虚血心筋にユビキチン陽性の好酸性封入体を認めた急性心筋梗塞症の1例

A Case of Acute Myocardial Infarction with Ubiquitin-positive Eosinophilic Inclusion Bodies in Ischemic Cardiac Myocytes

要旨　ユビキチン(Ub)・プロテアソームシステムは蛋白分解系の調節だけでなく，生体恒常性維持に重要な役割を担っている．各種の疾患時にUb陽性細胞が出現するが，形態学的にUb陽性を呈する細胞は限られている．われわれは各種間質性肺炎における肺胞上皮細胞に生じた好酸性封入体(Mallory body)はUb陽性であることを明らかにし，細胞傷害性との関連を検討してきた．一方，虚血時における心筋細胞質にびまん性好酸性変化が生じるが，心筋細胞の確実な封入体形成の報告は少ない．今回，心筋梗塞巣と正常部の境界領域(jeopardized zone)の虚血心筋細胞質内に好酸性封入体形成を認めた症例を経験した．心筋虚血，封入体，Ub陽性と細胞傷害との関連を組織学的に検討し，虚血時の心筋にも肺や他臓器に出現したものと同様のUb陽性封入体が存在し，Ub機構との関連が示された．

　The Ubiquitin(Ub)-proteasome system has a key role in homeostasis through proteasome-proteolysis and its contribution to protein expression and production. Under a light microscope, Ub-positive cells appear only in several diseased cells. We have found pneumocytes that were Ub-positive in interstitial pneumonia in accordance with the severity of pneumocyte injury. While, eosinophilic cytoplasmic degeneration is known to be one of the acute ischemic features in cardiac myocytes, no reports have been published about eosinophilic inclusions in cardiac myocytes. We report here the case of a Japanese female who died of acute myocardial infarction and in whom eosinophilic inclusions were found in cardiac myocytes in the border area between infarction and non-infarction myocardium(jeopardized zone). We found that these inclusions were positive for Ub and analysed the relationship between cardiac ischemia and the inclusions, immunohistochemically. Finally, we suspected that cardiac myocytes with Ub-positive inclusions might appear in acute ischemia under some conditions through the Ub-proteasome system.