群別摂取量については,高居ら^7)の示す食糧構成案と比較すると,パン類・めん類・いも類・菓子・獣鳥肉類・卵類においては充足されているが,他の食品群は不足し,特に米類・砂糖・みその不足が目立った。 5.主食の種類は,その頻度において全体として米飯を主体とする傾向にあるが,朝食ではパンが,昼食では麺類が比較的多く摂られていた。 6.外食の状況は,その頻度においては,昼食・夕食・朝食の順であり,その主食の種類は,全体では米飯・パン・麺類がはぼ同数であったが朝食ではパンが,夕食では米飯が多かった。 7.欠食状況は,朝食では34.2%,昼食では,23.7%,夕食では7.9%の者が欠食しており,国民栄養調査(昭和56年度15～20歳)^2)と比較するといずれも高い比率であった。また朝食における欠食が最も多く,朝食を5日間連続欠食した者も2.6%あった。なお1日に1回以上欠食した者としなかった者とでは,エネルギー摂取量に250kcalの差がみられた。 8.食品添加物の1人1日当たりの摂取品目は10～69品目,平均43品目であり,摂取量は平均4.4gであった。これは谷村^15),藤井ら^16)の述べているものと近い数値であった。以上のごとく,栄養摂取量の不足や食品の摂り方における量不足と偏り,間食の摂り過ぎや欠食の多いことなど,問題点が多くみられた。従ってこれらのことがらについてきめ細かい指導の必要性を強く感じた

Nitric oxide-induced calcium release: activation of type 1 ryanodine receptor by endogenous nitric oxide.

Ryanodine receptors (RyRs), located in the sarcoplasmic/endoplasmic reticulum (SR/ER) membrane, are required for intracellular Ca2+ release that is involved in a wide range of cellular functions. In addition to Ca2+-induced Ca2+ release in cardiac cells and voltage-induced Ca2+ release in skeletal muscle cells, we recently identified another mode of intracellular Ca2+ mobilization mediated by RyR, i.e., nitric oxide-induced Ca2+ release (NICR), in cerebellar Purkinje cells. NICR is evoked by neuronal activity, is dependent on S-nitrosylation of type 1 RyR (RyR1) and is involved in the induction of long-term potentiation (LTP) of cerebellar synapses. In this addendum, we examined whether peroxynitrite, which is produced by the reaction of nitric oxide with superoxide, may also have an effect on the Ca2+ release via RyR1 and the cerebellar LTP. We found that scavengers of peroxynitrite have no significant effect either on the Ca2+ release via RyR1 or on the cerebellar LTP. We also found that an application of a high concentration of peroxynitrite does not reproduce neuronal activity-dependent Ca2+ release in Purkinje cells. These results support that NICR is induced by endogenous nitric oxide produced by neuronal activity through S-nitrosylation of RyR1