Tatsuya Ishikawa

Voltage-dependent N-type Ca2+ channels in endothelial cells contribute to oxidative stress-related endothelial dysfunction induced by angiotensin II in mice

N-type voltage-dependent Ca(2+)channels (VDCCs), expressed predominantly in the nervous system, play pivotal roles in sympathetic regulation of the circulatory system. Although N-type VDCCs are also reportedly expressed in the vasculature, their pathophysiological role is obscure. We demonstrated that oxidative stress-related endothelial dysfunction induced by angiotensin (Ang) II is suppressed in mice lacking the N-type VDCC α1B subunit (Cav 2.2). Impairment of endothelium-dependent relaxation of the thoracic aorta observed following Ang II treatment in wild-type (WT) mice was significantly attenuated in the Ang II-treated Cav 2.2-deficient mice, despite the comparable increase of the blood pressure in the two groups of mice. The thoracic aorta of the Cav 2.2-deficient mice showed a smaller positive area of oxidative stress markers as compared to the WT mice. The Ang II-induced endothelial dysfunction was also suppressed by cilnidipine, an L/N-type VDCC blocker, but not by amlodipine, an L-type VDCC blocker; however, this unique effect of cilnidipine was completely abolished in the Cav 2.2-deficient mice. Furthermore, selective inhibition of N-type VDCCs by ω-conotoxin GVIA dramatically suppressed the production of reactive oxygen species (ROS) as well as agonist-induced Ca(2+) influx in the vascular endothelial cells. These results suggest that N-type VDCCs expressed in the vascular endothelial cells contribute to ROS production and endothelial dysfunction observed in Ang II-treated hypertensive mice.

TRPC6 counteracts TRPC3-Nox2 protein complex leading to attenuation of hyperglycemia-induced heart failure in mice

Excess production of reactive oxygen species (ROS) caused by hyperglycemia is a major risk factor for heart failure. We previously reported that transient receptor potential canonical 3 (TRPC3) channel mediates pressure overload-induced maladaptive cardiac fibrosis by forming stably functional complex with NADPH oxidase 2 (Nox2). Although TRPC3 has been long suggested to form hetero-multimer channels with TRPC6 and function as diacylglycerol-activated cation channels coordinately, the role of TRPC6 in heart is still obscure. We here demonstrated that deletion of TRPC6 had no impact on pressure overload-induced heart failure despite inhibiting interstitial fibrosis in mice. TRPC6-deficient mouse hearts 1 week after transverse aortic constriction showed comparable increases in fibrotic gene expressions and ROS production but promoted inductions of inflammatory cytokines, compared to wild type hearts. Treatment of TRPC6-deficient mice with streptozotocin caused severe reduction of cardiac contractility with enhancing urinary and cardiac lipid peroxide levels, compared to wild type and TRPC3-deficient mice. Knockdown of TRPC6, but not TRPC3, enhanced basal expression levels of cytokines in rat cardiomyocytes. TRPC6 could interact with Nox2, but the abundance of TRPC6 was inversely correlated with that of Nox2. These results strongly suggest that Nox2 destabilization through disrupting TRPC3-Nox2 complex underlies attenuation of hyperglycemia-induced heart failure by TRPC6.

Eco-pharma of approved drug focused on mitochondria fission

ミ ト コ ン ド リ ア 品 質 管 理 の 生 物 学 的 理 解 と そ の 医 療 応 用 4 要約:医薬品の開発研究は,新たな薬剤を生み出す創 薬研究と既存の薬剤の新たな作用を見出し応用する育 薬研究に分けられる.創薬標的はますます複雑化の一 途を辿り,新薬創出の研究に必要とされる時間とコス トも膨れ上がっている.新薬開発に比べて既承認薬は ヒトでの安全性,薬物動態が確立されており,他の疾 患への治療薬として適応するにあたって大幅な時間と コストの削減が可能となる.このような新しい医薬品 研究のあり方は「エコファーマ(またはドラッグ・リ ポジショニング)」として提唱されている.ミトコン ドリアは分裂と融合を動的に制御することでその品質 を維持している.ミトコンドリアの機能異常は様々な 疾患の原因となるため,その品質管理が新しい治療標 的として注目されている.我々は心筋梗塞後に心筋が 早期老化を引き起こす前段階において,ミトコンドリ ア過剰分裂が起こること,およびこの原因が低酸素に 依存したミトコンドリア分裂促進 GTP結合タンパク 質 dynamin-related protein 1(Drp1)の活性化にあるこ とを見出した.ラット新生児心筋細胞において,低酸 素/再酸素化刺激は心筋細胞の早期老化を引き起こし, 低酸素誘発性のミトコンドリア分裂を阻害することで 再酸素化後の心筋早期老化が抑制された.低酸素刺激 によるミトコンドリア分裂を阻害しうる既承認薬のス クリーニングを行った結果,ジヒドロピリジン系Ca チャネル阻害薬であるシルニジピン(cilnidipine: CIL)がミトコンドリア分裂を抑制することを見出し た.CILは Caチャネル阻害作用と無関係に Drp1 活 性化を抑制し,心筋老化を抑制した.以上の結果は, CILがミトコンドリア過剰分裂に起因する様々な疾患 の治療薬に適応拡大できることを強く示している. 1. はじめに