Organ-specific and differential requirement of TYK2 and IFNAR1 for LPS-induced iNOS expression in vivo

Type 1 interferon aggravates lipopolysaccharide-induced sepsis through upregulating Caspase-11 and Gasdermin D

This study aimed to investigate the mechanism of type I interferon (IFN) in aggravating sepsis in bacterial infection, focusing on the roles of Caspase-11 (Casp11) and Gasdermin D (Gsdmd) in this process. Type I interferons, including IFNα and IFNβ, were used to treat peritoneal macrophage harvested from wild-type or IFNα/βR1 knockout (KO) mice, of which the levels of Casp11 and Gsdmd were monitored using real-time polymerase chain reaction (RT-PCR) and Western blot, the exposure to phosphatidylserine was monitored by flow cytometry, and tissue factor (TF) activation was assessed by RT-PCR and TF chromogenic assay. Endotoxemia in wild-type mice led to upregulation of Casp11 and Gsdmd in myeloid cells, which in contrast was attenuated in IFNα/βR1 KO mice. IFNα or IFNβ treatment led to dose-dependent upregulation of Casp11 and Gsdmd in peritoneal macrophages harvested from wild-type mice, but induced negligible changes in IFNα/βR1 KO mice. Type I IFN promoted phosphatidylserine exposure in peritoneal macrophage from wild-type mice but not IFNα/βR1 KO mice. Type I IFN induced insignificant changes of TF expression levels in both wild-type mice and IFNα/βR1 KO mice, but the TF activity was markedly increased in wild-type mice after type I IFN treatment. Our data suggested that the upregulation of Casp11 and Gsdmd in myeloid cells and macrophages induced by endotoxemia was reliant on the expression of IFNα/βR1. IFNα or IFNβ treatment efficiently upregulated Casp11 and Gsdmd, phosphatidylserine exposure, and TF activity of macrophages. Therefore, type I IFN could aggravate sepsis through upregulating Casp11 and Gsdmd.

Evidence for an early innate immune response in the motor cortex of ALS

Background

Recent evidence indicates the importance of innate immunity and neuroinflammation with microgliosis in amyotrophic lateral sclerosis (ALS) pathology. The MCP1 (monocyte chemoattractant protein-1) and CCR2 (CC chemokine receptor 2) signaling system has been strongly associated with the innate immune responses observed in ALS patients, but the motor cortex has not been studied in detail.

Methods

After revealing the presence of MCP1 and CCR2 in the motor cortex of ALS patients, to elucidate, visualize, and define the timing, location and the extent of immune response in relation to upper motor neuron vulnerability and progressive degeneration in ALS, we developed MCP1-CCR2-hSOD1^G93A mice, an ALS reporter line, in which cells expressing MCP1 and CCR2 are genetically labeled by monomeric red fluorescent protein-1 and enhanced green fluorescent protein, respectively.

Results

In the motor cortex of MCP1-CCR2-hSOD1^G93A mice, unlike in the spinal cord, there was an early increase in the numbers of MCP1+ cells, which displayed microglial morphology and selectively expressed microglia markers. Even though fewer CCR2+ cells were present throughout the motor cortex, they were mainly infiltrating monocytes. Interestingly, MCP1+ cells were found in close proximity to the apical dendrites and cell bodies of corticospinal motor neurons (CSMN), further implicating the importance of their cellular interaction to neuronal pathology. Similar findings were observed in the motor cortex of ALS patients, where MCP1+ microglia were especially in close proximity to the degenerating apical dendrites of Betz cells.

Conclusions

Our findings reveal that the intricate cellular interplay between immune cells and upper motor neurons observed in the motor cortex of ALS mice is indeed recapitulated in ALS patients. We generated and characterized a novel model system, to study the cellular and molecular basis of this close cellular interaction and how that relates to motor neuron vulnerability and progressive degeneration in ALS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0896-4) contains supplementary material, which is available to authorized users.

Therapeutic potential of tyrosine kinase 2 in autoimmunity

INTRODUCTION

Tyrosine kinase 2 (Tyk2) is a Janus kinase family member that is crucial for signaling transduction in response to a wide variety of cytokines, including type I IFNs, IL-6, IL-10, IL-12 and IL-23. An appropriate expression of Tyk2-mediated signaling might be essential for maintaining normal immune responses.

AREAS COVERED

This review summarizes that Tyk2 is essential for the differentiation and function of a wide variety of immune cells, including natural killer cells, B cells, as well as T helper cells. In addition, Tyk2-mediated signaling promoted the production of autoimmune-associated components, which is implicated in the pathogenesis of autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis. Aberrant expression of Tyk2 was observed in many autoimmune conditions.

EXPERT OPINION

Until recently, no patent filings had claimed selective inhibitors of Tyk2. Both CP-690,500 and CMP6 failed to be used in clinical treatment due to the difficulties of finding suitable selective leads or due to detrimental toxicities. Although the result of Cmpd1 is promising, it remains to be seen how specific the Tyk2 inhibitor is and how they are working. Currently, structure-based drug design (SBDD) technology has provided us with a quite useful window for SBDD of Tyk2 inhibitors.

The interferons and their receptors--distribution and regulation

The interferons (IFNs) were originally described over 50 years ago, identified by their ability to confer viral resistance to cells. We now know that they are much more than just anti‐viral cytokines collectively having roles in both innate and adaptive immune responses, in tumor surveillance and defense, and modulation of immune cell function. Three types of IFN have now been described, simply referred to as type I, II and III. Distinguishable by the unique receptors that they rely on for signal transduction, the three types of IFN have specific and varied roles in the maintenance of human health and defense against pathogens. In mounting an IFN‐mediated immune response, the human body has developed the ability to regulate IFN‐mediated signal transduction. Like all cytokines, the ability of a cell to respond to IFN is completely dependent on the presence of its cognate receptor on the surface of the target cell. Thus, one of the major mechanisms used by the human body to regulate the strength and duration of the IFN response is through regulation of receptor levels, thereby altering the cytokine‐specific responsiveness of the target cell. This review will discuss the receptor system utilized by the type I IFNs and compare it with that of the type II and III IFNs, which also regulate immune responses through controlling receptor level on the cell surface.

The innate immune response recognises pathogens and sterile danger signals to generate effector cytokines, such as type I interferons (IFNs), with a high degree of sophistication. The May/June 2012 issue provides a series of reviews of the role of type I IFNs in regulating immune responses. Topics to be covered include the reason for the induction of IFNs, type I IFNs interactions with and regulation of target cells (e.g. T cells, B cells and Th10 cells) in the immune system, and the roles and mechanisms of IFNs in specific organs or diseases. The accompanying web focus presents links to related articles from across Nature Publishing Group to provide more background information about these proteins.

Strain specific transcriptional response in Mycobacterium tuberculosis infected macrophages

Background

Tuberculosis (TB), a bacterial infection caused by Mycobacterium tuberculosis (Mtb) remains a significant health problem worldwide with a third of the world population infected and nearly nine million new cases claiming 1.1 million deaths every year. The outcome following infection by Mtb is determined by a complex and dynamic host-pathogen interaction in which the phenotype of the pathogen and the immune status of the host play a role. However, the molecular mechanism by which Mtb strains induce different responses during intracellular infection of the host macrophage is not fully understood. To explore the early molecular events triggered upon Mtb infection of macrophages, we studied the transcriptional responses of murine bone marrow-derived macrophages (BMM) to infection with two clinical Mtb strains, CDC1551 and HN878. These strains have previously been shown to differ in their virulence/immunogenicity in the mouse and rabbit models of pulmonary TB.

Results

In spite of similar intracellular growth rates, we observed that compared to HN878, infection by CDC1551 of BMM was associated with an increased global transcriptome, up-regulation of a specific early (6 hours) immune response network and significantly elevated nitric oxide production. In contrast, at 24 hours post-infection of BMM by HN878, more host genes involved in lipid metabolism, including cholesterol metabolism and prostaglandin synthesis were up-regulated, compared to infection with CDC1551.

In association with the differences in the macrophage responses to infection with the 2 Mtb strains, intracellular CDC1551 expressed higher levels of stress response genes than did HN878.

Conclusions

In association with the early and more robust macrophage activation, intracellular CDC1551 cells were exposed to a higher level of stress leading to increased up-regulation of the bacterial stress response genes. In contrast, sub-optimal activation of macrophages and induction of a dysregulated host cell lipid metabolism favored a less stressful intracellular environment for HN878. Our findings suggest that the ability of CDC1551 and HN878 to differentially activate macrophages during infection probably determines their ability to either resist host cell immunity and progress to active disease or to succumb to the host protective responses and be driven into a non-replicating latent state in rabbit lungs.

Selective contribution of Tyk2 to cell activation by lipopolysaccharide

Tyk2 deficient mice show a markedly reduced susceptibility to lipopolysaccharide (LPS) induced shock and a partial impairment of IL-12 and interferon (IFN) signals. To examine the underlying mechanisms, we analysed the activation of peritoneal macrophages (PMPhis) and spleen cells after LPS challenge. In PMPhis and spleen cells the contribution of Tyk2 to the induction of the T-cell co-stimulatory molecules CD86, CD40 and MHC II was small or insignificant. By contrast, induced expression of the early activation marker CD69 on PMPhis and splenic cell populations required type I interferons (IFN-I) and Tyk2. The data suggest a selective contribution of Tyk2 to the activation of inflammation-relevant cell types by LPS.