雌ニホンウズラの肝臓に及ぼす鉛の慢性曝露の影響：病理組織学的損傷、酸化ストレス、AMP活性化プロテインキナーゼに基づく脂質代謝障害

The effects of chronic lead exposure on the liver of female Japanese quail (Coturnix japonica): Histopathological damages, oxidative stress and AMP-activated protein kinase based lipid metabolism disorder.

• Honghong Kou
• Jing Ya
• Xuebin Gao
• Hongfeng Zhao

抄録

鉛（Pb）は、人間や野生生物にとって最も有害な金属の一つである。また、身体的、神経学的、血液学的な臨床徴候を持つ鳥類にも複数の悪影響を及ぼしていた。しかし、鳥類の肝臓脂質代謝に及ぼす鉛の影響はまだ明らかにされていない。本研究では、雌のニホンウズラを用いて、慢性的な鉛曝露が肝臓組織学、酸化ストレス、AMPK（AMP-activated protein kinase）に基づく脂質代謝に及ぼす影響を調べた。ウズラを5群に無作為に分け、各群に0, 50, 250, 500, 1000ppmの鉛水溶液を49日間与えた。その結果、250,500,1000ppm の鉛溶液に曝露した場合、肝脂質の液胞と蓄積、肝細胞のヒアリン化と液胞化、肝細胞の壊死、肝静脈洞のうっ血などの病理組織学的な損傷を引き起こし、さらにミトコンドリアの腫脹と液胞性ミトコンドリア、ポリリボソームの脱重合、脂質の液滴の蓄積などの超微細構造変化を引き起こした。さらに、すべての Pb 群の肝臓で、GPx（グルタチオンペルオキシダーゼ）、SOD（スーパーオキシドジスムターゼ）、CAT（カタラーゼ）、T-AOC（総抗酸化能）の活性が有意に低下する一方で、MDA（マロンジアルデヒド）含量が有意に増加していた。また、脂肪合成に関連する遺伝子の発現はすべてのPb群で有意に上昇したが、250ppmPb群では脂肪β酸化に関連する遺伝子の発現が有意に低下した。本研究では、鉛曝露が肝臓の微細構造や超微細構造の損傷、酸化的損傷、脂質代謝障害を誘発し、鳥類の健康被害を引き起こすことが示された。

Lead (Pb) is one of the most toxic metals to human and wildlife. It also had multiple negative influences on birds with physical, neurological and hematological clinical signs. However, the impacts of lead on bird liver lipid metabolism are still unclear. In this study, female Japanese quails were used to examine the effects of chronic lead exposure on liver histology, oxidative stress and AMPK (AMP-activated protein kinase) based lipid metabolism. Quails were randomly divided into 5 groups and each group was respectively fed with 0, 50, 250, 500 and 1000 ppm lead solution for 49 days. The result showed that exposure to 250, 500 and 1000 ppm Pb induced severe histopathological damages characterized by liver lipid vacuoles and accumulation, hepatic cytoplasmic hyalinization and vacuolization, hepatocytes necrosis, hepatic sinusoid congestion, and it also caused ultrastructural alterations featured by swelling and vacuolar mitochondria, the depolymerization of polyribosome, and lipid droplets accumulation. Moreover, significant decrease of activities of GPx (glutathione peroxidase), SOD (superoxide dismutase), CAT (catalase) and level of T-AOC (total antioxidant capacity) while significant increase of MDA (malondialdehyde) content were found in livers of all Pb groups. In addition, the expressions of genes related to fatty synthesis were significantly upregulated in livers of all Pb groups while the expressions of genes related to fatty β-oxidation were significantly downregulated in livers of 250 ppm Pb group. The present study indicated lead exposure does cause bird health damages through inducing liver microstructural and ultrastructural injury, oxidative damages and lipid metabolism disorder.

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