Cooperative and distinct functions of MK2 and MK3 in the regulation of the macrophage transcriptional response to lipopolysaccharide

MAPK activated kinase 2 inhibition shifts the chemokine signature in arthritis synovial fluid mononuclear cells from CXCR3 to CXCR2

BACKGROUND

The development of novel treatment strategies of immune-mediated inflammatory arthritis (IMIA) is still a clinical unmet need. The mitogen-activated protein kinase (MAPK) pathway is activated by environmental stressors, growth factors and inflammatory cytokines. However, the inhibition of central MAPK proteins has so far had undesirable side effects. The MAPK-activated protein kinase 2 (MK2) is a downstream mediator in the MAPK signaling pathway.

OBJECTIVES

The objective of this study was to explore the effects of a small molecule inhibiting MK2 on synovial fluid mononuclear cells from patients with IMIA.

METHODS

Synovial fluid mononuclear cells (SFMCs) were obtained from a study population consisting of patients with active rheumatoid arthritis (RA), peripheral spondyloarthritis (SpA) or psoriatic arthritis (PsA) with at least one swollen joint (for obtaining synovial fluid) (n = 11). SFMCs were cultured for 48 h with and without the MK2 inhibitor CC0786512 at 1000 nM, 333 nM and 111 nMand cell free supernatants were harvested and frozen before they were analyzed by the Olink proseek multiplex interferon panel.

RESULTS

In SFMCs cultured for 48 h, the MK2 inhibitor decreased the production of chemokine (C-X-C motif) ligand 9 (CXCL9) (P < 0.001), CXCL10 (P < 0.01), hepatocyte growth factor (HGF) (P < 0.01), CXCL11 (P < 0.01), tumor necrosisfactor-like weak inducer of apoptosis (TWEAK) (P < 0.05), and interleukin 12B (IL-12B) (P < 0.05) and increased the production of CXCL5 (P < 0.0001), CXCL1 (P < 0.0001), CXCL6 (P < 0.001), transforming growthfactoralpha (TGFα) (P = 0.01), monocyte-chemotactic protein 3 (MCP-3) (P < 0.01), latency-associated peptide (LAP) TGFβ (P < 0.05) dose-dependently.

CONCLUSIONS

This study reveals the downstream effects of MK2 inhibition on the secretory profile of SFMCs. Specifically, C-X-C motif chemokine receptors 3 (CXCR3) chemokines were decreased and CXCR2 chemokines were increased. This shift in the chemokine milieu may be one of the mechanisms behind the anti-inflammatory effects of MK2 inhibitors.

Mosloflavone-Resveratrol Hybrid TMS-HDMF-5z Exhibits Potent In Vitro and In Vivo Anti-Inflammatory Effects Through NF-κB, AP-1, and JAK/STAT Inactivation

TMS-HDMF-5z is a hybrid of the natural products mosloflavone and resveratrol. It was discovered to show potent inhibitory effects against lipopolysaccharide (LPS)-induced production of inflammatory mediators in RAW 264.7 macrophages. However, its mechanism of action is unknown. Hence this study aimed to demonstrate and explore in vitro and in vivo anti-inflammatory effects of TMS-HDMF-5z and its mechanism of action employing RAW 264.7 macrophages and carrageenan-induced hind paw edema. This work revealed that TMS-HDMF-5z suppressed the LPS-induced inducible nitric-oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the protein, mRNA, and promoter binding levels and tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6, and interferon-β (IFN-β) at the mRNA expression in RAW 264.7 macrophages. The results showed that TMS-HDMF-5z reduced the transcription and DNA binding activities of nuclear factor-κB (NF-κB) through inhibiting nuclear translocation of p65 and phosphorylation of κB inhibitor α (IκBα), IκB kinase (IKK), and TGF-β activated kinase 1 (TAK1). Additionally, TMS-HDMF-5z attenuated the LPS-induced transcriptional and DNA binding activities of activator protein-1 (AP-1) by suppressing nuclear translocation of phosphorylated c-Fos, c-Jun, and activating transcription factor 2 (ATF2). TMS-HDMF-5z also reduced the LPS-induced phosphorylation of Janus kinase 1/2 (JAK1/2), signal transducers and activators of transcription 1/3 (STAT1/3), p38 mitogen-activated protein kinase (MAPK), and MAPK-activated protein kinase 2 (MK2). In rats, TMS-HDMF-5z alleviated carrageenan-induced hind paw edema through the suppressing iNOS and COX-2 via NF-κB, AP-1, and STAT1/3 inactivation. Collectively, the TMS-HDMF-5z-mediated inhibition of NF-κB, AP-1, and STAT1/3 offer an opportunity for the development of a potential treatment for inflammatory diseases.

PTIP governs NAD+ metabolism by regulating CD38 expression to drive macrophage inflammation

NAD⁺ metabolism is involved in many biological processes. However, the underlying mechanism of how NAD⁺ metabolism is regulated remains elusive. Here, we find that PTIP governs NAD⁺ metabolism in macrophages by regulating CD38 expression and is required for macrophage inflammation. Through integrating histone modifications with NAD⁺ metabolic gene expression profiling, we identify PTIP as a key factor in regulating CD38 expression, the primary NAD⁺-consuming enzyme in macrophages. Interestingly, we find that PTIP deletion impairs the proinflammatory response of primary murine and human macrophages, promotes their metabolic switch from glycolysis to oxidative phosphorylation, and alters NAD⁺ metabolism via downregulating CD38 expression. Mechanistically, an intronic enhancer of CD38 is identified. PTIP regulates CD38 expression by cooperating with acetyltransferase p300 in establishing the CD38 active enhancer with enriched H3K27ac. Overall, our findings reveal a critical role for PTIP in fine-tuning the inflammatory responses of macrophages via regulating NAD⁺ metabolism.

MAPK-Activated Protein Kinases: Servant or Partner?

Mitogen-activated protein kinase (MAPK)-activated protein kinases (MAPKAPKs) are defined by their exclusive activation by MAPKs. They can be activated by classical and atypical MAPKs that have been stimulated by mitogens and various stresses. Genetic deletions of MAPKAPKs and availability of highly specific small-molecule inhibitors have continuously increased our functional understanding of these kinases. MAPKAPKs cooperate in the regulation of gene expression at the level of transcription; RNA processing, export, and stability; and protein synthesis. The diversity of stimuli for MAPK activation, the cross talk between the different MAPKs and MAPKAPKs, and the specific substrate pattern of MAPKAPKs orchestrate immediate-early and inflammatory responses in space and time and ensure proper control of cell growth, differentiation, and cell behavior. Hence, MAPKAPKs are promising targets for cancer therapy and treatments for conditions of acute and chronic inflammation, such as cytokine storms and rheumatoid arthritis. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Mitogen-activated protein kinase-activated protein kinase-2 (MK2) and its role in cell survival, inflammatory signaling, and migration in promoting cancer

Cancer and the immune system share an intimate relationship. Chronic inflammation increases the risk of cancer occurrence and can also drive inflammatory mediators into the tumor microenvironment enhancing tumor growth and survival. The p38 MAPK pathway is activated both acutely and chronically by stress, inflammatory chemokines, chronic inflammatory conditions, and cancer. These properties have led to extensive efforts to find effective drugs targeting p38, which have been unsuccessful. The immediate downstream serine/threonine kinase and substrate of p38 MAPK, mitogen-activated-protein-kinase-activated-protein-kinase-2 (MK2) protects cells against stressors by regulating the DNA damage response, transcription, protein and messenger RNA stability, and motility. The phosphorylation of downstream substrates by MK2 increases inflammatory cytokine production, drives an immune response, and contributes to wound healing. By binding directly to p38 MAPK, MK2 is responsible for the export of p38 MAPK from the nucleus which gives MK2 properties that make it unique among the large number of p38 MAPK substrates. Many of the substrates of both p38 MAPK and MK2 are separated between the cytosol and nucleus and interfering with MK2 and altering this intracellular translocation has implications for the actions of both p38 MAPK and MK2. The inhibition of MK2 has shown promise in combination with both chemotherapy and radiotherapy as a method for controlling cancer growth and metastasis in a variety of cancers. Whereas the current data are encouraging the field requires the development of selective and well tolerated drugs to target MK2 and a better understanding of its effects for effective clinical use.

Acute-phase protein synthesis: a key feature of innate immune functions of the liver

The expression of acute-phase proteins (APP's) maintains homeostasis and tissue repair, but also represents a central component of the organism's defense strategy, especially in the context of innate immunity. Accordingly, an inflammatory response is accompanied by significant changes in the serum protein composition, an aspect that is also used diagnostically. As the main site of APP synthesis the liver is constantly exposed to antigens or pathogens via blood flow, but also to systemic inflammatory signals originating either from the splanchnic area or from the circulation. Under both homeostatic and acute-phase response (APR) conditions the composition of APP's is determined by the pattern of regulatory mediators derived from the systemic circulation or from local cell populations, especially liver macrophages. The key regulators mentioned here most frequently are IL-1β, IL-6 and TNF-α. In addition to a variety of molecular mediators described mainly on the basis of in vitro studies, recent data emphasize the in vivo relevance of cellular key effectors as well as molecular key mediators and protein modifications for the regulation and function of APP's. These are aspects, on which the present review is primarily focused.

The MK2 pathway is linked to G-CSF, cytokine production and metastasis in gastric cancer: a novel intercorrelation analysis approach

Background

Gastric cancer is associated with chronic inflammation, but there is still much to understand about the tumor microenvironment and the underlying tumor-promoting mechanisms. The Map kinase-activated protein kinase 2 (MK2) pathway is a regulator of inflammatory cytokine production that we have been studying in gastrointestinal cancers. Here, we set out to determine the significance of this gene in gastric cancer along with its downstream mediators and if there were differences in the primary tumors with and without metastasis.

Methods

Human gastric cancer tissues with and without metastasis were examined for MK2 expression and cytokine profile in organ culture supernatants. Advanced statistical methods including a lower triangular correlation matrix, novel rooted correlation network, linear and logistic regression modeling along with Kruskal–Wallis testing with Sidak correction for multiple testing were applied to gain understanding of cytokines/chemokines linked to metastasis.

Results

The MK2 pathway is strongly linked with metastasis and a panel of cytokines. Gene expression was able to classify gastric cancer metastasis 85.7% of the time. A significant association with a panel of cytokines was found, including G-CSF, GM-CSF, Mip-1β, IFN-α, MCP-1, IL-1β, IL-6, and TNF-α. Mip-1β was found to have the strongest association with MK2 and metastasis after Sidak correction for multiple testing.

Conclusions

MK2 gene expression and a novel associated cytokine panel are linked to gastric cancer metastasis. G-CSF is the strongest cytokine to differentiate between metastasis and non-metastasis patients and had the lowest P value, while Mip-1β showed the strongest association with MK2 and metastasis after Sidak correction. MK2 and associated cytokines are potential biomarkers for gastric cancer metastasis. The novel intercorrelation analysis approach is a promising method for understanding the complex nature of cytokine/chemokine regulation and links to disease outcome.