Induction of tyrosine hydroxylase by forskolin: modulation with age

Isoforskolin and forskolin attenuate lipopolysaccharide-induced inflammation through TLR4/MyD88/NF-κB cascades in human mononuclear leukocytes

The principal active component of isoforskolin (ISOF) is from the plant Coleus forskohlii, native to China, which has attracted much attention for its biological effects. We hypothesize that ISOF and forskolin (FSK) pretreatment attenuates inflammation induced by lipopolysaccharide (LPS) related to toll‐like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and nuclear factor kappa B (NF‐κB) signaling. Mononuclear leukocytes (MLs) from healthy donors' blood samples were separated by using density gradient centrifugation. Protein levels of TLR4, MyD88, and NF‐κB were detected using western blot and inflammatory cytokines interleukin (IL) 1β, IL‐2, IL‐6, IL‐21, IL‐23, tumor necrosis factor (TNF) α, and TNF‐β were tested by enzyme‐linked immunosorbent assay and Quantibody array in MLs. Our results showed that LPS augmented the protein levels of TLR4, MyD88, and NF‐κB in MLs and the production of IL‐1β, IL‐2, IL‐6, IL‐21, IL‐23, TNF‐α, and TNF‐β in supernatants of MLs. Despite treatment with ISOF and FSK prior to LPS, the protein levels of TLR4, MyD88, NF‐κB, IL‐1β, IL‐2, IL‐6, IL‐21, IL‐23, TNF‐α, and TNF‐β in MLs were apparently decreased. roflumilast (RF) and dexamethasone (DM) had a similar effect on MLs with ISOF and FSK. Our results, for the first time, have shown that ISOF and FSK attenuate inflammation in MLs induced by LPS through down‐regulating protein levels of IL‐1β and TNF‐α, in which TLR4/MyD88/NF‐κB signal pathway could be involved.

Vascular smooth muscle cell phosphodiesterase (PDE) 3 and PDE4 activities and levels are regulated by cyclic AMP in vivo

Prolonged incubation of several cell types, including cultured vascular smooth muscle cells (VSMC), with cyclic AMP-elevating agents increases cAMP phosphodiesterase (PDE) activity and levels. In this work, we describe for the first time an increase in arterial VSMC cAMP PDE activity and levels caused by cAMP-elevating agents when these agents are administered to rats in vivo. Injections of rats with dibutyryl cAMP (dbcAMP) or forskolin increased both PDE3 and PDE4 activities in aortic and femoral artery VSMC. Consistent with the idea that cAMP-elevating agents increased PDE3 and PDE4 activities by acting directly on VSMC, local delivery of dbcAMP or forskolin to femoral arteries using a pluronic gel-based approach increased femoral artery VSMC PDE3 and PDE4 activities to levels similar to those observed after injection of these agents. Consistent with a role for de novo mRNA and protein synthesis in the cAMP-elevating agent induced increase in PDE3 and PDE4, 1) systemic administration of forskolin increased PDE3A, PDE3B, and PDE4D mRNA levels in aortic VSMC and femoral artery VSMC, 2) local delivery of dbcAMP increased PDE3A, PDE3B, and PDE4D3 protein levels in femoral artery VSMC, and 3) local administration of either actinomycin D or cycloheximide attenuated the effect of dbcAMP. In addition, our results indicate that the PDE3 and PDE4 variants increased by cAMP-elevating agents in arterial VSMC in situ were distinct from those elevated by these agents in cultured arterial VSMC. Consistent with the effect of increased VSMC cAMP PDE on blood vessel function, inhibition of PDE3 and PDE4 activities potentiated the relaxant effect of forskolin in dbcAMP-treated femoral artery rings to a greater extent than in untreated control blood vessels. We propose that our findings are consistent with the concept that cAMP regulates VSMC cAMP PDE activity and levels in vivo and that VSMC phenotype influences the choice of cAMP PDE variant that is elevated. Our findings are discussed in the context that agents aimed at specific PDE3 or PDE4 variants could perhaps allow greater control of cAMP-mediated regulation of VSMC behaviors that are phenotype-dependent.

[Effect of cAMP on the function of endothelial cells and fibromuscular proliferation after the injury of the carotid and coronary arteries in a porcine model]

INTRODUCTION AND OBJECTIVE

Reendothelization of damaged blood vessels protects against the vascular injury response. We evaluated in vivo whether a systemic increase in cAMP accelerates reendothelization and attenuates intimal hyperplasia in injured swine carotid and coronary arteries.

METHODS

Both carotid arteries of 10 swines were subjected to balloon injury. Five animals had been treated with 2 ml (10 mg) of Forskolin, an activator of the adenylate cyclase, and another 5 with 2 ml of saline solution. These animals were sacrificed at day 8, and carotid artery reendothelization was evaluated. The descendent coronary (DC) artery of another 19 pigs was injured by atherotome. Nine animals had been treated with 2 ml of Forskolin, and another 10 with 2 ml of saline solution. These animals were sacrificed at day 28, with myointimal proliferation and arterial geometric remodelation being evaluated. Likewise, in these animals intracellular cAMP levels were measured at baseline and 28 and 60 minutes after saline solution or Forskolin administration and 90 min after arterial injury.

RESULTS

Eight days after balloon injury, carotid artery reendothelization was greater in the Forskolin-treated group compared with the control group (p = 0.02), and the number of CD31 positive cells was statistically increased in the treated group (38 +/- 11 cells) versus controls (11 +/- 9 cells). Although the degree of vascular injury caused by atherotome was similar in all of the arteries in the control group, restenosis was only observed in 40% of these animals. Correlation analysis demonstrated that intracellular cAMP may condition arterial geometric remodeling and the diameter of the lumen after vascular injury.

CONCLUSION

Our results suggest that cAMP may promote reendothelization and attenuate fibromuscular proliferation.