Docosahexaenoic Acid Alleviates Trimethylamine-N-oxide-mediated Impairment of Neovascularization in Human Endothelial Progenitor Cells.

BACKGROUND: Human endothelial progenitor cells (hEPCs), originating from hemangioblasts in bone marrow (BM), migrate into the blood circulation, differentiate into endothelial cells, and could act as an alternative tool for tissue regeneration. In addition, trimethylamine-N-oxide (TMAO), one of the gut microbiota metabolites, has been identified as an atherosclerosis risk factor. However, the deleterious effects of TMAO on the neovascularization of hEPCs have not been studied yet. RESULTS: Our results demonstrated that TMAO dose-dependently impaired human stem cell factor (SCF)-mediated neovascularization in hEPCs. The action of TMAO was through the inactivation of Akt/endothelial nitric oxide synthase (eNOS), MAPK/ERK signaling pathways, and an upregulation of microRNA (miR)-221. Docosahexaenoic acid (DHA) could effectively inhibit the cellular miR-221 level and induce the phosphorylation level of Akt/eNOS, MAPK/ERK signaling molecules, and neovascularization in hEPCs. DHA enhanced cellular amounts of reduced form glutathione (GSH) through an increased expression of the gamma-glutamylcysteine synthetase (γ-GCS) protein. CONCLUSIONS: TMAO could significantly inhibit SCF-mediated neovascularization, in part in association with an upregulation of miR-221 level, inactivation of Akt/eNOS and MAPK/ERK cascades, suppression of γ-GCS protein, and decreased levels of GSH and GSH/GSSG ratio. Furthermore, the DHA could alleviate the detrimental effects of TMAO and induce neovasculogenesis through suppression of miR-221 level, activation of Akt/eNOS and MAPK/ERK signaling cascades, increased expression of γ-GCS protein, and increment of cellular GSH level and GSH/GSSG ratio in hEPCs.

Neovasculogenic effect of 11,12-epoxyeicosatrienoic acid involves the Akt/eNOS signaling pathways in human endothelial progenitor cells.

The 11,12-epoxy-eicosatrienoic acid (11,12-EET) is formed from arachidonic acid (AA) by cytochrome P450 2J2 (CYP 2J2) epoxygenase and function as an effector in blood vessels. Human endothelial progenitor cells (hEPCs), a preceding cell source for endothelial cells (ECs), involve in the vascular tissue repairing by postnatal neovasculogenesis. However, the effect of 11, 12-EET on hEPCs and neovasculogenesis is not well known. In the current study, we examined the function of 11, 12-EET in hEPCs-mediated neovasculogenesis by using tubular formation analysis, Western Blotting assay, immunofluorescence staining, flow cytometry analysis and zymogram analysis. The results suggest that 11, 12-EET significantly induces neovasculogenesis through the phosphorylation of phosphoinositide 3-kinase (PI3-K)/Akt, endothelial-nitric oxide synthase (e-NOS) and extracellular signal-regulated kinase 1/2 (ERK 1/2) signaling pathways. 11, 12-EET up-regulates the expression of cyclin D1, cyclin-dependent kinase 4 (CDK4) and nuclear factor kappa B (NF-κB) proteins. Moreover, 11, 12-EET augments the expression of VE-cadherin and CD31 proteins in hEPCs. 11, 12-EET also augmented Rac1/Rho A signaling cascades, cell migration and an up-regulation of matrix metalloproteinase (MMP) -2 and -9 proteins. These results demonstrate that 11, 12-EET exerts a significant function in the neovasculogenesis of hEPCs.

N-3 polyunsaturated fatty acids block the trimethylamine-N-oxide- ACE2- TMPRSS2 cascade to inhibit the infection of human endothelial progenitor cells by SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) is a novel coronavirus that infects many types of cells and causes cytokine storms, excessive inflammation, acute respiratory distress to induce failure of respiratory system and other critical organs. In this study, our results showed that trimethylamine-N-oxide (TMAO), a metabolite generated by gut microbiota, acts as a regulatory mediator to enhance the inerleukin-6 (IL-6) cytokine production and the infection of human endothelial progenitor cells (hEPCs) by SARS-CoV-2. Treatment of N-3 polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) could effectively block the entry of SARS-CoV-2 in hEPCs. The anti-infection effects of N-3 PUFAs were associated with the inactivation of NF-κB signaling pathway, a decreased expression of the entry receptor angiotensin-converting enzyme 2 (ACE2) and downstream transmembrane serine protease 2 in hEPCs upon the stimulation of TMAO. Treatment of DHA and EPA further effectively inhibited TMAO-mediated expression of IL-6 protein, probably through an inactivation of MAPK/p38/JNK signaling cascades and a downregulation of microRNA (miR)-221 in hEPCs. In conclusion, N-3 PUFAs such as DHA and EPA could effectively act as preventive agents to block the infection of SARS-CoV-2 and IL-6 cytokine production in hEPCs upon the stimulation of TMAO.

Docosahexaenoic Acid Inhibits Cell Proliferation through a Suppression of c-Myc Protein in Pancreatic Ductal Adenocarcinoma Cells.

Treatment of pancreatic cancer by inhibiting the aberrant activation of the survival signaling pathways has received considerable attention. We investigated the probable action of DHA on the suppression of cell proliferation in human pancreatic ductal adenocarcinoma (PDAC) cells. Our results demonstrated that DHA dose-dependently inhibited cell proliferation through an induction of cell cycle arrest in human PDAC cells. DHA suppressed the expression of phosphorylated-Rb (p-Rb), cyclin D1, cyclin E, cyclin A, E2F1 and c-Myc proteins. Blocking the activation of STAT3 signaling pathway led to an inactivation of CAMKII and increased phosphorylation of c-Myc (T58) protein accompanied with decreased expression of c-Myc protein. Treatment of DHA effectively inhibited cell survival through decreased phosphorylation levels of EGFR, STAT3 and CAMKII proteins. The mechanisms of action were associated with increased phosphorylation levels of c-Myc (T58) and instability of c-Myc proteins. DHA inhibited cell survival through an increased GSSG/GSH ratio and oxidative stress level in HPAF-II cells. DHA induced cell apoptosis through increased expression of Bax, c-caspase 3 and c-PARP proteins in HPAF-II cells. Moreover, treatment of DHA significantly inhibited nucleotide synthesis. In conclusion, DHA might significantly suppress the proliferation of PDAC cells and therefore have potential as an anti-cancer therapeutic agent.

Treatment of 13-cis retinoic acid and 1,25-dihydroxyvitamin D3 inhibits TNF-alpha-mediated expression of MMP-9 protein and cell invasion through the suppression of JNK pathway and microRNA 221 in human pancreatic adenocarcinoma cancer cells.

Human pancreatic ductal adenocarcinoma (PDAC) is a deadly cancer type with a very high mortality rate. Inflammatory cytokine such as tumor necrosis factor- alpha (TNF-α) plays a pivotal role in the progression of PDAC. Recently, suppression of cell invasion by preventive agents has received considerable attention in the prevention of metastatic tumors. Several clinical studies suggested that natural forms or analogues of fat-soluble vitamins such as vitamin A and vitamin D can work as anti-cancer agents to inhibit the development of cancer. In this study, our results demonstrated that co-treatment of 13-cis retinoic acid (13-cis RA) and 1,25-dihydroxyvitamin D3 (1,25-VD3) significantly inhibited TNF-α mediated cell invasion in PDAC in vitro. Cotreatment of 13-cis RA and 1,25-VD3 also inhibited TNF-α mediated expression of matrix metalloproteinase-9 (MMP-9) protein through blocking c-Jun N-terminal kinase (JNK) and nuclear factor kappa B (NF-κB) signaling pathways. Our results demonstrated that treatment of TNF-α lead to a decreased expression of tissue inhibitor of metalloproteinase- 3 (TIMP-3) protein and an induction of MMP-9 protein and cell invasion through an upregulation of microRNA-221 (miR-221) in human PDAC cells. Moreover, treatment of SP600125 (a specific inhibitor of JNK pathway) or cotreatment of 13-cis RA and 1,25-VD3 significantly induced a decreased expression of miR-221 and an increased expression of TIMP-3 protein. These results suggest that 13-cis RA and 1,25-VD3 significantly suppress TNF-α mediated cell invasion and therefore potentially act as preventive agents against PDAC.

Docosahexaenoic acid inhibits the proliferation of Kras/TP53 double mutant pancreatic ductal adenocarcinoma cells through modulation of glutathione level and suppression of nucleotide synthesis.

The treatment of cancer cells obtained by blocking cellular metabolism has received a lot of attention recently. Previous studies have demonstrated that Kras mutation-mediated abnormal glucose metabolism would lead to an aberrant cell proliferation in human pancreatic ductal adenocarcinoma (PDAC) cells. Previous literature has suggested that consumption of fish oil is associated with lower risk of pancreatic cancer. In this study, we investigated the anti-cancer effects of docosahexaenoic acid (DHA) in human PDAC cells in vitro and in vivo. Omega-3 polyunsaturated fatty acids (PUFAs) such as DHA and eicosapentaenoic acid (EPA) significantly inhibited the proliferation of human PDAC cells. The actions of DHA were evaluated through an induction of cell cycle arrest at G1 phase and noticed a decreased expression of cyclin A, cyclin E and cyclin B proteins in HPAF-II cells. Moreover, it was found that co-treatment of DHA and gemcitabine (GEM) effectively induced oxidative stress and cell death in HPAF-II cells. Interestingly, DHA leads to an increased oxidative glutathione /reduced glutathione (GSSG/GSH) ratio and induced cell apoptosis in HPAF-II cells. The findings in the study showed that supplementation of GSH or N-Acetyl Cysteine (NAC) could reverse DHA-mediated cell death in HPAF-II cells. Additionally, DHA significantly increased cellular level of cysteine, cellular NADP/NADPH ratio and the expression of cystathionase (CTH) and SLCA11/xCT antiporter proteins in HPAF-II cells. The action of DHA was, in part, associated with the inactivation of STAT3 cascade in HPAF-II cells. Treatment with xCT inhibitors, such as erastin or sulfasalazine (SSZ), inhibited the cell survival ability in DHA-treated HPAF-II cells. DHA also inhibited nucleotide synthesis in HPAF-II cells. It was demonstrated in a mouse-xenograft model that consumption of fish oil significantly inhibited the growth of pancreatic adenocarcinoma and decreased cellular nucleotide level in tumor tissues. Furthermore, fish oil consumption induced an increment of GSSG/GSH ratio, an upregulation of xCT and CTH proteins in tumor tissues. In conclusion, DHA significantly inhibited survival of PDAC cells both in vitro and in vivo through its recently identified novel mode of action, including an increment in the ratio of GSSG/GSH and NADP/NADPH respectively, and promoting reduction in the levels of nucleotide synthesis.

S-allylcysteine Improves Blood Flow Recovery and Prevents Ischemic Injury by Augmenting Neovasculogenesis.

Studies suggest that a low level of circulating human endothelial progenitor cells (EPCs) is a risk factor for ischemic injury and coronary artery disease (CAD). Consumption of S-allylcysteine (SAC) is known to prevent CAD. However, the protective effects of SAC on the ischemic injury are not yet clear. In this study, we examined whether SAC could improve blood flow recovery in ischemic tissues through EPC-mediated neovasculogenesis. The results demonstrate that SAC significantly enhances the neovasculogenesis of EPCs in vitro. The molecular mechanisms for SAC enhancement of neovasculogenesis include the activation of Akt/endothelial nitric oxide synthase signaling cascades. SAC increased the expression of c-kit, ß-catenin, cyclin D1, and Cyclin-dependent kinase 4 (CDK4) proteins in EPCs. Daily intake of SAC at dosages of 0.2 and 2 mg/kg body weight significantly enhanced c-kit protein levels in vivo. We conclude that dietary consumption of SAC improves blood flow recovery and prevents ischemic injury by inducing neovasculogenesis in experimental models.

N-3 polyunsaturated fatty acids alleviate high glucose-mediated dysfunction of endothelial progenitor cells and prevent ischemic injuries both in vitro and in vivo.

Hyperglycemia is associated with a reduced number of endothelial progenitor cells (EPCs) that impairs vascular function. Circulating EPCs play important roles in postnatal neovasculogenesis and the prevention of ischemic injury. Frequent consumption of fish oil (FO) that is abundant with eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) is reportedly associated with an alleviation of diabetic complications and a lowered incidence of cardiovascular disease. The aim of this study was to examine whether N-3 polyunsaturated fatty acids such as EPA and DHA would reverse the high glucose-mediated dysfunction of EPCs in vitro and thereby prevent the ischemic injury that occurs under the hyperglycemic conditions in Type 2 diabetes (T2D) db-/- mice. The results demonstrate that EPA and DHA alleviate high glucose-mediated impairment of tubular formation in EPCs through a rescue of neovasculogenic capability. The molecular mechanisms underlying the effects of EPA and DHA include the activation of the extracellular signal-regulated kinase 1/2, Akt/endothelial nitric oxide synthase (eNOS) and AMP-activated kinase (AMPK) signaling cascades as well as the phosphorylation of the downstream FOXO3a protein in EPCs. Moreover, EPA and DHA up-regulate the expression of c-kit, erythroid 2-related factor and heme oxygenase-1 proteins. Daily consumption of FO at dosages of 4% and 6% (wt/wt) significantly increased the level of bone marrow-derived and circulating EPCs, induced a recovery of blood flow and prevented ischemic injuries in a T2D db-/- mouse model. The effects of FO consumption were exerted the activation of Akt/eNOS and AMPK signaling cascades without any effect on the plasma VEGF level in vivo.

Eicosapentaenoic acid induces neovasculogenesis in human endothelial progenitor cells by modulating c-kit protein and PI3-K/Akt/eNOS signaling pathways.

Human endothelial progenitor cells (hEPCs) derived from bone marrow play a crucial in the prevention of ischemic injuries in the course of postnatal neovasculogenesis. Frequent fish oil (FO) consumption is reportedly associated with a significantly lower incidence of cardiovascular disease. However, the molecular mechanisms of eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) are not well elucidated, and the beneficial effect of FO consumption on neovasculogenesis has not been demonstrated yet. In the current study, we investigated the effects of EPA/DHA and FO consumption on neovasculogenesis by using vascular tube formation assay, Western blotting, real-time polymerase chain reaction, immunohistochemical staining and Doppler imaging in both in vitro and in vivo models. The results demonstrate that EPA and DHA dose-dependently enhance the neovasculogenesis and cell migration of hEPCs in vitro. The mechanisms of action included up-regulation of the c-kit protein as well as the phosphorylation of the ERK1/2, Akt and endothelial nitric oxide synthase signaling molecules in hEPCs. Furthermore, EPA significantly suppressed the expression of microRNA 221 in vitro. In experimental animal models, FO consumption significantly induced the formation of new blood vessels (neovasculogenesis) and prevented ischemia. Taken together, it is suggested that FO consumption enhances neovasculogenesis mainly through the effects of EPA in hEPCs, thereby exerting a preventive effect against ischemic injury.