Metabolomics of human umbilical vein endothelial cell-based analysis of the relationship between hyperuricemia and dyslipidemia

BACKGROUND AND AIMS

Hyperuricemia frequently accompanies dyslipidemia, yet the precise mechanism remains elusive. Leveraging cellular metabolomics analyses, this research probes the potential mechanisms wherein hyperuricemia provokes endothelial cell abnormalities, inducing disordered bile metabolism and resultant lipid anomalies.

METHODS AND RESULTS

We aimed to identify the differential metabolite associated with lipid metabolism through adopting metabolomics approach, and thereafter adequately validating its protective function on HUVECs by using diverse assays to measure cellular viability, reactive oxygen species, migration potential, apoptosis and gene and protein levels of inflammatory factors. Taurochenodeoxycholic acid (TCDCA) (the differential metabolite of HUVECs) and the TCDCA-involved primary bile acid synthesis pathway were found to be negatively correlated with high UA levels based on the results of metabolomics analysis. It was noted that compared to the outcomes observed in UA-treated HUVECs, TCDCA could protect against UA-induced cellular damage and oxidative stress, increase proliferation as well as migration, and decreases apoptosis. In addition, it was observed that TCDCA might protect HUVECs by inhibiting UA-induced p38 mitogen-activated protein kinase/nuclear factor kappa-B p65 (p38MAPK/NF-κB p65) pathway gene and protein levels, as well as the levels of downstream inflammatory factors.

CONCLUSION

The pathogenesis of hyperuricemia accompanying dyslipidemia may involve high uric acid levels eliciting inflammatory reactions and cellular damage in human umbilical vein endothelial cells (HUVECs), mediated through the p38MAPK/NF-κB signaling pathway, subsequently impinging on cellular bile acid synthesis and reducing bile acid production.

Bile acids regulate SF-1 to alter cholesterol balance in adrenocortical cells via S1PR2

Glucocorticoid synthesis typically occurs in adrenal cortex and is influenced by cholesterol balance, since cholesterol is the sole precursor of steroids. Bile acids as the signaling molecules, have been shown to promote steroidogenesis in steroidogenic cells. However, whether bile acids directly regulate cholesterol balance remains elusive. In this study, we prepared cholestatic mouse models and cultured human adrenocortical cells (H295R) treated with taurochenodeoxycholic acid (TCDCA) to determine transcription levels of cholesterol metabolism associated genes and cholesterol concentrations in adrenocortical cells. Results showed that common bile duct ligation (CBDL) and chenodeoxycholic acid (CDCA) feeding elevated the mRNA levels of Abca1, Cyp51, Hmgcr, Srb1, and Mc2r in adrenals of mice. Meanwhile, the concentrations of total cholesterol and cholesteryl ester in adrenals of CBDL and CDCA-fed mice were dramatically lowered. The total and phosphorylation levels of HSL in adrenal glands of CBDL mice were also enhanced. Similarly, TCDCA treatment in H295R cells decreased intracellular concentrations of total cholesterol and cholesteryl ester and increased transcription levels of SRB1, MC2R, and HSL as well. Inhibition of bile acids' receptor sphingosine 1-phosphate receptor 2 (S1PR2), extracellular signal-regulated kinase (ERK) phosphorylation, and steroidogenic factor 1 (SF-1) respectively successfully abolished effect of TCDCA on H295R cells. SF-1s was found to be phosphorylated at Thr75 in TCDCA-treated H295R cells. While a mild increase of intracellular cAMP concentration was detected upon TCDCA treatment, inhibition of PKA activity with Rp-Isomer in H295R cells failed to decrease the expression of SF-1 and its target genes. Our findings suggest that conjugated bile acids affect cholesterol balance through regulation of SF-1 in adrenocortical cells so as to provide an adequate cholesterol supply for glucocorticoid synthesis, which improves and enriches our understanding of the mechanism whereby bile acids regulate cholesterol balance to affect adrenal function.

Taurochenodeoxycholic acid reduces astrocytic neuroinflammation and alleviates experimental autoimmune encephalomyelitis in mice

OBJECTIVE

Multiple sclerosis (MS) is an immune regulatory disease that affects the central nervous system (CNS). The main pathological features include demyelination and neurodegeneration, and the pathogenesis is associated with astrocytic neuroinflammation. Taurochenodeoxycholic acid (TCDCA) is one of the conjugated bile acids in animal bile, and it is not clear whether TCDCA could improve MS by inhibiting the activation of astrocytes. This study was aimed to evaluate the effects of TCDCA on experimental autoimmune encephalomyelitis (EAE)-a classical animal model of MS, and to probe its mechanism from the aspect of suppressing astrocytic neuroinflammation. It is expected to prompt the potential application of TCDCA for the treatment of MS.

RESULTS

TCDCA effectively alleviated the progression of EAE and improved the impaired neurobehavior in mice. It mitigated the hyperactivation of astrocytes and down-regulated the mRNA expression levels of inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX2), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 in the brain cortex. In the C6 astrocytic cell line induced by lipopolysaccharide (LPS), TCDCA treatment dose-dependently decreased the production of NO and the protein expression of iNOS and glial fibrillary acidic protein (GFAP). TCDCA consistently inhibited the mRNA expressions of COX2, iNOS and other inflammatory mediators. Furthermore, TCDCA decreased the protein expression of phosphorylated serine/threonine kinase (AKT), inhibitor of NFκB α (IκBα) and nuclear factor κB (NFκB). And TCDCA also inhibited the nuclear translocation of NFκB. Conversely, as an inhibitor of the G-protein coupled bile acid receptor Gpbar1 (TGR5), triamterene eliminated the effects of TCDCA in LPS-stimulated C6 cells.

CONCLUSION

TCDCA improves the progress of EAE by inhibiting the astrocytic neuroinflammation, which might be exerted by the regulation of TGR5 mediated AKT/NFκB signaling pathway. These findings may prompt the potential application of TCDCA for MS therapy by suppressing astrocyte inflammation.

Taurochenodeoxycholic acid mediates cAMP-PKA-CREB signaling pathway

Taurochenodeoxycholic acid (TCDCA) is one of the main effective components of bile acid, playing critical roles in apoptosis and immune responses through the TGR5 receptor. In this study, we reveal the interaction between TCDCA and TGR5 receptor in TGR5-knockdown H1299 cells and the regulation of inflammation via the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA)-cAMP response element binding (CREB) signal pathway in NR8383 macrophages. In TGR5-knockdown H1299 cells, TCDCA significantly activated cAMP level via TGR5 receptor, indicating TCDCA can bind to TGR5; in NR8383 macrophages TCDCA increased cAMP content compared to treatment with the adenylate cyclase (AC) inhibitor SQ22536. Moreover, activated cAMP can significantly enhance gene expression and protein levels of its downstream proteins PKA and CREB compared with groups of inhibitors. Additionally, TCDCA decreased tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, IL-8 and IL-12 through nuclear factor kappa light chain enhancer of activated B cells (NF-κB) activity. PKA and CREB are primary regulators of anti-inflammatory and immune response. Our results thus demonstrate TCDCA plays an essential anti-inflammatory role via the signaling pathway of cAMP-PKA-CREB induced by TGR5 receptor.

Transcriptome investigation of anti-inflammation and immuno-regulation mechanism of taurochenodeoxycholic acid

BACKGROUND

Taurochenodeoxycholic acid (TCDCA) is one of the major active components in bile acid. It was proven to have inhibitory activities on inflammation and also participate in host immuno-regulation. TCDCA exerts anti-inflammatory and immuno-regulatory effects through the glucocorticoid receptor (GR) mediated genomic signaling pathway and the G protein-coupled bile acid receptor 5 (TGR5) mediated AC-cAMP-PKA signaling pathway. However, it is unclear whether GR or TGR5 plays an important role in the regulatory effects of TCDCA. In order to further investigate this effects mechanism of TCDCA, the research use the transcriptome to identify the major genes and pathway in the anti-inflammatory and immuno-regulatory effects.

METHODS

After the Fibroblast-like synoviocytes (FLS) being treated by different concentrations (10- 5, 10- 6 and 10- 7 M) of TCDCA for 12 h, the resulting mRNA was analyzed by RNA-seq. The differentially expressed genes were screened from sequencing results using bioinformatics techniques. In the next step, other published literature were referred in order to find out whether those genes mentioned above are related to inflammation. The final selected differentially expressed genes associated with inflammation were then validated by q-PCR and western blot assays.

RESULTS

Five genes associated with anti-inflammatory and immuno-regulatory effects, include Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Glutathione peroxidase 3 (GPX3), Serine/arginine-rich splicing factor-9 (SRSF9), Connective tissue growth factor (CTGF) and Cystatin B (CSTB) were identified. TCDCA at the concentrations of 10- 5, 10- 6 and 10- 7 M significantly (p < 0.05) up-regulate the mRNA and protein expression of SRSF9 and GPX3 and also up-regulate the mRNA expression of CSTB, CTGF and GAPDH. RNA-seq results of GPX3 and SRSF9 expression were consistent with q-PCR results, while q-PCR results of CTGF, GAPDH showed inconsistent with their RNA-seq results. Q-PCR result of CSTB expression also showed inconsistent with the RNA-seq result.

CONCLUSIONS

The anti-inflammatory and immuno-regulatory activities of TCDCA are proven to be related to the up-regulation expression of GPX3, SRSF9 and CSTB.