Differential regulation of anti-inflammatory genes by p38 MAP kinase and MAP kinase kinase 6

The Role of p38 Mitogen-Activated Protein Kinase-Mediated F-Actin in the Acupuncture-Induced Mitigation of Inflammatory Pain in Arthritic Rats

The analgesic efficacy of acupuncture has been widely recognized. However, the mechanism by which manual acupuncture-generated mechanical stimuli translate into biological signals remains unclear. This study employed a CFA-induced inflammatory pain rat model. Acupuncture intervention was then performed following standardized procedures. Enzyme-linked immunosorbent assay (ELISA) assessed inflammatory cytokines levels, while immunofluorescence and qRT-PCR screened the level of p38 and F-actin expression in the ST36 acupoint area of rats. Results indicated increased inflammatory factors, including IL-1β and TNFα, with reduced paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) in CFA rats compared to unmodeled rats. After acupuncture intervention, the heightened expression level of F-actin and p38 mRNA and the phosphorylation of p38 in the acupoint area was observed alongside decreased inflammatory factors in diseased ankle joints. The application of lifting and thrusting manipulations further enhanced the effect of acupuncture, in which the molecular expression level of muscle and connective tissue increased most significantly, indicating that these two tissues play a major role in the transformation of acupuncture stimulation. Moreover, antagonizing p38 expression hindered acupuncture efficacy, supporting the hypothesis that p38 MAPK-mediated F-actin transduces mechanical signals generated by acupuncture and related manipulation into biological signals.

Sex Dependent Disparities in the Central Innate Immune Response after Moderate Spinal Cord Contusion in Rat

Subacute spinal cord injury (SCI) displays a complex pathophysiology associated with pro-inflammation and ensuing tissue damage. Microglia, the resident innate immune cells of the CNS, in concert with infiltrating macrophages, are the primary contributors to SCI-induced inflammation. However, subpopulations of activated microglia can also possess immunomodulatory activities that are essential for tissue remodeling and repair, including the production of anti-inflammatory cytokines and growth factors that are vital for SCI recovery. Recently, reports have provided convincing evidence that sex-dependent differences exist in how microglia function during CNS pathologies and the extent to which these cells contribute to neurorepair and endogenous recovery. Herein we employed flow cytometry and immunohistochemical methods to characterize the phenotype and population dynamics of activated innate immune cells within the injured spinal cord of age-matched male and female rats within the first week (7 days) following thoracic SCI contusion. This assessment included the analysis of pro- and anti-inflammatory markers, as well as the expression of critical immunomodulatory kinases, including P38 MAPK, and transcription factors, such as NFκB, which play pivotal roles in injury-induced inflammation. We demonstrate that activated microglia from the injured spinal cord of female rats exhibited a significantly diminutive pro-inflammatory response, but enhanced anti-inflammatory activity compared to males. These changes included lower levels of iNOS and TLR4 expression but increased levels of ARG-1 and CD68 in females after SCI. The altered expression of these markers is indicative of a disparate secretome between the microglia of males and females after SCI and that the female microglia possesses higher phagocytic capabilities (increased CD68). The examination of immunoregulatory kinases and transcription factors revealed that female microglia had higher levels of phosphorylated P38Thr180/Tyr182 MAPK and nuclear NFκB pp50Ser337 but lower amounts of nuclear NFκB pp65Ser536, suggestive of an attenuated pro-inflammatory phenotype in females compared to males after SCI. Collectively, this work provides novel insight into some of the sex disparities that exist in the innate immune response after SCI and indicates that sex is an important variable when designing and testing new therapeutic interventions or interpretating positive or negative responses to an intervention.

Stress signaler p38 mitogen-activated kinase activation: a cause for concern?

Oxidative stress (OS) induced activation of p38 mitogen-activated kinase (MAPK) and cell fate from p38 signaling was tested using the human fetal membrane's amnion epithelial cells (AEC). We created p38 KO AEC using the CRISPR/Cas9 approach and tested cell fate in response to OS on an AEC-free fetal membrane extracellular matrix (ECM). Screening using image CyTOF indicated OS causing epithelial-mesenchymal transition (EMT). Further testing revealed p38 deficiency prevented AEC senescence, EMT, cell migration, and inflammation. To functionally validate in vitro findings, fetal membrane-specific conditional KO (cKO) mice were developed by injecting Cre-recombinase encoded exosomes intra-amniotically into p38αloxP/loxP mice. Amnion membranes from p38 cKO mice had reduced senescence, EMT, and increased anti-inflammatory IL-10 compared with WT animals. Our study suggested that overwhelming activation of p38 in response to OS inducing risk exposures can have an adverse impact on cells, cause cell invasion, inflammation, and ECM degradation detrimental to tissue homeostasis.

Activation of the MKK3-p38-MK2-ZFP36 Axis by Coronavirus Infection Restricts the Upregulation of AU-Rich Element-Containing Transcripts in Proinflammatory Responses

Coronavirus infections induce the expression of multiple proinflammatory cytokines and chemokines. We have previously shown that in cells infected with gammacoronavirus infectious bronchitis virus (IBV), interleukin 6 (IL-6), and IL-8 were drastically upregulated, and the MAP kinase p38 and the integrated stress response pathways were implicated in this process. In this study, we report that coronavirus infection activates a negative regulatory loop that restricts the upregulation of a number of proinflammatory genes. As revealed by the initial transcriptomic and subsequent validation analyses, the anti-inflammatory adenine-uridine (AU)-rich element (ARE)-binding protein, zinc finger protein 36 (ZFP36), and its related family members were upregulated in cells infected with IBV and three other coronaviruses, alphacoronaviruses porcine epidemic diarrhea virus (PEDV), human coronavirus 229E (HCoV-229E), and betacoronavirus HCoV-OC43, respectively. Characterization of the functional roles of ZFP36 during IBV infection demonstrated that ZFP36 promoted the degradation of transcripts coding for IL-6, IL-8, dual-specificity phosphatase 1 (DUSP1), prostaglandin-endoperoxide synthase 2 (PTGS2) and TNF-α-induced protein 3 (TNFAIP3), through binding to AREs in these transcripts. Consistently, knockdown and inhibition of JNK and p38 kinase activities reduced the expression of ZFP36, as well as the expression of IL-6 and IL-8. On the contrary, overexpression of mitogen-activated protein kinase kinase 3 (MKK3) and MAPKAP kinase-2 (MK2), the upstream and downstream kinases of p38, respectively, increased the expression of ZFP36 and decreased the expression of IL-8. Taken together, this study reveals an important regulatory role of the MKK3-p38-MK2-ZFP36 axis in coronavirus infection-induced proinflammatory response. IMPORTANCE Excessive and uncontrolled induction and release of proinflammatory cytokines and chemokines, the so-called cytokine release syndrome (CRS), would cause life-threatening complications and multiple organ failure in severe coronavirus infections, including severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS) and COVID-19. This study reveals that coronavirus infection also induces the expression of ZFP36, an anti-inflammatory ARE-binding protein, promoting the degradation of ARE-containing transcripts coding for IL-6 and IL-8 as well as a number of other proteins related to inflammatory response. Furthermore, the p38 MAP kinase, its upstream kinase MKK3 and downstream kinase MK2 were shown to play a regulatory role in upregulation of ZFP36 during coronavirus infection cycles. This MKK3-p38-MK2-ZFP36 axis would constitute a potential therapeutic target for severe coronavirus infections.

Butorphanol Promotes Macrophage Phenotypic Transition to Inhibit Inflammatory Lung Injury via κ Receptors

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is characterized by diffuse inflammation of the lung parenchyma and refractory hypoxemia. Butorphanol is commonly used clinically for perioperative pain relief, but whether butorphanol can regulate LPS-induced alveolar macrophage polarization is unclear. In this study, we observed that butorphanol markedly attenuated sepsis-induced lung tissue injury and mortality in mice. Moreover, butorphanol also decreased the expression of M1 phenotype markers (TNF-α, IL-6, IL-1β and iNOS) and enhanced the expression of M2 marker (CD206) in alveolar macrophages in the bronchoalveolar lavage fluid (BALF) of LPS-stimulated mice. Butorphanol administration reduced LPS-induced numbers of proinflammatory (M1) macrophages and increased numbers of anti-inflammatory (M2) macrophages in the lungs of mice. Furthermore, we found that butorphanol-mediated suppression of the LPS-induced increases in M1 phenotype marker expression (TNF-α, IL-6, IL-1β and iNOS) in bone marrow-derived macrophages (BMDMs), and this effect was reversed by κ-opioid receptor (KOR) antagonists. Moreover, butorphanol inhibited the interaction of TLR4 with MyD88 and further suppressed NF-κB and MAPKs activation. In addition, butorphanol prevented the Toll/IL-1 receptor domain-containing adaptor inducing IFN-β (TRIF)-mediated IFN signaling pathway. These effects were ameliorated by KOR antagonists. Thus, butorphanol may promote macrophage polarization from a proinflammatory to an anti-inflammatory phenotype secondary to the inhibition of NF-κB, MAPKs, and the TRIF-mediated IFN signaling pathway through κ receptors.

Extract From Plectranthus amboinicus Inhibit Maturation and Release of Interleukin 1β Through Inhibition of NF-κB Nuclear Translocation and NLRP3 Inflammasome Activation

Uncontrolled inflammation may produce massive inflammatory cytokines, in which interleukin 1β (IL-1β) plays a key role, resulting in tissue damage and serious disorders. The activation of NLRP3 inflammasome is one of the major mechanisms in maturation and release of IL-1β. Plectranthus amboinicus is a perennial herb. Several pharmacological activities of natural components and crude extracts from P. amboinicus have been reported including anti-inflammation; however, the underlying mechanism is not clear. Phorbol-12-myristate 13-acetate-differentiated THP-1 monocytic leukemia cells were used as a reliable model in this study to examine the effect on inflammasome signaling pathway by PA-F4, an extract from Plectranthus amboinicus. PA-F4 inhibited ATP-induced release of caspase-1, IL-1β, and IL-18 from lipopolysaccharides (LPS)-primed cells. PA-F4 induced a concentration-dependent inhibition of both ASC dimerization and oligomerization in cells under LPS priming plus ATP stimulation. Co-immunoprecipitation of NLRP3 and ASC demonstrated that PA-F4 significantly blunted the interaction between NLRP3 and ASC. Furthermore, PA-F4 completely abolished ATP-induced K⁺ efflux reaction in LPS-primed cells. Taken together, PA-F4 displayed an inhibitory activity on NLRP3 inflammasome activation. Moreover, PA-F4 also inhibited LPS-induced p65 NF-κB activation, suggesting an inhibitory activity on LPS priming step. Further identification showed that rosmarinic acid, cirsimaritin, salvigenin, and carvacrol, four constituents in PA-F4, inhibited LPS-induced IL-6 release. In contrast, rosmarinic acid, cirsimaritin and carvacrol but not salvigenin inhibited ATP-induced caspase-1 release from LPS-primed cells. In conclusion, PA-F4 displayed an inhibitory activity on activation of NLRP3 inflammasome. PA-F4 inhibited LPS priming step through block of p65 NF-κB activation. It also inhibited ATP-induced signaling pathways in LPS-primed cells including the inhibition of both ASC dimerization and oligomerization, K⁺ efflux reaction, and the release reaction of caspase-1, IL-1β, and IL-18. Rosmarinic acid, cirsimaritin, salvigenin, and carvacrol could partly explain PA-F4-mediated inhibitory activity on blocking the activation of NLRP3 inflammasome.

Selection of reliable reference genes for the normalisation of gene expression levels following time course LPS stimulation of murine bone marrow derived macrophages

Background

Macrophages are key players in the initiation, perpetuation and regulation of both innate and adaptive immune responses. They largely perform these roles through modulation of the expression of genes, especially those encoding cytokines. Murine bone marrow derived macrophages (BMDMs) are commonly used as a model macrophage population for the study of immune responses to pro-inflammatory stimuli, notably lipopolysaccharide (LPS), which may be pertinent to the human situation. Evaluation of the temporal responses of LPS stimulated macrophages is widely conducted via the measurement of gene expression levels by RT-qPCR. While providing a robust and sensitive measure of gene expression levels, RT-qPCR relies on the normalisation of gene expression data to a stably expressed reference gene. Generally, a normalisation gene(s) is selected from a list of “traditional” reference genes without validation of expression stability under the specific experimental conditions of the study. In the absence of such validation, and given that many studies use only a single reference gene, the reliability of data is questionable.

Results

The stability of expression levels of eight commonly used reference genes was assessed during the peak (6 h) and resolution (24 h) phases of the BMDM response to LPS. Further, this study identified two additional genes, which have not previously been described as reference genes, and the stability of their expression levels during the same phases of the inflammatory response were validated. Importantly, this study demonstrates that certain “traditional” reference genes are in fact regulated by LPS exposure, and, therefore, are not reliable candidates as their inclusion may compromise the accuracy of data interpretation. Testament to this, this study shows that the normalisation of gene expression data using an unstable reference gene greatly affects the experimental data obtained, and, therefore, the ultimate biological conclusions drawn.

Conclusion

This study reaffirms the importance of validating reference gene stability for individual experimental conditions. Given that gene expression levels in LPS stimulated macrophages is routinely used to infer biological phenomena that are of relevance to human conditions, verification of reference gene expression stability is crucial.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0223-y) contains supplementary material, which is available to authorized users.

Fragment-based drug discovery of potent and selective MKK3/6 inhibitors

The MAPK signaling cascade, comprised of several linear and intersecting pathways, propagates signaling into the nucleus resulting in cytokine and chemokine release. The Map Kinase Kinase isoforms 3 and 6 (MKK3 and MKK6) are responsible for the phosphorylation and activation of p38, and are hypothesized to play a key role in regulating this pathway without the redundancy seen in downstream effectors. Using FBDD, we have discovered efficient and selective inhibitors of MKK3 and MKK6 that can serve as tool molecules to help further understand the role of these kinases in MAPK signaling, and the potential impact of inhibiting kinases upstream of p38.

Protein-kinase inhibitors: A new treatment pathway for autoimmune and inflammatory diseases?

Although advances in biological medicine have seen significant progress in the treatment of autoimmune and inflammatory disease, many patients do not experience a satisfactory response. Hence, there are two challenges facing the medical research community. The first is to continue development in the field of existing biological therapies, such as monoclonal antibodies. The second is to open new frontiers of research and explore treatment alternatives for non-responders to other therapies. Attention has increasingly turned to the therapeutic potential of small molecule weight kinase inhibitors (SMKIs), currently used extensively in oncology and haematology. Initial research into the therapeutic value of SMKIs for autoimmune and inflammatory diseases has been encouraging. SMKIs are taken orally, which reduces cost for the health provider, and could increase compliance for the patient. This is why research is now focusing increasingly on SMKIs as a new generation line of treatment in these diseases. Tofacitinib, an inhibitor of Janus-kinase, is currently the only drug approved for the treatment of rheumatoid arthritis by FDA. However, much more needs to be done to understand the intracellular signalling pathways and how these might affect disease progression before solid conclusions can be drawn.