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Redox regulation of cAMP levels by ascorbate in 1,25-dihydroxy- vitamin D3-induced differentiation of HL-60 cells.

ABSTRACT: 1alpha,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] induces differentiation to monocyte-macrophage lineage of several leukaemic cell lines such as HL-60, U937, M1 and Mono Mac 6. Ascorbate also modulates growth and differentiation of different animal cells in culture. We have previously reported the stimulating effect of ascorbate on 1, 25-(OH)2D3-induced HL-60 cell differentiation. We show here that 1, 25-(OH)2D3 induces a transient increase in cAMP levels in these cells, and ascorbate significantly increases these cAMP levels. Ascorbate alone does not have any effect. Other cAMP-increasing agents such as isobutylmethylxanthine, forskolin and prostaglandin E2 maintain high levels of cAMP at 48 h of incubation and also enhance differentiation along the monocytic pathway induced by 1, 25-(OH)2D3, as revealed by specific differentiation markers, demonstrating the importance of cAMP in the differentiation process. It is also shown that the presence of ascorbate and its free radical (AFR) during 1,25-(OH)2D3-induced differentiation significantly decreases cytoplasmic NADH levels compared with those induced by 1,25-(OH)2D3 in HL-60 cells. The results indicate that NADH is an inhibitor of adenylate cyclase in these cells. AFR is an electron acceptor of the trans-plasma-membrane electron-transport system, and NADH is the electron donor. Through this system, ascorbate and AFR keep levels of NADH low, thereby decreasing its inhibitory effect on adenylate cyclase activity and so increasing cAMP synthesis. We also demonstrate that other ascorbate derivatives, such as ascorbate 2-phosphate and dehydroascorbate, both of which are unable to produce AFR, do not alter intracellular NADH levels during 1, 25-(OH)2D3-induced differentiation. Also, ascorbate and AFR increase specific differentiation markers (CD14 and NitroBlue Tetrazolium reduction) but neither ascorbate 2-phosphate nor dehydroascorbate show this enhancing activity. In summary, we propose that the effect of ascorbate on 1,25-(OH)2D3-induced differentiation of HL-60 cells can be explained by redox regulation of the cAMP pathway.

SUBMITTER: Lopez-Lluch G

PROVIDER: S-EPMC1219316 | biostudies-other | 1998 Apr

REPOSITORIES: biostudies-other

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Project description:BackgroundGouty arthritis (GA) is a common type of inflammatory arthritis. Recent studies demonstrated that 1,25-dihydroxy vitamin D3 (1,25(OH) 2 VD3) and vitamin D3 receptor (VD-R) play a protective role in acute inflammation, but interleukin-22(IL-22) promotes inflammation, especially for arthritis. However, our understanding of the responses of 1,25(OH) 2VD3 and IL-22 to gout was still unclear. Presently, in-depth metabolomics, bioinformatics and clinical characteristics analyses were performed to elucidate the pathogenesis and valuable clinical indicators of gouty arthritis.MethodsPeripheral venous blood was taken for investigation. The levels of IL-22 and 1,25(OH)2VD3 were determined in patient's plasma via ELISA, and the mRNA levels of IL-22 and VD-R were measured via qRT-PCR. The interaction network of VD-R and IL22 were constructed by the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING), and the biological function of the related proteins were analyzed by Clusterprofiler Metabolomics were performed to decipher the metabolic variations of GA.ResultsThe levels of VD-R and 1,25(OH) 2 VD3 were identified to be low. What,s more, GA patients were reported to have high expression of IL-22. And IL-22 levels positively correlated with C-reactiveprotein (CRP) serum levels in the bivariate correlation analysis, whereas the level of 1,25(OH) 2VD3 negatively correlated with that of CRP. GO and KEGG analyses revealed that IL-22 and 1,25(OH) 2 VD3 were involved in stress immunity and inflammatory responses. These pathways are known to play a role in GA pathogenesis. Meanwhile, the metabolic profiles of GA serum showed that the increase in various amino acids and uric acid are involved in GA pathogenesis. Importantly, VD-R and IL22 closely correlated with the level of key metabolites uric acid, whose increase promoted the occurrence of GA.ConclusionGA patients have low levels of VD-R and 1,25(OH) 2 VD3, and high levels of IL-22 together with various amino acids and uric acid. The levels of IL-22 and 1,25(OH) 2VD3 were positively and negatively correlated with C-reactive protein (CRP) serum levels, respectively. Both IL-22 and 1,25(OH) 2 VD3 functioned in GA-related immune and inflammatory responses, and closely correlated with the level of GA-related uric acid. Overall, IL-22, VD-R and 1,25(OH) 2 VD3 play functionally important roles in inflammatory responses and are relevant to gout pathogenesis.

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Redox regulation of cAMP levels by ascorbate in 1,25-dihydroxy- vitamin D3-induced differentiation of HL-60 cells.

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