Bodles Angela M, Varma Vijayalakshmi, Yao-Borengasser Aiwei, Phanavanh Bounleut, Peterson Charlotte A, McGehee Robert E, Rasouli Neda, Wabitsch Martin, Kern Philip A
The Central Arkansas Veterans Healthcare System, and the Department of Medicine, Division of Endocrinology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
J Lipid Res. 2006 Sep;47(9):2080-8. doi: 10.1194/jlr.M600235-JLR200. Epub 2006 Jun 23.
Metabolic syndrome and type 2 diabetes mellitus are associated with an increased number of macrophage cells that infiltrate white adipose tissue (WAT). Previously, we demonstrated that the treatment of subjects with impaired glucose tolerance (IGT) with the peroxisome proliferator-activated receptor gamma (PPARgamma) agonist pioglitazone resulted in a decrease in macrophage number in adipose tissue. Here, adipose tissue samples from IGT subjects treated with pioglitazone were examined for apoptosis with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. TUNEL-positive cells were identified, and there was a significant 42% increase in TUNEL-positive cells following pioglitazone treatment. Overlay experiments with anti-CD68 antibody demonstrated that most of the TUNEL-positive cells were macrophages. To determine whether macrophage apoptosis was a direct or indirect effect of pioglitazone treatment, human THP1 cells were treated with pioglitazone in vitro, demonstrating increased TUNEL staining in a dose- and time-dependent manner. Furthermore, the appearance of the active proteolytic subunits of caspase-3 and caspase-9 were detected in cell lysate from THP1 cells and also increased in a dose- and time-dependent manner following pioglitazone treatment. Pretreatment with a PPARgamma inhibitor, GW9662, prevented pioglitazone induction of the apoptotic pathway in THP1 cells. Differentiated human adipocytes did not show any significant increase in apoptosis after treatment in vitro with piolgitazone. These findings indicate that PPARgamma has distinct functions in different cell types in WAT, such that pioglitazone reduces macrophage infiltration by inducing apoptotic cell death specifically in macrophages through PPARgamma activation.
代谢综合征和2型糖尿病与浸润白色脂肪组织（WAT）的巨噬细胞数量增加有关。此前，我们证明，用过氧化物酶体增殖物激活受体γ（PPARγ）激动剂吡格列酮治疗糖耐量受损（IGT）的受试者，可使脂肪组织中的巨噬细胞数量减少。在此，我们用末端脱氧核苷酸转移酶介导的dUTP生物素缺口末端标记（TUNEL）染色法，检测了接受吡格列酮治疗的IGT受试者的脂肪组织样本中的细胞凋亡情况。识别出TUNEL阳性细胞，吡格列酮治疗后TUNEL阳性细胞显著增加了42%。用抗CD68抗体进行的叠加实验表明，大多数TUNEL阳性细胞是巨噬细胞。为了确定巨噬细胞凋亡是吡格列酮治疗的直接还是间接作用，我们在体外用吡格列酮处理人THP1细胞，结果显示TUNEL染色呈剂量和时间依赖性增加。此外，在THP1细胞的细胞裂解物中检测到了半胱天冬酶-3和半胱天冬酶-9的活性蛋白水解亚基，吡格列酮处理后也呈剂量和时间依赖性增加。用PPARγ抑制剂GW9662预处理可阻止吡格列酮诱导THP1细胞的凋亡途径。体外用人脂肪细胞分化后用吡格列酮处理，未显示凋亡有任何显著增加。这些发现表明，PPARγ在WAT的不同细胞类型中具有不同功能，即吡格列酮通过激活PPARγ特异性诱导巨噬细胞凋亡，从而减少巨噬细胞浸润。
