Differential Expression and Activation of p38 Mitogen-Activated Protein Kinase α, β, γ, and δ in Inflammatory Cell Lineages

Abstract

Four p38 mitogen-activated protein kinases (p38α, β, γ, δ) have been described. To understand the role of p38 family members in inflammation, we determined their relative expression in cells that participate in the inflammatory process. Expression was measured at the level of mRNA by reverse-transcriptase PCR and protein by Western blot analysis. p38α was the dominant form of p38 in monocytes; expression of p38δ was low and p38β was undetected. In macrophages, p38α and p38δ were abundant, but p38β was undetected. p38α and p38δ were also expressed by neutrophils, CD4+ T cells, and endothelial cells. Again, p38β was not detected in neutrophils, although low amounts were present in CD4+ T cells. In contrast, p38β was abundant in endothelial cells. p38γ protein was not detected in any cell type, although p38γ mRNA was present in endothelial cells. Immunokinase assays showed a strong activation of p38α and a lesser activation of p38δ in LPS-stimulated macrophages. Abs specific for mono- and dual-phophorylated forms of p38 suggested that LPS induces dual phosphorylation of p38α, but primarily mono-phosphorylation of p38δ. IL-1β activated p38α and p38β in endothelial cells. However, p38α was the more activated form based on kinase assays and phosphorylation analysis. Expression and activation patterns of p38α in macrophages and endothelial cells suggest that p38α plays a major role in the inflammatory response. Additional studies will be needed to define the contribution of p38δ to macrophage, neutrophil, and T cell functions, and of p38β to signaling in endothelial cells and T cells.

Chemical Knockdown of Phosphorylated p38 Mitogen-Activated Protein Kinase (MAPK) as a Novel Approach for the Treatment of Alzheimer′s Disease

“…PRZ-18002 also decreased the phosphorylation level of downstream targets of p38, MK2, and HSP27, in a concentration-dependent manner (Figure D). In addition, PRZ-18002 showed excellent kinase selectivity against a panel of 96 different kinases (Figure S3), which are considered to be functionally or structurally similar to p38 based on the kinome analysis and the cross reactivity analysis with other p38 inhibitors such as SB-203580, BIRB-796, and Neflamapimod (VX-745) . We also observed a substantial reduction in the protein level of p-p38 compared with other MAPKs, such as ERK, JNK, and MEK, in their phosphorylated forms (Figure S4).…”

“…In addition, PRZ-18002 showed excellent kinase selectivity against a panel of 96 different kinases (Figure S3), which are considered to be functionally or structurally similar to p38 based on the kinome analysis and the cross reactivity analysis with other p38 inhibitors such as SB-203580, BIRB-796, and Neflamapimod (VX-745). 19 We also observed a substantial reduction in the protein level of p-p38 compared with other MAPKs, such as ERK, JNK, and MEK, in their phosphorylated forms (Figure S4). In addition, the phosphorylation status of MKK3 and MKK4 kinases, upstream MAPK kinases (MAPKKs) responsible for the phosphorylation of p38, did not show any significant change upon treatment with PRZ-18002 (Figure 1E).…”

CHF6297: a novel potent and selective p38 MAPK inhibitor with robust anti-inflammatory activity and suitable for inhaled pulmonary administration as dry powder

“…The p38 mitogen-activated protein kinase (MAPK) signaling pathway plays an essential role in inflammation, especially in the regulation and activation of key proinflammatory mediators. There are four known human isoforms of p38 MAPK, namely, p38α, (MAPK14) p38β, (MAPK11) p38γ (MAPK12), and p38δ (MAPK13), which differ in cell and tissue distribution, regulation of kinase activation, and phosphorylation of downstream substrates ( Hale et al, 1999 ; Dominguez et al, 2005 ). These enzymes also differ in sensitivity to p38 MAPK inhibitors ( Dominguez et al, 2005 ).…”

p38 mitogen‐activated protein kinase: Functions and targeted therapy in diseases

“…P38MAPK pathway is important in proinflammatory cytokines such as TNF‐α, IL‐1, IL‐2, IL‐6, IL‐7, and so on, 95 and the four subtypes of p38MAPK are also differentially expressed and activated in different inflammatory cells 96 . In monocytes, p38α was the dominant expression form, but p38δ expression was low and p38β was not detected.…”