Abstract
Our previous studies have demonstrated that activation of α1-adrenergic receptors (ARs) increased interleukin-6 (IL-6) mRNA expression and protein secretion, which is probably an important yet unknown mechanism contributing to the regulation of cardiac function. Using Rat-1 fibroblasts stably transfected with the α1A-AR subtype and primary mouse neonatal cardiomyocytes, we elucidated the basic molecular mechanisms responsible for the α1-AR modulation of IL-6 expression. IL-6 mRNA production mediated by α1-AR peaked at 1 to 2 h. Studies of the mRNA decay rate indicated that α1-AR activation enhanced IL-6 mRNA stability. Analysis of IL-6 promoter activity using a series of deletion constructs indicated that α1-ARs enhanced IL-6 transcription through several transcriptional elements, including nuclear factor κB (NF-κB). Inhibition of α1-AR mediated IL-6 production and secretion by actinomycin D and the increase of intracellular IL-6 levels by α1-AR activation suggest that α1-AR mediated IL-6 secretion through de novo synthesis. Both IL-6 transcription and protein secretion mediated by α1-ARs were significantly reduced by chemical inhibitors for p38 mitogen-activated protein kinase (MAPK) and NF-κB and by a dominant-negative construct of p38 MAPK. Serum level of IL-6 was elevated in transgenic mice expressing a constitutively active mutant of the α1A-AR subtype but not in a similar mouse model expressing the α1B-AR subtype. Our results indicate that α1-ARs stimulated IL-6 expression and secretion through regulating both mRNA transcription and stability, involving p38 MAPK and NF-κB pathways.
Footnotes
-
This work was supported by an American Heart Association Beginning Grant in Aid [Grant 0865455D]; and the National Institutes of Health National Heart, Lung, and Blood Institute [Grant R01-HL61438].
-
ABBREVIATIONS: AR, adrenergic receptor; ActD, actinomycin D; MAPK, mitogen-activated protein kinase; AP-1, activated protein 1; Bay, Bay 11-7085 [(2E)-3-[[4-(1,1-dimethylethyl)phenyl]sulfonyl]-2-propene nitrile]; CAM, constitutively active mutant; CH, chelerythrine; CM, cardiomyocyte; CRE, cAMP response element; DMEM, Dulbecco's modified Eagle's medium; ELISA, enzyme-linked immunosorbent assay; Epi, epinephrine; ERK, extracellular signal-regulated kinase; Go, Go 6983 [3-[1-[3-(dimethylamino)propyl]-5-methoxy-1H-indol-3-yl]-4-(1H-indol-3-yl)-1H-pyrrole-2,5-dione]; IL, interleukin; NF-κB, nuclear factor-κB; PD, PD 98059 [2′-amino-3′-methoxyflavone]; SB, SB 203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole]; PKC, protein kinase C; RT-PCR, reverse transcription-polymerase chain reaction; WT, wild type; DN, dominant-negative; PBS, phosphate-buffered saline; ARE, adenine- and uridine-rich element.
- Accepted April 10, 2009.
- Received December 18, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|