ß2-receptor agonists salbutamol and terbutaline attenuated cytokine production by suppressing ERK pathway through cAMP in macrophages.

ß2-receptor agonists are used in the treatment of inflammatory obstructive lung diseases asthma and COPD as a symptomatic remedy, but they have been suggested to possess anti-inflammatory properties, also. ß2-receptor activation is considered to lead to the activation of ERK pathway through G-protein- and cAMP-independent mechanisms. In this study, we investigated the effects of ß2-receptor agonists salbutamol and terbutaline on the production of inflammatory factors in macrophages. We found that ß2-receptor agonists inhibited LPS-induced ERK phosphorylation and the production of MCP-1. A chemical cAMP analog 8-Br-cAMP also inhibited ERK phosphorylation and TNF and MCP-1 release. As expected, MAPK/ERK kinase (MEK)1/2 inhibitor PD0325901 inhibited ERK phosphorylation and suppressed both TNF and MCP-1 production. In conclusion, we suggest that ß2-receptor agonists salbutamol and terbutaline inhibit inflammatory gene expression partly by a mechanism dependent on cAMP leading to the inhibition of ERK signaling in macrophages. Observed anti-inflammatory effects of ß2-receptor agonists may contribute to the clinical effects of these drugs.

Anti-Inflammatory Effects of ß2-Receptor Agonists Salbutamol and Terbutaline Are Mediated by MKP-1.

Mitogen-activated protein kinase phosphatase 1 (MKP-1) expression is induced by inflammatory factors, and it is an endogenous suppressor of inflammatory response. MKP-1 expression is increased by PDE4 inhibitor rolipram suggesting that it is regulated by cAMP-enhancing compounds. Therefore, we investigated the effect of ß2-receptor agonists on MKP-1 expression and inflammatory response. We found that ß2-receptor agonists salbutamol and terbutaline, as well as 8-Br-cAMP, increased MKP-1 expression. Salbutamol and terbutaline also inhibited p38 MAPK phosphorylation and TNF production in J774 mouse macrophages. Interestingly, salbutamol suppressed carrageenan-induced paw inflammation in wild-type mice, but the effect was attenuated in MKP-1(-/-) mice. In conclusion, these data show that ß2-receptor agonists increase MKP-1 expression, which seems to mediate, at least partly, the observed anti-inflammatory effects of ß2-receptor agonists.

Regulation of Inflammatory Cytokine Production by MKP-5 in Macrophages.

Mitogen-activated protein kinases (MAPKs) include p38 MAPKs, c-Jun N-terminal kinases (JNKs) and Extracellular signal-regulated kinases (ERKs), and they regulate many cell processes, such as cell division, differentiation and release of inflammatory mediators. MAPK activity is controlled by mitogen-activated protein kinase phosphatases (MKPs), a phosphatase family with 11 members. MKP-1 is the most studied member of MKP family, and it is one of the anti-inflammatory factors induced by glucocorticoids. Less is known about the other MAPK phosphatases although they hold a promise as anti-inflammatory drug targets. In this study, we investigated the effect of MKP-5 on MAPK phosphorylation and cytokine production in J774 mouse macrophages. We used MKP-5 siRNA and an MKP-5 inhibitor (AS077234-4) to modulate MKP-5 function. We found that MKP-5 controlled p38 MAPK phosphorylation, but not that of JNK or ERK. In addition, the production of IL-6 and TNF was suppressed by MKP-5 in macrophages. Our results introduce a novel concept that compounds able to enhance MKP-5 expression and/or activity hold anti-inflammatory potential, because MKP-5 down-regulates the release of inflammatory mediators by controlling p38 MAPK activity.

Attenuation of TNF production and experimentally induced inflammation by PDE4 inhibitor rolipram is mediated by MAPK phosphatase-1.

BACKGROUND AND PURPOSE: 3',5'-Cyclic nucleotide PDE4 is expressed in several inflammatory and immune cells, and PDE4 catalyses the hydrolysis of cAMP to 5'AMP, down-regulating cAMP signalling in cells. MAPK phosphatase-1 (MKP-1) is an endogenous p38 MAPK signalling suppressor and limits inflammatory gene expression and inflammation. In the present study, we investigated the effect of a PDE4 inhibitor rolipram on MKP-1 expression and whether MKP-1 is involved in the anti-inflammatory effects of rolipram. EXPERIMENTAL APPROACH: The effect of rolipram on TNF production was investigated in J774 mouse macrophage cell line and in primary mouse peritoneal macrophages (PM) from wild-type (WT) and MKP-1(-/-) mice. We also investigated the effect of rolipram on carrageenan-induced paw inflammation in WT and MKP-1(-/-) mice. KEY RESULTS: MKP-1 expression was enhanced by rolipram, by a non-selective PDE inhibitor IBMX and by a cAMP analogue 8-Br-cAMP in J774 cells and in PM. Enhanced MKP-1 mRNA expression by rolipram was reversed by a PKA inhibitor. Rolipram, IBMX and 8-Br-cAMP also inhibited TNF production in activated macrophages. Accordingly, rolipram inhibited TNF production in PMs from WT mice but, interestingly, not in PMs from MKP-1(-/-) mice. Furthermore, rolipram attenuated carrageenan-induced paw inflammation in WT but not in MKP-1(-/-) mice. CONCLUSIONS AND IMPLICATIONS: PDE4 inhibitor rolipram was found to enhance the expression of MKP-1, and MKP-1 mediated, at least partly, the anti-inflammatory effects of PDE4 inhibition. The results suggest that compounds that enhance MKP-1 expression and/or MKP-1 activity hold potential as novel anti-inflammatory drugs.

Regulation of tristetraprolin expression by mitogen-activated protein kinase phosphatase-1.

Tristetraprolin (TTP) is an acute phase protein, and its expression is rapidly up-regulated by inflammatory signals, such as lipopolysaccharide (LPS) and cytokines. TTP regulates gene expression by governing the mRNA stability of its target genes, which include cytokines and growth factors. MAP kinase phosphatase-1 (MKP-1) is a nuclear phosphatase that inhibits p38 mitogen-activated protein kinase (MAPK) signaling. This study investigated the role of MKP-1 in TTP expression in A549 human lung epithelial cells, THP-1 human macrophages, J774 mouse macrophages, and primary mouse macrophages. TTP and MKP-1 expression was increased by cytokines or LPS. Silencing of MKP-1 by siRNA enhanced TTP expression in response to LPS, and LPS-induced TTP expression was increased in macrophages from MKP-1 (-/-) mice as compared with that in macrophages from wild-type animals. The inhibition of p38 MAPK by SB202190 reduced TTP expression. In conclusion, MKP-1 suppressed TTP expression by inhibiting p38 MAPK pathway.

The expression of interleukin-12 is increased by MAP kinase phosphatase-1 through a mechanism related to interferon regulatory factor 1.

Mitogen-activated protein kinase phosphatase-1 (MKP-1) is a nuclear tyrosine/threonine phosphatase that inhibits p38 mitogen-activated protein kinase (MAPK) activity. We and others have shown that MKP-1 deficiency leads to excessive activation of innate immunity and inflammatory gene expression. Surprisingly, the present study shows that MKP-1 is a positive regulator of IL-12 expression in macrophages suggesting a stimulatory effect on Th1 type immune response. In the present study, we found that LPS-induced expression of IL-12p40 was lower in primary mouse peritoneal macrophages (PMs) and bone marrow-derived macrophages from MKP-1 deficient mice than in cells from wild-type mice whereas TNF expression was enhanced as expected. Correspondingly, the inhibition of p38 MAPK by pharmacologic inhibitors BIRB 796 and SB 202190 enhanced LPS-induced IL-12p40 production. Silencing of interferon regulatory factor 1 (IRF1) by siRNA inhibited the expression of IL-12p40 in J774 macrophages, showing that IRF1 is an important factor regulating IL-12p40 expression. BIRB 796 enhanced LPS-induced expression of IRF1 in J774 macrophages and in PMs from wild-type mice, and IRF1 expression was reduced in PMs from MKP-1 deficient mice. In conclusions, our results show that MKP-1 increases and p38 MAPK decreases the expression of IL-12 by enhancing the expression of IRF1. MKP-1, through regulation of IRF1 and IL-12, therefore may be an important factor supporting the development of Th1 type of immune response and anti-microbial defense.