乙型肝炎病毒核心蛋白触发人肝癌细胞异常卟啉代谢的机制

How Hepatitis B Virus Core Protein Triggers Abnormal Metabolism of Porphyrin in Human Liver Cancer Cells

乙型肝炎病毒(Hepatitis B virus,HBV)与卟啉代谢之间相互作用的机制尚不清楚。为了探究HBV核心蛋白对人肝癌细胞中异常卟啉代谢途径的影响,以及HBV感染与迟发性皮肤卟啉症(Porphyria cutanea tarda,PCT)之间的联系,本研究通过HPLC分析比较用5-氨基乙酰丙酸(卟啉前体)处理后细胞中卟啉的积累和排泄;实时荧光定量PCR分析HBV核心蛋白对血红素加氧酶和尿卟啉原脱羧酶的基因表达的影响;Western Blot分析HBV核心蛋白表达细胞中FLVCR1和ABCG2表达水平。选取达州市中心医院收治的原发性肝癌患者16例,受试者均需实施原发性肝癌切除术,术后采集其肝癌中心位置的肿瘤标本,另取正常肝脏组织标本,分析两种标本的细胞内卟啉和血红素。结果发现与对照组Hepswx细胞相比,表达HBV核心蛋白的Hep39和Hep39b两种细胞内原卟啉IX和血红素明显降低,粪卟啉Ⅲ显著升高,说明HBV核心蛋白可诱导异常的细胞内卟啉代谢,并过量排泄粪卟啉Ⅲ。本研究结果表明HBV核心蛋白可能通过卟啉转运蛋白影响卟啉代谢,并促进过量粪卟啉原Ⅲ和/或粪卟啉Ⅲ的输出。HBV核心蛋白的存在上调了血红素加氧酶和尿卟啉原脱羧酶的基因表达水平,且影响ABCG2和FLVCR1两种卟啉输出蛋白的表达。本研究发现解释了HBV感染个体对PCT发展的易感性,并且揭示HBV核心蛋白可触发人肝癌细胞中异常的卟啉代谢。

It was unclear for the interaction mechanism between hepatitis B virus(HBV) and porphyrin metabolism. To explore the effect of HBV core protein(HBV-CP) on abnormal porphyrin metabolism in human liver cancer cells and the relationship between HBV infection and porphyria cutanea tarda(PCT),the accumulation and excretion of porphyrin in cells treated with 5-aminoacetylpropanoic acid(porphyrin precursor)were compared by HPLC;the effects of HBV-CP on mRNA expression of uroporphyrinogen decarboxylase(UROD) and heme oxygenase-1(HO-1) were analyzed by real-time fluorescence quantitative polymerase chain reaction(PCR);the protein expression of feline leukemia virus subgroup C receptor 1(FLVCR1)and ATP binding cassette sub-family G member 2(Junior blood group)(ABCG2)in cells expressing HBV-CP were analyzed by Western Blot. Sixteen patients with primary liver cancer(PLC)admitted to Dazhou Central Hospital for PLC resection were selected. Postoperatively,tissue in the center of the PLC was collected(PLC group,n=16). Samples of normal liver tissue were taken from patients with traumatic liver injury who underwent partial hepatectomy(Normal group,n=16). Intracellular levels of porphyrins and hemoglobin were measured. Compared with the control group,cells expressing HBV-CP had a lower amount of intracellular porphyrin Ⅸ and heme,and a higher amount of excreted fecal porphyrin Ⅲ(the oxidized form of fecal porphyrin Ⅲ). HBV-CP induced abnormal intracellular metabolism of porphyrin and excessive excretion of fecal porphyrin Ⅲ. These observations suggested that HBV-CP affected porphyrin metabolism and promoted excess expression of fecal porphyria III and/or fecal porphyrin Ⅲ,possibly via porphyrin transporter proteins. The presence of HBV-CP up-regulated the mRNA expression of HO-1 and UROD and affected the expression of the porphyrin output proteins,including ABCG2 and FLVCR1. Our findings explained the susceptibility of HBV-infected individuals to PLC development and suggested that HBC-CP appeared to trigger abnormal metabolism of porphyrin in human liver cancer cells.