CD40 Negatively Regulates ATP-TLR4-Activated Inflammasome in Microglia

Metabolite-derived damage-associated molecular patterns in immunological diseases

Damage-associated molecular patterns (DAMPs) are typically derived from the endogenous elements of necrosis cells and can trigger inflammatory responses by activating DAMPs-sensing receptors on immune cells. Failure to clear DAMPs may lead to persistent inflammation, thereby contributing to the pathogenesis of immunological diseases. This review focuses on a newly recognized class of DAMPs derived from lipid, glucose, nucleotide, and amino acid metabolic pathways, which are then termed as metabolite-derived DAMPs. This review summarizes the reported molecular mechanisms of these metabolite-derived DAMPs in exacerbating inflammation responses, which may attribute to the pathology of certain types of immunological diseases. Additionally, this review also highlights both direct and indirect clinical interventions that have been explored to mitigate the pathological effects of these DAMPs. By summarizing our current understanding of metabolite-derived DAMPs, this review aims to inspire future thoughts and endeavors on targeted medicinal interventions and the development of therapies for immunological diseases.

Aerobic glycolysis of bronchial epithelial cells rewires Mycoplasma pneumoniae pneumonia and promotes bacterial elimination

The immune response to Mycoplasma pneumoniae infection plays a key role in clinical symptoms. Previous investigations focused on the pro-inflammatory effects of leukocytes and the pivotal role of epithelial cell metabolic status in finely modulating the inflammatory response have been neglected. Herein, we examined how glycolysis in airway epithelial cells is affected by M. pneumoniae infection in an in vitro model. Additionally, we investigated the contribution of ATP to pulmonary inflammation. Metabolic analysis revealed a marked metabolic shift in bronchial epithelial cells during M. pneumoniae infection, characterized by increased glucose uptake, enhanced aerobic glycolysis, and augmented ATP synthesis. Notably, these metabolic alterations are orchestrated by adaptor proteins, MyD88 and TRAM. The resulting synthesized ATP is released into the extracellular milieu via vesicular exocytosis and pannexin protein channels, leading to a substantial increase in extracellular ATP levels. The conditioned medium supernatant from M. pneumoniae-infected epithelial cells enhances the secretion of both interleukin (IL)-1β and IL-18 by peripheral blood mononuclear cells, partially mediated by the P2X7 purine receptor (P2X7R). In vivo experiments confirm that addition of a conditioned medium exacerbates pulmonary inflammation, which can be attenuated by pre-treatment with a P2X7R inhibitor. Collectively, these findings highlight the significance of airway epithelial aerobic glycolysis in enhancing the pulmonary inflammatory response and aiding pathogen clearance.

Dexmedetomidine Alters the Inflammatory Profile of Rat Microglia In Vitro

BACKGROUND

Microglia are a primary mediator of the neuroinflammatory response to neurologic injury, such as that in traumatic brain injury. Their response includes changes to their cytokine expression, metabolic profile, and immunophenotype. Dexmedetomidine (DEX) is an α2 adrenergic agonist used as a sedative in critically ill patients, such as those with traumatic brain injury. Given its pharmacologic properties, DEX may alter the phenotype of inflammatory microglia.

METHODS

Primary microglia were isolated from Sprague-Dawley rats and cultured. Microglia were activated using multiple mediators: lipopolysaccharide (LPS), polyinosinic-polycytidylic acid (Poly I:C), and traumatic brain injury damage-associated molecular patterns (DAMP) from a rat that sustained a prior controlled cortical impact injury. After activation, cultures were treated with DEX. At the 24-h interval, the cell supernatant and cells were collected for the following studies: cytokine expression (tumor necrosis factor-α [TNFα], interleukin-10 [IL-10]) via enzyme-linked immunosorbent assay, 6-phosphofructokinase enzyme activity assay, and immunophenotype profiling with flow cytometry. Cytokine expression and metabolic enzyme activity data were analyzed using two-way analysis of variance. Cell surface marker expression was analyzed using FlowJo software.

RESULTS

In LPS-treated cultures, DEX treatment decreased the expression of TNFα from microglia (mean difference = 121.5 ± 15.96 pg/mL; p < 0.0001). Overall, DEX-treated cultures had a lower expression of IL-10 than nontreated cultures (mean difference = 39.33 ± 14.50 pg/mL, p < 0.0001). DEX decreased IL-10 expression in LPS-stimulated microglia (mean difference = 74.93 ± 12.50 pg/mL, p = 0.0039) and Poly I:C-stimulated microglia (mean difference = 23.27 ± 6.405 pg/mL, p = 0.0221). In DAMP-stimulated microglia, DEX decreased the activity of 6-phosphofructokinase (mean difference = 18.79 ± 6.508 units/mL; p = 0.0421). The microglial immunophenotype was altered to varying degrees with different inflammatory stimuli and DEX treatment.

CONCLUSIONS

DEX may alter the neuroinflammatory response of microglia. By altering the microglial profile, DEX may affect the progression of neurologic injury.

NLRP3 Inflammasome’s Activation in Acute and Chronic Brain Diseases—An Update on Pathogenetic Mechanisms and Therapeutic Perspectives with Respect to Other Inflammasomes

Increasingly prevalent acute and chronic human brain diseases are scourges for the elderly. Besides the lack of therapies, these ailments share a neuroinflammation that is triggered/sustained by different innate immunity-related protein oligomers called inflammasomes. Relevant neuroinflammation players such as microglia/monocytes typically exhibit a strong NLRP3 inflammasome activation. Hence the idea that NLRP3 suppression might solve neurodegenerative ailments. Here we review the recent Literature about this topic. First, we update conditions and mechanisms, including RNAs, extracellular vesicles/exosomes, endogenous compounds, and ethnic/pharmacological agents/extracts regulating NLRP3 function. Second, we pinpoint NLRP3-activating mechanisms and known NLRP3 inhibition effects in acute (ischemia, stroke, hemorrhage), chronic (Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, MS, ALS), and virus-induced (Zika, SARS-CoV-2, and others) human brain diseases. The available data show that (i) disease-specific divergent mechanisms activate the (mainly animal) brains NLRP3; (ii) no evidence proves that NLRP3 inhibition modifies human brain diseases (yet ad hoc trials are ongoing); and (iii) no findings exclude that concurrently activated other-than-NLRP3 inflammasomes might functionally replace the inhibited NLRP3. Finally, we highlight that among the causes of the persistent lack of therapies are the species difference problem in disease models and a preference for symptomatic over etiologic therapeutic approaches. Therefore, we posit that human neural cell-based disease models could drive etiological, pathogenetic, and therapeutic advances, including NLRP3’s and other inflammasomes’ regulation, while minimizing failure risks in candidate drug trials.

The Key Drivers of Brain Injury by Systemic Inflammatory Responses after Sepsis: Microglia and Neuroinflammation

Sepsis is a leading cause of intensive care unit admission and death worldwide. Most surviving patients show acute or chronic mental disorders, which are known as sepsis-associated encephalopathy (SAE). Although accumulating studies in the past two decades focused on the pathogenesis of SAE, a systematic review of retrospective studies which exclusively focuses on the inflammatory mechanisms of SAE has been lacking yet. This review summarizes the recent advance in the field of neuroinflammation and sheds light on the activation of microglia in SAE. Activation of microglia predominates neuroinflammation. As the gene expression profile changes, microglia show heterogeneous characterizations throughout all stages of SAE. Here, we summarize the systemic inflammation following sepsis and also the relationship of microglial diversity and neuroinflammation. Moreover, a collection of neuroinflammation-related dysfunction has also been reviewed to illustrate the possible mechanisms for SAE. In addition, promising pharmacological or non-pharmacological therapeutic strategies, especially those which target neuroinflammation or microglia, are also concluded in the final part of this review. Collectively, clarification of the vital relationship between neuroinflammation and SAE-related mental disorders would significantly improve our understanding of the pathophysiological mechanisms in SAE and therefore provide potential targets for therapies of SAE aimed at inhibiting neuroinflammation.

Implications of fractalkine on glial function, ablation and glial proteins/receptors/markers—understanding its therapeutic usefulness in neurological settings: a narrative review

Background

Fractalkine (CX3CL1) is a chemokine predominantly released by neurons. As a signaling molecule, CX3CL1 facilitates talk between neurons and glia. CX3CL1 is considered as a potential target which could alleviate neuroinflammation. However, certain controversial results and ambiguous role of CX3CL1 make it inexorable to decipher the overall effects of CX3CL1 on the physiopathology of glial cells.

Main body of the abstract

Implications of cross-talk between CX3CL1 and different glial proteins/receptors/markers will give a bird eye view of the therapeutic significance of CX3CL1. Keeping with the need, this review identifies the effects of CX3CL1 on glial physiopathology, glial ablation, and gives a wide coverage on the effects of CX3CL1 on certain glial proteins/receptors/markers.

Short conclusion

Pinpoint prediction of the therapeutic effect of CX3CL1 on neuroinflammation needs further research. This is owing to certain obscure roles and implications of CX3CL1 on different glial proteins/receptors/markers, which are crucial under neurological settings. Further challenges are imposed due to the dichotomous roles played by CX3CL1. The age-old chemokine shows many newer scopes of research in near future. Thus, overall assessment of the effect of CX3CL1 becomes crucial prior to its administration in neuroinflammation.

Mushroom Natural Products in Neurodegenerative Disease Drug Discovery

The variety of drugs available to treat neurodegenerative diseases is limited. Most of these drug's efficacy is restricted by individual genetics and disease stages and usually do not prevent neurodegeneration acting long after irreversible damage has already occurred. Thus, drugs targeting the molecular mechanisms underlying subsequent neurodegeneration have the potential to negate symptom manifestation and subsequent neurodegeneration. Neuroinflammation is a common feature of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis, and is associated with the activation of the NLRP3 inflammasome, which in turn leads to neurodegeneration. Inflammasome activation and oligomerisation is suggested to be a major driver of disease progression occurring in microglia. With several natural products and natural product derivatives currently in clinical trials, mushrooms have been highlighted as a rich and largely untapped source of biologically active compounds in both in vitro and in vivo neurodegenerative disease models, partially supported by successful clinical trial evaluations. Additionally, novel high-throughput methods for the screening of natural product compound libraries are being developed to help accelerate the neurodegenerative disease drug discovery process, targeting neuroinflammation. However, the breadth of research relating to mushroom natural product high-throughput screening is limited, providing an exciting opportunity for further detailed investigations.

Caspase-1 inhibition by YVAD generates tregs pivoting IL-17 to IL-22 response in β-glucan induced airway inflammation

BACKGROUND

During Aspergillus fumigatus mediated lung inflammation, NLRP3 inflammasome is rapidly activated that aggravates IL-1β production contributing to lung inflammation. Previously, we have shown the protective role of SYK-1 inhibition in inhibiting inflammasome activation during lung inflammation. In the current manuscript, we explored the protective role of direct caspase-1 inhibition during β-glucan-induced lung inflammation.

METHODS

We have mimicked the lung inflammation by administering intranasal β-glucan in mice model. YVAD was used for caspase-1 inhibition.

RESULTS

We have shown that caspase-1 inhibition by YVAD did not alter inflammasome independent inflammatory cytokines, while it significantly reduced inflammasome activation and IL-1β secretion. Caspase-1 inhibited bone marrow derived dendritic cells (BMDCs), co-cultured with T cells showed decreased T-cell proliferation and direct them to secrete high TGF-β and IL-10 compared to the T cells co-cultured with β-glucan primed dendritic cells. Caspase-1 inhibition in BMDCs also induced IL-22 secretion from CD4+T cells. Caspase-1 inhibition in intranasal β-glucan administered mice showed decreased tissue damage, immune cell infiltration and IgA secretion compared to control mice. Further, splenocytes challenged with β-glucan show high IL-10 secretion and increased FOXp3 and Ahr indicating an increase in regulatory T cells on caspase-1 inhibition.

CONCLUSION

Caspase-1 inhibition can thus be an attractive target to prevent inflammation mediated tissue damage during Aspergillus fumigatus mouse model and can be explored as an attractive therapeutic strategy.HIGHLIGHTSCaspase-1 inhibition protects lung damage from inflammation during β-glucan exposureCaspase-1 inhibition in dendritic cells decreases IL-1β production resulting in decreased pathogenic Th17Caspase-1 inhibition promotes regulatory T cells thereby inhibiting lung inflammation.

Insights into inflammasome regulation: cellular, molecular, and pathogenic control of inflammasome activation

Maintenance of immune homeostasis is an intricate process wherein inflammasomes play a pivotal role by contributing to innate and adaptive immune responses. Inflammasomes are ensembles of adaptor proteins that can trigger a signal following innate sensing of pathogens or non-pathogens eventuating in the inductions of IL-1β and IL-18. These inflammatory cytokines substantially influence the antigen-presenting cell's costimulatory functions and T helper cell differentiation, contributing to adaptive immunity. As acute and chronic disease conditions may accompany parallel tissue damage, we analyze the critical role of extracellular factors such as cytokines, amyloids, cholesterol crystals, etc., intracellular metabolites, and signaling molecules regulating inflammasome activation/inhibition. We develop an operative framework for inflammasome function and regulation by host cell factors and pathogens. While inflammasomes influence the innate and adaptive immune components' interplay modulating the anti-pathogen adaptive immune response, pathogens may target inflammasome inhibition as a survival strategy. As trapped between health and diseases, inflammasomes serve as promising therapeutic targets and their modus operandi serves as a scientific rationale for devising better therapeutic strategies.

Berberine mediates tumor cell death by skewing tumor-associated immunosuppressive macrophages to inflammatory macrophages

BACKGROUND

Berberine is a plant-derived alkaloid with potent anti-cancer activities. Berberine may redirect the tumor-promoting immunosuppressive M2 macrophages, to tumoricidal activated M1 macrophages. But such an anti-tumor function remains to be demonstrated.

HYPOTHESIS

Polarization of macrophages to an immunosuppressive phenotype within the tumor microenvironment promotes tumor growth and contributes to resistance to chemotherapy. We examined if berberine would target macrophage polarization to reinstate anti-tumor immune response.

STUDY DESIGN

Using a B16F10 mouse melanoma model, we assessed berberine-induced re-polarization of immunosuppressive M2 macrophages to anti-tumor M1 macrophages and subsequent T-cell activation within the immunosuppressive tumor microenvironment.

METHODS

The B16F10 culture supernatant along with tumor antigen was used as tumor mimicking conditioned medium (CM). The bone marrow-derived macrophages were cultured in CM for 5 days. The CM-induced skewing of macrophages to M2-like phenotype was confirmed by flow cytometry and ELISA. The T-cells were co-cultured with macrophages to decipher the effect of berberine on T-cell differentiation. In vivo efficacy of berberine was analyzed using melanoma model of solid tumor.

RESULTS

Berberine inhibited rIL-6-induced STAT-3 phosphorylation and IL-10 release from B16F10 cells. It enhanced tumor antigen-induced IL-1β, IL-12 and TNFα, but suppressed IL-6 and TGF-β release. Berberine significantly prevented the tumor antigen-mediated IL-10-enhanced IL-6 and TGF-β expression. The CM skewed the bone marrow-derived macrophages to CD206-high but MHC-II-low M2-like tumor-associated macrophages. Berberine partially prevented the generation of these macrophages and was associated with reduced C/EBPβ and Egr2 mRNA expression and lowered IL-10 and TGF-β production. Berberine significantly reduced Arginase-1 expression in CM-treated M1 and M2-like macrophages. Berberine increased MHC-II and CD40 expression on the macrophages augmenting the CTL activity and the number of IFNγ-producing CD4+ T-cells. Berberine significantly lowered tumor volume, weight and enhanced the frequency of M1-like macrophages in mice.

CONCLUSION

These data indicate that berberine interferes with pro-tumor macrophage polarization and IL-10 and TGF-β release but restores Tcell anti-tumor cytotoxicity in the tumor microenvironment.

The Signaling Pathways Regulating NLRP3 Inflammasome Activation

The NLRP3 inflammasome is a multi-molecular complex that acts as a molecular platform to mediate caspase-1 activation, leading to IL-1β/IL-18 maturation and release in cells stimulated by various pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs). This inflammasome plays an important role in the innate immunity as its activation can further promote the occurrence of inflammation, enhance the ability of host to remove pathogens, and thus facilitate the repair of injured tissues. But if the inflammasome activation is dysregulated, it will cause the development of various inflammatory diseases and metabolic disorders. Therefore, under normal conditions, the activation of inflammasome is tightly regulated by various positive and negative signaling pathways to respond to the stimuli without damaging the host itself while maintaining homeostasis. In this review, we summarize recent advances in the major signaling pathways (including TLRs, MAPK, mTOR, autophagy, PKA, AMPK, and IFNR) that regulate NLRP3 inflammasome activation, providing a brief view of the molecular network that regulates this inflammasome as a theoretical basis for therapeutic intervention of NLRP3 dysregulation-related diseases.

Toll-like receptor 4 is activated by platinum and contributes to cisplatin-induced ototoxicity

Toll-like receptor 4 (TLR4) recognizes bacterial lipopolysaccharide (LPS) and can also be activated by some Group 9/10 transition metals, which is believed to mediate immune hypersensitivity reactions. In this work, we test whether TLR4 can be activated by the Group 10 metal platinum and the platinum-based chemotherapeutic cisplatin. Cisplatin is invaluable in childhood cancer treatment but its use is limited due to a permanent hearing loss (cisplatin-induced ototoxicity, CIO) adverse effect. We demonstrate that platinum and cisplatin activate pathways downstream of TLR4 to a similar extent as the known TLR4 agonists LPS and nickel. We further show that TLR4 is required for cisplatin-induced inflammatory, oxidative, and cell death responses in hair cells in vitro and for hair cell damage in vivo. Finally, we identify a TLR4 small molecule inhibitor able to curtail cisplatin toxicity in vitro. Thus, our findings indicate that TLR4 is a promising therapeutic target to mitigate CIO.

microRNAs (miR 9, 124, 155 and 224) transdifferentiate mouse macrophages to neurons

Development is an irreversible process of differentiating the undifferentiated cells to functional cells. Brain development involves generation of cells with varied phenotype and functions, which is limited during adulthood, stress, damage/degeneration. Cellular reprogramming makes differentiation reversible process with reprogramming somatic/stem cells to alternative fate with/without stem cells. Exogenously expressed transcription factors or small molecule inhibitors have driven reprogramming of stem/somatic cells to neurons providing alternative approach for pre-clinical/clinical testing and therapeutics. Here in, we report a novel approach of microRNA (miR)- induced trans-differentiation of macrophages (CD11b high) to induced neuronal cells (iNCs) (neuronal markershigh- Nestin, Nurr1, Map2, NSE, Tubb3 and Mash1) without exogenous use of transcription factors. miR 9, 124, 155 and 224 successfully transdifferentiated macrophages to neurons with transient stem cell-like phenotype. We report trans differentiation efficacy 18% and 21% with miR 124 and miR 155. in silico(String 10.0, miR gator, mESAdb, TargetScan 7.0) and experimental analysis indicate that the reprogramming involves alteration of pluripotencygenes like Oct4, Sox2, Klf4, Nanog and pluripotency miR, miR 302. iNCs also shifted to G0 phase indicating manipulation of cell cycle by these miRs. Further, CD133+ intermediate cells obtained during current protocol could be differentiated to iNCs using miRs. The syanpsin⁺ neurons were functionally active and displayed intracellular Ca⁺² evoke on activation. miRs could also transdifferentiate bone marrow-derived macrophages and peripheral blood mononuclear cells to neuronal cells. The current protocol could be employed for direct in vivo reprogramming of macrophages to neurons without teratoma formation for transplantation and clinical studies.

Manipulation of Inflammasome: A Promising Approach Towards Immunotherapy of Lung Cancer

Chronic inflammation has emerged as a key player at different stages of cancer development. A prominent signaling pathway for acute and chronic inflammation is the activation of the caspase-1 inflammasomes. These are complexes that assemble on activation of certain nucleotide-binding domain, leucine-rich repeat containing proteins (NLRs), AIM2-like receptors (ALRs), or pyrin due to activation via PAMPs or DAMPs. Of these, five complexes-NLRP1, NLRP3, NLRC4, Pyrin, and AIM2 are of importance in the context of cancer for their activities in modulating immune responses, cell proliferation, and apoptosis. Inflammasomes have emerged as clinically relevant in multiple forms of cancer making them highly promising targets for cancer therapy. As lungs are a tissue niche that is prone to inflammation owing to its exposure to external substances, inflammasomes play a vital role in the development and pathogenesis of lung cancer. Therefore, manipulation of inflammasome by various immunomodulatory means could prove a full-proof strategy for the treatment of lung cancer. Here, in this review, we tried to explore the various strategies to target the inflammasomes for the treatment of lung cancer.

Regulation of neuroimmune processes by damage- and resolution-associated molecular patterns

Sterile inflammatory processes are essential for the maintenance of central nervous system homeostasis, but they also contribute to various neurological disorders, including neurotrauma, stroke, and demyelinating or neurodegenerative diseases. Immune mechanisms in the central nervous system and periphery are regulated by a diverse group of endogenous proteins, which can be broadly divided into the pro-inflammatory damage-associated molecular patterns (DAMPs) and anti-inflammatory resolution-associated molecular patterns (RAMPs), even though there is notable overlap between the DAMP- and RAMP-like activities for some of these molecules. Both groups of molecular patterns were initially described in peripheral immune processes and pathologies; however, it is now evident that at least some, if not all, of these immunomodulators also regulate neuroimmune processes and contribute to neuroinflammation in diverse central nervous system disorders. The review of recent literature demonstrates that studies on DAMPs and RAMPs of the central nervous system still lag behind the much broader research effort focused on their peripheral counterparts. Nevertheless, this review also reveals that over the last five years, significant advances have been made in our understanding of the neuroimmune functions of several well-established DAMPs, including high-mobility group box 1 protein and interleukin 33. Novel neuroimmune functions have been demonstrated for other DAMPs that previously were considered almost exclusively as peripheral immune regulators; they include mitochondrial transcription factor A and cytochrome C. RAMPs of the central nervous system are an emerging area of neuroimmunology with very high translational potential since some of these molecules have already been used in preclinical and clinical studies as candidate therapeutic agents for inflammatory conditions, such as multiple sclerosis and rheumatoid arthritis. The therapeutic potential of DAMP antagonists and neutralizing antibodies in central nervous system neuroinflammatory diseases is also supported by several of the identified studies. It can be concluded that further studies of DAMPs and RAMPs of the central nervous system will continue to be an important and productive field of neuroimmunology.

Purinergic System Signaling in Metainflammation-Associated Osteoarthritis

Inflammation triggered by metabolic imbalance, also called metainflammation, is low-grade inflammation caused by the components involved in metabolic syndrome (MetS), including central obesity and impaired glucose tolerance. This phenomenon is mainly due to excess nutrients and energy, and it contributes to the pathogenesis of osteoarthritis (OA). OA is characterized by the progressive degeneration of articular cartilage, which suffers erosion and progressively becomes thinner. Purinergic signaling is involved in several physiological and pathological processes, such as cell proliferation in development and tissue regeneration, neurotransmission and inflammation. Adenosine and ATP receptors, and other members of the signaling pathway, such as AMP-activated protein kinase (AMPK), are involved in obesity, type 2 diabetes (T2D) and OA progression. In this review, we focus on purinergic regulation in osteoarthritic cartilage and how different components of MetS, such as obesity and T2D, modulate the purinergic system in OA. In that regard, we describe the critical role in this disease of receptors, such as adenosine A2A receptor (A2AR) and ATP P2X7 receptor. Finally, we also assess how nucleotides regulate the inflammasome in OA.

Overview of General and Discriminating Markers of Differential Microglia Phenotypes

Inflammatory processes and microglia activation accompany most of the pathophysiological diseases in the central nervous system. It is proven that glial pathology precedes and even drives the development of multiple neurodegenerative conditions. A growing number of studies point out the importance of microglia in brain development as well as in physiological functioning. These resident brain immune cells are divergent from the peripherally infiltrated macrophages, but their precise in situ discrimination is surprisingly difficult. Microglial heterogeneity in the brain is especially visible in their morphology and cell density in particular brain structures but also in the expression of cellular markers. This often determines their role in physiology or pathology of brain functioning. The species differences between rodent and human markers add complexity to the whole picture. Furthermore, due to activation, microglia show a broad spectrum of phenotypes ranging from the pro-inflammatory, potentially cytotoxic M1 to the anti-inflammatory, scavenging, and regenerative M2. A precise distinction of specific phenotypes is nowadays essential to study microglial functions and tissue state in such a quickly changing environment. Due to the overwhelming amount of data on multiple sets of markers that is available for such studies, the choice of appropriate markers is a scientific challenge. This review gathers, classifies, and describes known and recently discovered protein markers expressed by microglial cells in their different phenotypes. The presented microglia markers include qualitative and semi-quantitative, general and specific, surface and intracellular proteins, as well as secreted molecules. The information provided here creates a comprehensive and practical guide through the current knowledge and will facilitate the choosing of proper, more specific markers for detailed studies on microglia and neuroinflammatory mechanisms in various physiological as well as pathological conditions. Both basic research and clinical medicine need clearly described and validated molecular markers of microglia phenotype, which are essential in diagnostics, treatment, and prevention of diseases engaging glia activation.

Autophagy and inflammation in ischemic stroke

Appropriate autophagy has protective effects on ischemic nerve tissue, while excessive autophagy may cause cell death. The inflammatory response plays an important role in the survival of nerve cells and the recovery of neural tissue after ischemia. Many studies have found an interaction between autophagy and inflammation in the pathogenesis of ischemic stroke. This study outlines recent advances regarding the role of autophagy in the post-stroke inflammatory response as follows. (1) Autophagy inhibits inflammatory responses caused by ischemic stimulation through mTOR, the AMPK pathway, and inhibition of inflammasome activation. (2) Activation of inflammation triggers the formation of autophagosomes, and the upregulation of autophagy levels is marked by a significant increase in the autophagy-forming markers LC3-II and Beclin-1. Lipopolysaccharide stimulates microglia and inhibits ULK1 activity by direct phosphorylation of p38 MAPK, reducing the flux and autophagy level, thereby inducing inflammatory activity. (3) By blocking the activation of autophagy, the activation of inflammasomes can alleviate cerebral ischemic injury. Autophagy can also regulate the phenotypic alternation of microglia through the nuclear factor-κB pathway, which is beneficial to the recovery of neural tissue after ischemia. Studies have shown that some drugs such as resveratrol can exert neuroprotective effects by regulating the autophagy-inflammatory pathway. These studies suggest that the autophagy-inflammatory pathway may provide a new direction for the treatment of ischemic stroke.

Connexins-Based Hemichannels/Channels and Their Relationship with Inflammation, Seizures and Epilepsy

Connexins (Cxs) are a family of 21 protein isoforms, eleven of which are expressed in the central nervous system, and they are found in neurons and glia. Cxs form hemichannels (connexons) and channels (gap junctions/electric synapses) that permit functional and metabolic coupling between neurons and astrocytes. Altered Cx expression and function is involved in inflammation and neurological diseases. Cxs-based hemichannels and channels have a relevance to seizures and epilepsy in two ways: First, this pathological condition increases the opening probability of hemichannels in glial cells to enable gliotransmitter release, sustaining the inflammatory process and exacerbating seizure generation and epileptogenesis, and second, the opening of channels favors excitability and synchronization through coupled neurons. These biological events highlight the global pathological mechanism of epilepsy, and the therapeutic potential of Cxs-based hemichannels and channels. Therefore, this review describes the role of Cxs in neuroinflammation and epilepsy and examines how the blocking of channels and hemichannels may be therapeutic targets of anti-convulsive and anti-epileptic treatments.

Experimental listeriosis: A study of purinergic and cholinergic inflammatory pathway

The cholinergic, purinergic and oxidative stress systems were related to nervous system damage in some pathologies, as well as being involved in pro-inflammatory and anti-inflammatory pathways. The objective was to investigate changes in purinergic, cholinergic systems and oxidative stress related to the neuropathology of listeriosis. Gerbils were used as experimental models. The animals were divided in two groups: control and infected. The animals were orally infected with 5 × 10⁸ CFU/animal of the pathogenic strain of Listeria monocytogenes. Collected of material was 6 and 12th days post-infection (PI). Infected animals showed moderate mixed inflammatory infiltrates in the liver. The spleen and brain was used for PCR analyses, confirming infection by L. monocytogenes. Increase in number of total leukocytes because of an increase in lymphocytes in infected (P < 0.001). ATP and ADP hydrolysis by NTPDase was lower at 6 and 12th days PI in infected animals than in the control group. ADA (adenosine deaminase) activity was higher on the 6th day PI (P < 0.05) and decreased on the 12th day PI (P < 0.05) in infected animals. AChE (acetylcholinesterase) activity did not differ between groups on the 6th day PI; however, activity decreased in infected group on the 12th day PI (P < 0.05). On the 12th day PI, an increase of oxygen-reactive species levels and lower catalase and superoxide dismutase activities in the infected group was observed, characterizing a situation of cerebral oxidative stress. The inflammatory and oxidative mechanisms are present in listeriosis in asymptomatic animals, and that ectonucleotidases and cholinesterase's are involved in immunomodulation.

Safety and Clinical Efficacy of Yangxue Qingnao Granules in the Treatment of Chronic Cerebral Circulation Insufficiency: A Systematic Review and Meta-Analysis

To evaluate the safety and clinical efficacy of Yangxue Qingnao (YXQN) granules in the treatment of chronic cerebral circulation insufficiency (CCCI), electronic databases—PubMed, Embase, CNKI, VIP, and Wangfang—were searched for randomized controlled trials (RCTs) published up to January 2019. GRADE and RevMan 5.3.0 were used for grading and analysis, respectively. Fifteen trials involving 1211 CCCI patients were included. Subgroup analysis was performed owing to study heterogeneity. Compared to nimodipine plus routine treatment, YXQN granules plus routine treatment were more effective in increasing basilar artery (BA) blood flow velocity (mean difference (MD) = 3.34, 95% confidence interval (CI) = [2.31, 4.37], P < 0.00001), vertebral artery (VA) blood flow velocity (MD = 0.52, 95% CI = [0.27, 0.76], P < 0.0001), and internal carotid artery (ICA) blood flow velocity (MD = 7.46, 95% CI = [2.01, 12.90], P=0.007). In improving the clinical efficacy of traditional Chinese medicine (TCM) for symptoms such as headache, dizziness, and insomnia, YXQN granules plus routine treatment were shown to be superior to the following control treatments: nimodipine plus routine treatment (mean difference (M-H) = 4.21, 95% CI = [2.49, 7.12], P < 0.00001), flunarizine plus routine treatment (mean difference (M-H) = 3.92, 95% CI = [1.36, 11.29], P=0.01), troxerutin plus routine treatment (mean difference (M-H) = 4.79, 95% CI = [2.20, 10.42], P < 0.00001), and routine treatment (mean difference (M-H) = 6.13, 95% CI = [1.48, 25.34], P=0.01). Risk of bias was assessed in 15 trials. One analysis was graded using GRADE and showed poor results. Adverse events were not reported explicitly in all but one trial. Thus, this meta-analysis suggests that YXQN granules may be beneficial for patients with CCCI. However, owing to the poor quality of the clinical trials and small sample sizes, a definite conclusion on the efficacy and safety of YXQN granules cannot be drawn from existing information.

Insights into inflammasome and its research advances in cancer

Inflammation has long been proven to engage in tumor initiation and progression. Inflammasome, as a member of innate immunity-induced host defense inflammation, also plays critical roles in cancer. Inflammasome is a multiprotein complex responding to pathogen-associated molecular patterns and damage-associated molecular patterns. It is composed of receptors such as NOD-like receptors and AIM2-like receptors, adaptor protein ASC, and effector caspase-1, which can process proinflammatory cytokines interleukin (IL)-1β and IL-18. It has been reported that upregulated inflammasome activity is correlated to various types of cancers including breast cancer, gastric cancer, brain tumor, and malignant prostate, while inflammasomes also have a protective role in colitis-associated cancer. Autophagy, an intracellular recycling process for maintaining homeostasis, is deemed to contribute to the underlying mechanism of its dual roles in cancer. It has been found that distinct tumor stages and different isotypes of caspases involved in the inflammasome pathway can affect the roles of inflammasome in cancer. In this review, we update the latest evidence of inflammasome roles in cancer and novel inflammasome pathway-targeting agents for immunotherapy and discuss future research directions of inflammasome-based target therapy.

Activation of Nicotinic Acetylcholine α7 Receptor Attenuates Progression of Monocrotaline-Induced Pulmonary Hypertension in Rats by Downregulating the NLRP3 Inflammasome

Background: Inflammation and altered immunity contribute to the development of pulmonary arterial hypertension (PH). The alpha 7 nicotinic acetylcholine receptor (α7nAChR) possesses anti-inflammatory activities. The current study was performed to investigate the effects of a selective α7nAChR agonist, PNU-282987, on controlling a monocrotaline (MCT)-induced rat model of PH and explored the underlying mechanisms.

Methods: Sprague-Dawley rats were injected with MCT and treated with PNU-282987 at the prevention (starting 1 week before MCT) and treatment (starting 2 weeks after MCT) settings. Four weeks after MCT injection, hemodynamic changes, right ventricular structure, and lung morphological features were assessed. Enzyme-linked immunosorbent assay, Western blot and qRT-PCR were performed to assess levels of inflammatory cytokines and NLRP3 (Nod-like receptor family pyrin domain-containing 3) inflammasome pathway in the rat lung tissues. In addition, the lung macrophage line NR8383 was used to confirm the in vivo data.

Results: Monocrotaline injection produced PH in rats and downregulated α7nAChR mRNA and protein expression in rat lung tissues compared to sham controls. Pharmacological activation of α7nAChR by PNU-282987 therapy improved the rat survival rate, attenuated the development of PH as assessed by remodeling of pulmonary arterioles, reduced the right ventricular (RV) systolic pressure, and ameliorated the hypertrophy and fibrosis of the RV in rats with MCT-induced PH. The expression of TNF-α, IL-6, IL-1β, and IL-18 were downregulated in rat lung tissues, which implied that PNU-282987 therapy may help regulate inflammation. These protective effects involved the inhibition of the NLRP3 inflammasome. In vitro assays of cultured rat lung macrophages confirmed that the anti-inflammation effect of PNU-282987 therapy may contribute to the disturbance of NLRP3 inflammasome activation.

Conclusion: Targeting α7nAChR with PNU-282987 could effectively prevent and treat PH with benefits for preventing ongoing inflammation in the lungs of rats with MCT-induced PH by inhibiting NLRP3 inflammasome activation.

Dexmedetomidine inhibits inflammation in microglia cells under stimulation of LPS and ATP by c-Fos/NLRP3/caspase-1 cascades

NOD-like receptor 3 (NLRP3) plays critical roles in the initiation of inflammasome-mediated inflammation in microglia, thus becomes an important therapeutic target of Alzheimer's disease (AD). Dexmedetomidine (Dex), a new type of clinical anesthetic agent, shows anti-inflammatory properties and inhibits postoperative cognitive dysfunction in AD patients. The present study was aimed to investigate effect of Dex on NLRP3 activity in activated microglia and reveal the underlying mechanisms. The human microglia clone 3 (HMC3) cells were exposed to 100 ng/ml LPS and 5 mM ATP, in the presence and absence of doses of Dex. Data from ELISA and Western blot assays showed that Dex abrogated the promoting effects of LPS/ATP on the release of pro-inflammatory cytokines including IL-1β and IL-18 in the cell medium and the expression of NLRP3 and its downstream target caspase-1 in HMC3 cells. Furthermore, the present study found that exposure of HMC3 cells to LPS/ATP increased nuclear protein levels of transcription factor c-Fos, but treatment with Dex reversed the increase in c-Fos, as indicated by Western blot and immunofluorescence measures. Luciferase reported assay revealed that c-Fos can bind to the promoter region of NLRP3 gene and positively regulate the expression. These results suggest that Dex inhibiting c-Fos nuclear protein levels promoted by LPS/ATP blocks the up-regulation of NLRP3. This suggestion is supported by co-immunoprecipitation and PCR studies, in which Dex decreased the amount of c-Fos that binds to NLRP3 under the stimulation of LPS/ATP. The present study revealed that Dex inhibits inflammation in microglia cells under stimulation of LPS and ATP by c-Fos/NLRP3/caspase-1 cascades, which adds new understanding of the anti-inflammatory mechanism of Dex.

Salmeterol, agonist of β2-aderenergic receptor, prevents systemic inflammation via inhibiting NLRP3 inflammasome

β2-Aderenergic receptor (β2AR) agonist, Salmeterol exhibits anti-inflammatory activities. However, the inhibitory effects of Salmeterol on inflammasome activation are elusive and the underlying mechanisms need to be explored. In this study, we established inflammatory model in primary bone marrow-derived macrophages (BMDM) from C57BL/6J mice and β-arrestin2 knockout (β-arrestin2^-/-) mice in vitro. In vivo study by LPS intraperitoneally (i.p.) in C57BL/6J mice was carried out to ascertain its roles in systemic inflammation. We found that Salmeterol (10^-10 M-10^-7 M) prevented the cleavage of caspase-1 and the activation of NLRP3 inflammasome, reduced the release of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in vitro. Blockade of adenosine3',5'cyclic monophosphate (cAMP)/protein kinase A (PKA) pathway with cAMP or PKA inhibitors inhibited anti-inflammatory effects of Salmeterol only at 10^-7 M. Depletion of β-arrestin2 compromised the inhibitory effects of Salmeterol at both 10^-10 M and 10^-7 M. Salmeterol increased the interaction of β-arrestin2 and NLRP3. In vivo study showed that Salmeterol decreased the serum concentrations of pro-inflammatory cytokines IL-1β and TNF-α, blocked cleavage of caspase-1 and release of IL-1β in BMDM. These findings imply that Salmeterol at low concentrations (10^-10 M-10^-7 M) shows anti-inflammatory effect via inhibiting NLRP3 inflammasome. The underlying mechanisms is dosage-dependent: Salmeterol at 10^-10 M shows anti-inflammatory effects through β-arrestin2 pathway, and 10^-7 M Salmeterol inhibits inflammation via both classical G-protein coupled receptor (GPCR)/cAMP pathway and β-arrestin2 pathway. These results provide new ideas for the future treatment of systemic inflammation and other inflammatory diseases.

Microglia Polarization with M1/M2 Phenotype Changes in rd1 Mouse Model of Retinal Degeneration

Microglia activation is recognized as the hallmark of neuroinflammation. However, the activation profile and phenotype changes of microglia during the process of retinal degeneration are poorly understood. This study aimed to elucidate the time-spatial pattern of microglia distribution and characterize the polarized phenotype of activated microglia during retinal neuroinflammation and degeneration in rd1 (Pde6β^rd1/rd1) mice, the classic model of inherited retinal degeneration. Retinae of rd1 mice at different postnatal days (P7, P14, P21, P28, P56, and P180) were prepared for further analysis. We found most CD11b⁺ or IBA1⁺ microglia expressed Ki-67 and CD68 in rd1 mice and these cells migrated toward the layer of degenerative photoreceptors at the rapid rods degeneration phase from P14 to P28. These microglia exhibited typical ameboid activated shape with round bodies and scarce dendrites, while at late phase at P180, they displayed resting ramified morphology with elongated dendrites. Flow cytometry revealed that the percentage of CD86⁺CD206^- M1 microglia increased markedly in rd1 retinae, however, no significant change was observed in CD206⁺CD86^- M2 microglia. Interestingly, CD86⁺CD206⁺ microglia, an intermediate state between the two extremes of M1 and M2, increased markedly at the rapid rods degeneration phase. The immunofluorescence images revealed that microglia in rd1 mice highly expressed M1 markers including CD16/32, CD86, and CD40. In addition, increased expression of pro-inflammatory cytokines (TNF-α, IL-6, and CCL2) was observed in rd1 mice. Our findings unfolded a panorama for the first time that microglia conducted distinctive behaviors with the progression of retinal degeneration in rd1 mice. Microglia is activated and particularly polarized to a pro-inflammatory M1 phenotype at the rapid rods degenerative phase, suggesting that the involvement of M1 microglia in the retinal neuroinflammation and degeneration. Most microglia adopted an intermediate polarization “M1½” state in rd1, revealing that microglia orchestrated a complicated continuous spectrum in degenerative retina.

Negative regulators and their mechanisms in NLRP3 inflammasome activation and signaling

Inflammasomes are cytosolic multiprotein complexes that cause the release of biologically active interleukin-1β. The best-characterized inflammasome is the NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 or Nod-like receptor protein 3) inflammasome. The NLRP3 inflammasome forms an assembly consisting of the ASC (apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain) adaptor protein and the effector, caspase-1 (cysteine-dependent aspartate-directed protease-1). Numerous agents and ligands derived from pathogens, modified self-cells and the environment induce NLRP3 inflammasome complex formation. NLRP3 inflammasome activation is tightly controlled at the transcriptional and post-translational levels to prevent unwanted excessive inflammation. Recent studies have highlighted the roles and mechanisms of several negative regulators that inhibit the assembly of NLRP3 inflammasome complexes and suppress inflammatory responses. The identification and characterization of new players in the regulation of NLRP3 inflammasome may lead to the development of inflammasome-targeting therapeutics against various inflammatory diseases related to NLRP3 inflammasome-associated pathogenesis.