Dihydroartemisinin inhibits colon cancer cell viability by inducing apoptosis through up-regulation of PPARγ expression

The present study was aimed to investigate the effect of dihydroartemisinin on the colon cancer cell proliferation and apoptosis. The results from MTT assay revealed a concentration and time dependent relation between the inhibition of SW 948 cell viability and dihydroartemisinin addition. The viability of SW 948 cells was reduced to 45 and 24% on treatment with 30 and 50 µM, respectively concentrations of dihydroartemisinin after 48 h. Morphological examination of SW 948 cells showed attainment of rounded shape and cluster formation on treatment with dihydroartemisinin. Western blot analysis showed a significant increase in the activation of caspase-3 and expression of cleaved PARP by dihydroartemisinin treatment. The activation of PPARγ was increased significantly in SW 948 cells by treatment with dihydroartemisinin. Compared to control, the migration potential of SW 948 cells was reduced significantly (p < 0.005) and the expression levels of MMP-2 and -9 inhibited by dihydroartemisinin at 50 µM concentration. In the dihydroartemisinin treatment group colon tumor formation was significantly inhibited on treatment with 20 mg/kg doses of dihydroartemisinin after 30 days. Therefore, dihydroartemisinin inhibits colon cancer growth by inducing apoptosis and increasing the expression of PPARγ. Thus dihydroartemisinin can be used for the treatment of colon cancer.     

Prostaglandin reductase-3 negatively modulates adipogenesis through regulation of PPARγ activity

Adipocyte differentiation is a multistep program under regulation by several factors. Peroxisome proliferator-activated receptor γ (PPARγ) serves as a master regulator of adipogenesis. However, the endogenous ligand for PPARγ remained elusive until 15-keto-PGE₂ was identified recently as an endogenous PPARγ ligand. In this study, we demonstrate that zinc-containing alcohol dehydrogenase 2 (ZADH2; here termed prostaglandin reductase-3, PTGR-3) is a new member of prostaglandin reductase family that converts 15-keto-PGE₂ to 13,14-dihydro-15-keto-PGE₂. Adipogenesis is accelerated when endogenous PTGR-3 is silenced in 3T3-L1 preadipocytes, whereas forced expression of PTGR-3 significantly decreases adipogenesis. PTGR-3 expression decreased during adipocyte differentiation, accompanied by an increased level of 15-keto-PGE₂. 15-keto-PGE₂ exerts a potent proadipogenic effect by enhancing PPARγ activity, whereas overexpression of PTGR-3 in 3T3-L1 preadipocytes markedly suppressed the proadipogenic effect of 15-keto-PGE₂ by repressing PPARγ activity. Taken together, these findings demonstrate for the first time that PTGR-3 is a novel 15-oxoprostaglandin-Δ¹³-reductase and plays a critical role in modulation of normal adipocyte differentiation via regulation of PPARγ activity. Thus, modulation of PTGR-3 might provide a novel avenue for treating obesity and related metabolic disorders.     

Cardioprotection from oxidative stress in the newborn heart by activation of PPARγ is mediated by catalase

Regulation of catalase (CAT) by peroxisome proliferator-activated receptor-γ (PPARγ) was investigated to determine if PPARγ activation provides cardioprotection from oxidative stress caused by hydrogen peroxide (H(2)O(2)) in an age-dependent manner. Left ventricular developed pressure (LVDP) was measured in Langendorff perfused newborn or adult rabbit hearts, exposed to 200μM H(2)O(2), with perfusion of rosiglitazone (RGZ) or pioglitazone (PGZ), PPARγ agonists. We found: (1) H(2)O(2) significantly decreased sarcomere shortening in newborn ventricular cells but not in adult cells. Lactate dehydrogenase (LDH) release occurred earlier in newborn than in adult heart, which may be due, in part, to the lower expression of CAT in newborn heart. (2) RGZ increased CAT mRNA and protein as well as activity in newborn but not in adult heart. GW9662 (PPARγ blocker) eliminated the increased CAT mRNA by RGZ. (3) In newborn heart, RGZ and PGZ treatment inhibited release of LDH in response to H(2)O(2) compared to H(2)O(2) alone. GW9662 decreased this inhibition. (4) LVDP was significantly higher in both RGZ+H(2)O(2) and PGZ+H(2)O(2) groups than in the H(2)O(2) group. Block of PPARγ abolished this effect. In contrast, there was no effect of RGZ in adult. (5) The cardioprotective effects of RGZ were abolished by inhibition of CAT. In conclusion, PPARγ activation is cardioprotective to H(2)O(2)-induced stress in the newborn heart by upregulation of catalase. These data suggest that PPARγ activation may be an effective therapy for the young cardiac patient.     

MicroRNA-302a inhibits adipogenesis by suppressing peroxisome proliferator-activated receptor γ expression

The present study explored the involvement of miR-302a in adipocyte differentiation via interaction with 3′-untranslated region of peroxisome proliferator-activated receptor gamma (PPARγ) mRNA. In differentiating 3T3-L1 adipocytes, expression of miR-302a was negatively correlated with that of the adipogenic gene aP2 and PPARγ. Overexpression of miR-302a inhibited adipogenic differentiation with lipid accumulation, and inversely anti-miR-302a increased the differentiation. In silico analysis revealed a complementary region of miR-302a seed sequence in 3′-UTR of PPARγ mRNA. Luciferase assay showed the direct interaction of miR-302a with PPARγ at the cellular level. The miR-302a inhibition of adipocyte differentiation was reversed by PPARγ overexpression. These findings suggest that miR-302a might be a negative regulator of adipocyte differentiation and that the dysregulation of miR-302a should lead to metabolic disorders.     

Deciphering PPARγ activation in cardiometabolic syndrome: studies by in silico and in vivo experimental assessment

Cardiometabolic syndrome (CMetS) is a consolidation of metabolic disorders characterized by insulin resistance, dyslipidemia and hypertension. Curcumin, a natural bioactive compound, has been shown to possess notable anti-oxidant activity and it has also been included as a super natural herb in the super natural herbs database. Most of the beneficial effects of Curcumin are possibly due to activation of the nuclear receptor, peroxisome proliferator-activated receptor gamma (PPARγ). The present study investigates molecular interactions of curcumin with PPARγ protein through molecular docking and molecular dynamics (MD) simulation studies. Further, effect of curcumin on high fat diet induced CMetS was studied in rats along with western blot for PPARγ and nuclear factor-κB (NF-κB) expressions and histopathological studies. Computational studies presented several significant molecular interactions of curcumin including Ser289, His323, His449 and Tyr473 of PPARγ. The in vivo results further confirmed that curcumin was able to ameliorate the abnormal changes and also, increased PPARγ expressions. The results confirm our hypothesis that activation of PPARγ by curcumin possesses the therapeutic potential to ameliorate the altered levels of metabolic changes in rats in the treatment of CMetS. This is the first report of CMetS treatment by curcumin and study of its underlying mechanism through in silico as well as in vivo experiments.     

Socs3 induction by PPARγ restrains cancer-promoting inflammation

Integrin-linked kinase (ILK) plays key roles in a variety of cell functions, including cell proliferation, adhesion and migration. Within the cell, ILK localizes to multiple sites, including the cytoplasm, focal adhesion complexes that mediate cell adhesion to extracellular substrates, as well as cell-cell junctions in epidermal keratinocytes. Central to understanding ILK function is the elucidation of the mechanisms that regulate its subcellular localization. We now demonstrate that ILK is imported into the nucleus through sequences in its N-terminus, via active transport mechanisms that involve nuclear pore complexes. In addition, nuclear ILK can be rapidly exported into the cytoplasm through a CRM1-dependent pathway, and its export is enhanced by the type 2C protein phosphatase ILKAP. Nuclear localization of ILK in epidermal keratinocytes is associated with increased DNA synthesis, which is sensitive to inhibition by ILKAP. Our studies demonstrate the importance for keratinocyte proliferation of ILK regulation through changes in its subcellular localization, and establish ILKAP and CRM1 as pivotal modulators of ILK subcellular distribution and activity in these cells.