Procyanidin B2

Chem Biol Interact. 2015 May 25;233:122-38.

Mechanisms of DNA methyltransferase-inhibitor interactions: Procyanidin B2 shows new promise for therapeutic intervention of cancer.[Pubmed: 25839702]

DNA methyltransferases (DNMTs) is a key epigenetic enzyme for pharmacological manipulation and is employed in cancer reprogramming. During past few years multiple strategies have been implemented to excavate epigenetic compounds targeting DNMTs.
METHODS AND RESULTS:
In light of the emerging concept of chemoinformatics, molecular docking and simulation studies have been employed to accelerate the development of DNMT inhibitors. Among the DNMT inhibitors known till date, epigallocathechin-3-gallate (EGCG) was identified to be effective in reducing DNMT activity. However, the broad spectrum of EGCG to other diseases and variable target enzymes offers some limitations. In view of this, 32 EGCG analogues were screened at S-Adnosyl-L-homocysteine (SAH) binding pocket of DNMTs and Procyanidin B2-3, 3'-di-O-gallate (Procyanidin B2) was obtained as potent inhibitor having medicinally relevant chemical space. Further, in vitro analysis demonstrates the efficiency of Procyanidin B2 in attenuating DNMT activity at IC50 of 6.88±0.647 μM and subsequently enhancing the expression of DNMT target genes, E-cadherin, Maspin and BRCA1.
CONCLUSIONS:
Moreover, the toxic property of Procyanidin B2 towards triple negative breast cancer cells to normal cells offers platform for pre-clinical trial and an insight to the treatment of cancer.

Mol Nutr Food Res. 2015 Feb;59(2):262-9.

Procyanidin B2 inhibits inflammasome-mediated IL-1β production in lipopolysaccharide-stimulated macrophages.[Pubmed: 25379992]

Macrophage stimulation with bacterial LPS triggers inflammasome activation, resulting in pro-inflammatory IL-1β cytokine maturation and secretion. IL-1β underlies the pathologies of many diseases, including type-2 diabetes. Thus, the modulation of the inflammatory response through bioactive food compounds, such as procyanidins, is a powerful tool to promote homeostasis.
METHODS AND RESULTS:
To determine the role of Procyanidin B2 in inflammasome activation, LPS-primed THP-1-macrophages were supplemented with or without Procyanidin B2 . Western blot analysis of COX2 , iNOS, p65, NLRP3 and IL-1β was performed followed by p65 supershift assay, in vivo caspase-1 activation assay and NO, IL-1β and IL-6 determination. Procyanidin B2 mediated inhibition of inflammasome activation includes the inactivation of the NF-κB signalling pathway, the first stage required for the transcription of inflammasome precursors, through the inhibition of p65 nuclear expression and DNA binding, resulting in the transcriptional repression of target genes, such as COX2 , iNOS and production of IL-6 and NO. Furthermore, Procyanidin B2 decreases NLRP3 and pro-IL-1β cytoplasmic pools, limiting components of inflammasome activation and impeding inflammasome assembly and caspase-1 activation, and finally secretion of active IL-1β.
CONCLUSIONS:
This study provides the first evidence that Procyanidin B2 inhibits inflammasome activation and IL-1β secretion during LPS-induced acute inflammation in human macrophages.

Free Radic Biol Med. 2005 Oct 15;39(8):1041-9.

Procyanidin B2 has anti- and pro-oxidant effects on metal-mediated DNA damage.[Pubmed: 16198231 ]

Procyanidin B2 (epicatechin-(4beta-8)-epicatechin), which is present in grape seeds, apples, and cacao beans, has antioxidant properties. We investigated the mechanism of preventive action of Procyanidin B2 against oxidative DNA damage in human cultured cells and isolated DNA.
METHODS AND RESULTS:
Procyanidin B2 inhibited the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in the human leukemia cell line HL-60 treated with an H2O2-generating system. In contrast, a high concentration of Procyanidin B2 increased the formation of 8-oxodG in HL-60 cells. Experiments with calf thymus DNA also revealed that Procyanidin B2 decreased 8-oxodG formation by Fe(II)/H2O2, whereas Procyanidin B2 induced DNA damage in the presence of Cu(II), and H2O2 extensively enhanced it. An electron spin resonance spin trapping study utilizing 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO) demonstrated that Procyanidin B2 decreased the signal of M4PO-OH from H2O2 and Fe(II), whereas Procyanidin B2 enhanced the signal from H2O2 and Cu(II). As an antioxidant mechanism, UV-visible spectroscopy showed that Procyanidin B2 chelated Fe(II) at equivalent concentrations. As a pro-oxidant property, we examined DNA damage induced by Procyanidin B2, using 32P-labeled DNA fragments obtained from genes relevant to human cancer.
CONCLUSIONS:
Our results raise the possibility that Procyanidin B2 exerts both antioxidant and pro-oxidant properties by interacting with H2O2 and metal ions.

Chem Biol Interact. 2014 Sep 6;222C:68-76.

Effect of cinnamon and its procyanidin-B2 enriched fraction on diabetic nephropathy in rats.[Pubmed: 25199697]

Non-enzymatic protein glycation and resultant accumulation of advanced glycation endproducts (AGE) are implicated in the pathogenesis of diabetic complications including diabetic nephropathy (DN). It is considered that antiglycating agents offer protection against AGE mediated pathologies including DN. Earlier we characterized procyanidin-B2 (PCB2) as the active component from cinnamon (Cinnamomum zeylanicum) that inhibits AGE formation in vitro.
METHODS AND RESULTS:
In this study, we have investigated the potential of PCB2-enriched fraction of cinnamon to prevent in vivo accumulation of AGE and to ameliorate renal changes in diabetic rats. Streptozotocin-induced diabetic rats were fed with either 3% cinnamon or 0.002% PCB2-fraction in diet for 12weeks. Biochemical analysis of blood and urine was performed at the end of experiment. Evaluation of glomerular markers that serve as indicators of renal function was done by immunohistochemistry, immunoblotting and qRT-PCR. Supplementation of diabetic rats with cinnamon and PCB2-fraction prevented glycation mediated RBC-IgG cross-links and HbA1c accumulation in diabetes rats. Cinnamon and PCB2-fraction also inhibited the accumulation of N-carboxy methyl lysine (CML), a prominent AGE in diabetic kidney. Interestingly, cinnamon and its PCB2-fraction prevented the AGE mediated loss of expression of glomerular podocyte proteins; nephrin and podocin. Inhibition of AGE by cinnamon and PCB2-fraction ameliorated the diabetes mediated renal malfunction in rats as evidenced by reduced urinary albumin and creatinine.
CONCLUSIONS:
In conclusion, PCB2 from cinnamon inhibited AGE accumulation in diabetic rat kidney and ameliorated AGE mediated pathogenesis of DN.

Biochem Pharmacol. 2014 Dec 15;92(4):599-606.

Procyanidin B2 inhibits NLRP3 inflammasome activation in human vascular endothelial cells.[Pubmed: 25450671]

Procyanidins are the flavanols from polyphenols commonly found in fruits and red wine. Recent studies have shown that procyanidins possess potential anti-inflammatory activities. However, underlying mechanisms remain to be understood. Inflammasomes are multi-protein complexes composed of pro-caspase and pattern recognition receptors (PRRs) such as NOD-like receptor family, pyrin domain containing 3 (NLRP3).
METHODS AND RESULTS:
Since aberrant activation of NLRP3 inflammasome is implicated in the pathogeneses of pro-inflammatory diseases such as diabetes, atherosclerosis and arthritis, we aimed to investigate whether Procyanidin B2 (PCB2), the most widely distributed natural procyanidins, inhibits the activation of NLRP3 inflammasome in endothelial cells (ECs). We found that, in human umbilical vein ECs (HUVECs), PCB2 significantly suppressed the activation of NLRP3 inflammasome and inhibited subsequent caspase-1 activation and interleukin (IL)-1β secretion in response to lipopolysaccharides (LPS). PCB2 negatively regulated the gene expression of NLRP3. In addition, PCB2 attenuated LPS-induced production of reactive oxygen species (ROS) and the transcriptional activity of activator protein-1 (AP-1). In conclusion, we demonstrated for the first time that Procyanidin B2 inhibits NLRP3 inflammasome activation via suppression of AP-1 pathway in ECs.
CONCLUSIONS:
These results suggest a new mechanism by which natural flavoids such as procyanidins exert their vascular protective effects.

Eur J Nutr. 2012 Oct;51(7):881-92.

Procyanidin B2 induces Nrf2 translocation and glutathione S-transferase P1 expression via ERKs and p38-MAPK pathways and protect human colonic cells against oxidative stress.[Pubmed: 22042007 ]

Procyanidin B2 (PB2) is a naturally occurring flavonoid widely found in cocoa, red wine and grape juice. Recent studies have suggested that PB2 could protect against oxidative stress- and chemical-induced injury in colonic cells by modulating the endogenous cellular defence. However, the precise mechanism for this protection is not fully understood. Herein, we examined the effect of PB2 on the expression of one of the major antioxidant/detoxificant enzymes related to intestinal protection, the glutathione S-transferase P1 (GSTP1), and the molecular mechanisms involved.
METHODS AND RESULTS:
Human colonic Caco-2 cells were treated with PB2 at different times and enzymatic activity, and mRNA and protein levels of GSTP1 were evaluated. The nuclear translocation of the transcription factor NF-erythroid 2-related factor (Nrf2) and the phosphorylation states of specific proteins central to intracellular signalling cascades were also investigated. PB2 induced the expression and activity of GSTP1 and the nuclear translocation of Nrf2. Interestingly, two important signalling proteins involved in Nrf2 translocation, the extracellular signal-regulated protein kinases (ERKs) and the p38 mitogen-activated protein kinase (MAPK) were also activated. Further experiments with specific inhibitors of both pathways confirmed their critical role in the beneficial effects induced by PB2.
CONCLUSIONS:
The present results show that PB2 protects against oxidative injury in colonic cells and up-regulate the expression of GSTP1 via a mechanism that involves ERK and p38 MAPK activation and Nrf2 translocation. These results provide a molecular basis for the potential contribution of PB2 in the prevention of oxidative stress-related intestinal injury and gut pathologies.