Pterostilbene, a natural analogue of resveratrol, potently inhibits 7,12-dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse skin carcinogenesis.

We reported previously that pterostilbene, a natural analogue of resveratrol from blueberries, strongly suppressed lipopolysaccharide-induced up-expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in murine macrophages. In this study, we further investigated pterostilbene's molecular mechanism of action and its anti-tumor properties. Pretreatment with pterostilbene has resulted in the reduction of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced nuclear translocation of the nuclear factor-κB (NFκB) subunits. Pterostilbene also reduced TPA-induced phosphorylation of IκBα and p65 and caused subsequent degradation of IκBα. Moreover, pterostilbene markedly suppressed TPA-induced activation of extracellular signal-regulated kinase (ERK)1/2, p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK)1/2, phosphatidylinositol 3-kinase (PI3K) and Akt, which are upstream of NFκB and activator protein 1 (AP-1). Furthermore, pterostilbene significantly inhibited 7,12-dimethylbenz[a]anthracene (DMBA)/TPA-induced skin tumor formation measured by the tumor multiplicity of papillomas at 20 weeks. The presented data has, for the first time, revealed that pterostilbene is an effective anti-tumor agent that functions by downregulating inflammatory iNOS and COX-2 gene expression in mouse skin. It is suggested that pterostilbene is a novel functional agent capable of preventing inflammation-associated tumorigenesis.

Pterostilbene suppressed lipopolysaccharide-induced up-expression of iNOS and COX-2 in murine macrophages.

Pterostilbene, an active constituent of blueberries, is known to possess anti-inflammatory activity and also to induce apoptosis in various types of cancer cells. Here, we investigated the inhibitory effects of pterostilbene on the induction of NO synthase (NOS) and cyclooxygenase-2 (COX-2) in murine RAW 264.7 cells activated with lipopolysaccharide (LPS). Western blotting and real-time polymerase chain reaction (PCR) analyses demonstrated that pterostilbene significantly blocked the protein and mRNA expression of iNOS and COX-2 in LPS-induced macrophages. Treatment with pterostilbene resulted in the reduction of LPS-induced nuclear translocation of the nuclear factor-kappaB (NFkappaB) subunit and the dependent transcriptional activity of NFkappaB by blocking phosphorylation of inhibitor kappaB (IkappaB)alpha and p65 and subsequent degradation of IkappaB alpha. Transient transfection experiments using NFkappaB reporter constructs indicated that pterostilbene inhibits the transcriptional activity of NFkappaB in LPS-stimulated mouse macrophages. We found that pterostilbene also inhibited LPS-induced activation of PI3K/Akt, extracellular signal-regulated kinase 1/2 and p38 MAPK. Taken together, these results show that pterostilbene down regulates inflammatory iNOS and COX-2 gene expression in macrophages by inhibiting the activation of NFkappaB by interfering with the activation of PI3K/Akt/IKK and MAPK. These results have an important implication for using pterostilbene toward the development of an effective anti-inflammatory agent.

Pterostilbene induces apoptosis and cell cycle arrest in human gastric carcinoma cells.

Pterostilbene, an active constituent of blueberries, is known to possess anti-inflammatory activity and also induces apoptosis in various types of cancer cells. Here, the effects of pterostilbene on cell viability in human gastric carcinoma AGS cells were investigated. This study demonstrated that pterostilbene was able to inhibit cell proliferation and induce apoptosis in a concentration- and time-dependent manner. Pterostilbene-induced cell death was characterized with changes in nuclear morphology, DNA fragmentation, and cell morphology. The molecular mechanism of pterostilbene-induced apoptosis was also investigated. The results show the caspase-2, -3, -8, and -9 are all activated by pterostilbene, together with cleavage of the downstream caspase-3 target DNA fragmentation factor (DFF-45) and poly(ADP-riobse) polymerase. Moreover, the results indicate that the Bcl-family of proteins, the mitochondrial pathway, and activation of the caspase cascade are responsible for pterostilbene-induced apoptosis. Pterostilbene markedly enhanced the expression of growth arrest DNA damage-inducible gene 45 and 153 (GADD45 and GADD153) in a time-dependent manner. Flow cytometric analysis indicated that pterostilbene blocked cell cycle progression at G1 phase in a dose- and time-dependent manner. Pterostilbene increased the p53, p21, p27, and p16 proteins and decreased levels of cyclin A, cyclin E, cyclin-dependent kinase 2 (Cdk2), Cdk4, and Cdk6, but the expression of cyclin D1 was not affected. Over a 24 h exposure to pterostilbene, the degree of phosphorylation of Rb was decreased after 6 h. In summary, pterostilbene induced apoptosis in AGS cells through activating the caspase cascade via the mitochondrial and Fas/FasL pathway, GADD expression, and by modifying cell cycle progress and changes in several cycle-regulating proteins. The induction of apoptosis by pterostilbene may provide a pivotal mechanism of the antitumor effects and for treatment of human gastric cancer.