ジャーナルクラブ British J Pharmacol 2012. October Volume 167, Issue 3

総説　リゾフォスファチジル酸　LPAと炎症

You have free access to this contentLysophosphatidic acid in atherosclerotic diseases (pages 465–482)
Andreas Schober and Wolfgang Siess

Lysophosphatidic acid (LPA) is a potent bioactive phospholipid. As many other biological active lipids, LPA is an autacoid: it is formed locally on demand, and it acts locally near its site of synthesis. LPA has a plethora of biological activities on blood cells (platelets, monocytes) and cells of the vessel wall (endothelial cells, smooth muscle cells, macrophages) that are all key players in atherosclerotic and atherothrombotic processes. The specific cellular actions of LPA are determined by its multifaceted molecular structures, the expression of multiple G-protein coupled LPA receptors at the cell surface and their diverse coupling to intracellular signalling pathways. Numerous studies have now shown that LPA has thrombogenic and atherogenic actions. Here, we aim to provide a comprehensive, yet concise, thoughtful and critical review of this exciting research area and to pinpoint potential pharmacological targets for inhibiting thrombogenic and atherogenic activities of LPA. We hope that the review will serve to accelerate knowledge of basic and clinical science, and to foster drug development in the field of LPA and atherosclerotic/atherothrombotic diseases.


LPA-induced platelet signalling during platelet shape change：理解されている血小板内細胞内情報伝達レベル


LPA induces neointima formation after vascular injury：理解されている血管新生メカニズム

原著
１．関節炎マウスの大動脈はセロトニンによる収縮反応が悪い「炎症」と「再生」
Contractile, but not endothelial, dysfunction in early inflammatory arthritis: a possible role for matrix metalloproteinase-9 (pages 505–514)
SL Reynolds, AS Williams, H Williams, S Smale, HJ Stephenson, N Amos, SJ George, VB O'Donnell and D Lang

BACKGROUND AND PURPOSE Excess morbidity/mortality in rheumatoid arthritis (RA) is associated with increased incidence of cardiovascular disease. In this ‘proof-of-concept’ study, vascular function was characterized in the murine collagen-induced arthritis (mCIA) model, the benchmark choice for evaluation of the pathological processes and assessment of new therapies.

EXPERIMENTAL APPROACH Mice in the very early stages of arthritis development [and appropriate naïve (non-immunized) age-matched controls] were used in the study. Blood pressure was measured using tail cuff plethysmography. Vascular function in rings of isolated aorta was studied with isometric tension myography. Levels of NO metabolites (NOx), MMP-9 protein and IL-1β in plasma and MMP-9 protein in aortic homogenates were quantified.

KEY RESULTS Impaired vascular contractile responses in arthritis were unaffected by ex vivo inhibition of NOS (endothelial/neuronal and inducible) or COX activities. Endothelium-dependent and -independent relaxation, plasma NOx and blood pressure were unaffected by arthritis. Plasma and aortic homogenate MMP-9 protein levels were increased significantly in arthritis. Incubation of aortic tissues from naïve control animals with exogenous MMP-9 impaired subsequent contractile responses, mirroring that observed in arthritis. A role for IL-1β in perpetuating contractile dysfunction and increasing aortic MMP-9 was excluded.

CONCLUSIONS AND IMPLICATIONS These data identify for the first time a relationship between early arthritis and contractile dysfunction and a possible role for MMP-9 therein, in the absence of overt endothelial dysfunction or increased NO production. As such, MMP-9 may constitute a significant target for early intervention in RA patients with a view to decreasing risk of cardiovascular disease.

炎症期にIL-1β，回復期にMMP9の発現により，セロトニンの収縮反応が低下するという，タイムコース評価の難しい研究系です。

２．Epithelium-dependent modulation of responsiveness of airways from caveolin-1 knockout mice is mediated through cyclooxygenase-2 and 5-lipoxygenase (pages 548–560)
Pawan Sharma, Min H Ryu, Sujata Basu, Sarah A Maltby, Behzad Yeganeh, Mark M Mutawe, Richard W Mitchell and Andrew J Halayko
epartment of Internal Medicine, University of Manitoba, Winnipeg, MB, Canada



BACKGROUND AND PURPOSE Acute silencing of caveolin-1 (Cav-1) modulates receptor-mediated contraction of airway smooth muscle. Moreover, COX-2- and 5-lipoxygenase (5-LO)-derived prostaglandin and leukotriene biosynthesis can influence smooth muscle reactivity. COX-2 half-life can be prolonged through association with Cav-1. We suggested that lack of Cav-1 modulated levels of COX-2 which in turn modulated tracheal contraction, when arachidonic acid signalling was disturbed by inhibition of COX-2.

EXPERIMENTAL APPROACH Using tracheal rings from Cav-1 knockout (KO) and wild-type mice (B6129SF2/J), we measured isometric contractions to methacholine and used PCR, immunoblotting and immunohistology to monitor expression of relevant proteins.

KEY RESULTS Tracheal rings from Cav-1 KO and wild-type mice exhibited similar responses, but the COX-2 inhibitor, indomethacin, increased responses of tracheal rings from Cav-1 KO mice to methacholine. The phospholipase A2 inhibitor, eicosatetraynoic acid, which inhibits formation of both COX-2 and 5-LO metabolites, had no effect on wild-type or Cav-1 KO tissues. Indomethacin-mediated hyperreactivity was ablated by the LTD4 receptor antagonist (montelukast) and 5-LO inhibitor (zileuton). The potentiating effect of indomethacin on Cav-1 KO responses to methacholine was blocked by epithelial denudation. Immunoprecipitation showed that COX-2 binds Cav-1 in wild-type lungs. Immunoblotting and qPCR revealed elevated levels of COX-2 and 5-LO protein, but not COX-1, in Cav-1 KO tracheas, a feature that was prevented by removal of the epithelium.

CONCLUSION AND IMPLICATIONS The indomethacin-induced hypercontractility observed in Cav-1 KO tracheas was linked to increased expression of COX-2 and 5-LO, which probably enhanced arachidonic acid shunting and generation of pro-contractile leukotrienes when COX-2 was inhibited.


３．アデノシンに似ているコルディセピン
Blockade of adipocyte differentiation by cordycepin (pages 561–575)
Shuhei Takahashi, Minori Tamai, Shotaro Nakajima, Hironori Kato, Hisashi Johno, Tomoyuki Nakamura and Masanori Kitamura

BACKGROUND AND PURPOSE Cordyceps militaris has the potential to suppress differentiation of pre-adipocytes. However, the active entities in the extract and the underlying mechanisms of its action are not known. Hence, we investigated whether and how cordycepin (3′-deoxyadenosine), a constituent of C. militaris, inhibits adipogenesis.

EXPERIMENTAL APPROACH Differentiation of 3T3-L1 pre-adipocytes and pre-adipocytes in primary cultures was induced by Insulin, dexamethasone and IBMX, and these were used as in vitro models of adipogenesis. The effects of cordycepin on adipogenesis were examined with particular focus on the regulation of CCAAT/enhancer-binding protein β (C/EBPβ) and PPARγ.

KEY RESULTS Cordycepin suppressed the lipid accumulation and induction of adipogenic markers that occurred on differentiation of pre-adipocytes and also blocked the down-regulation of a pre-adipocyte marker. This anti-adipogenic effect was reversible and mediated by an adenosine transporter, but not A1, A2 or A3 adenosine receptors. This effect of cordycepin was not reproduced by other adenosine-related substances, including ATP, ADP and adenosine. Early induction of the adipogenic C/EBPβ–PPARγ pathway was suppressed by cordycepin. Blockade of mTORC1 via inhibition of PKB (Akt) and activation of AMP kinase was identified as the crucial upstream event targeted by cordycepin. In addition to its negative effect on adipogenesis, cordycepin suppressed lipid accumulation in mature adipocytes.

CONCLUSIONS AND IMPLICATIONS These results suggest that the anti-adipogenic effects of cordycepin occur through its intervention in the mTORC1-C/EBPβ–PPARγ pathway. Cordycepin, by blocking both adipogenesis and lipid accumulation, may have potential as a therapeutic agent for effective treatment of obesity and obesity-related disorders.

mTOR複合体1への作用が重要
１）コルディセピンは，「さなぎ」に含まれています。「さなぎ」の粉末は，腸粘膜新生を抑制，がん細胞増殖を抑制などの作用があるとされています。
２）PKB活性を阻害する可能性があり，mTORC1を抑制する作用があります。
３）コルディセピンは，C/EBP mRNAを低下させる可能性があります。

４．Toll-like receptor 4 knockout protects against anthrax lethal toxin-induced cardiac contractile dysfunction: role of autophagy (pages 612–626)
Machender R Kandadi, Arthur E Frankel and Jun Ren 　競合する研究内容

BACKGROUND AND PURPOSE Anthrax lethal toxin (LeTx) is known to induce circulatory shock and death, although the underlying mechanisms have not been elucidated. This study was designed to evaluate the role of toll-like receptor 4 (TLR4) in anthrax lethal toxin-induced cardiac contractile dysfunction.

EXPERIMENTAL APPROACH Wild-type (WT) and TLR4 knockout (TLR－/－) mice were challenged with lethal toxin (2 µg·g－1, i.p.), and cardiac function was assessed 18 h later using echocardiography and edge detection. Small interfering RNA (siRNA) was employed to knockdown TLR4 receptor or class III PI3K in H9C2 myoblasts. GFP–LC3 puncta was used to assess autophagosome formation. Western blot analysis was performed to evaluate autophagy (LC3, Becline-1, Agt5 and Agt7) and endoplasmic reticulum (ER) stress (BiP, eIF2α and calreticulin).

KEY RESULTS In WT mice, lethal toxin exposure induced cardiac contractile dysfunction, as evidenced by reduced fractional shortening, peak shortening, maximal velocity of shortening/re-lengthening, prolonged re-lengthening duration and intracellular Ca2+ derangement. These effects were significantly attenuated or absent in the TLR4 knockout mice. In addition, lethal toxin elicited autophagy in the absence of change in ER stress. Knockdown of TLR4 or class III PI3 kinase using siRNA but not the autophagy inhibitor 3-methyladenine significantly attenuated or inhibited lethal toxin-induced autophagy in H9C2 cells.

CONCLUSION AND IMPLICATIONS Our results suggest that TLR4 may be pivotal in mediating the lethal cardiac toxicity induced by anthrax possibly through induction of autophagy. These findings suggest that compounds that negatively modulate TLR4 signalling and autophagy could be used to treat anthrax infection-induced cardiovascular complications.