Author response: IL-37 expression reduces acute and chronic neuroinflammation and rescues cognitive impairment in an Alzheimer’s disease mouse model (2022)

Article Figures and data Abstract Editor's evaluation Introduction Results Discussion Materials and methods Data availability References Decision letter Author response Article and author information Metrics Abstract The anti-inflammatory cytokine interleukin-37 (IL-37) belongs to the IL-1 family but is not expressed in mice. We used a human IL-37 (hIL-37tg) expressing mouse, which has been subjected to various models of local and systemic inflammation as well as immunological challenges. Previous studies reveal an immunomodulatory role of IL-37, which can be characterized as an important suppressor of innate immunity. Here, we examined the functions of IL-37 in the central nervous system and explored the effects of IL-37 on neuronal architecture and function, microglial phenotype, cytokine production and behavior after inflammatory challenge by intraperitoneal LPS-injection. In wild-type mice, decreased spine density, activated microglial phenotype and impaired long-term potentiation (LTP) were observed after LPS injection, whereas hIL-37tg mice showed no impairment. In addition, we crossed the hIL-37tg mouse with an animal model of Alzheimer's disease (APP/PS1) to investigate the anti-inflammatory properties of IL-37 under chronic neuroinflammatory conditions. Our results show that expression of IL-37 is able to limit inflammation in the brain after acute inflammatory events and prevent loss of cognitive abilities in a mouse model of AD. Editor's evaluation In this manuscript, the authors demonstrated that acute and chronic neuroinflammation was attenuated in human IL-37 (hIL-37) transgenic mice, thus revealing the effects of an anti-inflammatory cytokine hIL-37 in the central nervous system of mice. This study will be of interest to scientists studying neuroinflammation and searching for potential therapeutic targets. https://doi.org/10.7554/eLife.75889.sa0 Decision letter Reviews on Sciety eLife's review process Introduction Neuroinflammation is characterized by glial cell activation and is mediated via pro-inflammatory signals (Ji et al., 2014; Rivest, 2009). In general, acute inflammation is the initial response of the immune system and is characterized by activation of immune cells, rapid production of various cytokines and chemokines, and phagocytic mechanisms. Although these processes are important to combat pathogens, persistent inflammation can lead to a pathophysiological state that results in tissue damage and loss of function. It is well known that during inflammation, pro- and anti-inflammatory cytokines interact and influence the outcome. Examples of pro-inflammatory cytokines include interleukin (IL)–1β and tumor necrosis factor α (TNF-α), both of which elicit a strong acute inflammatory response (Dinarello, 1996; Leal et al., 2013). In contrast, anti-inflammatory cytokines such as IL-4, IL-10 (De Beaux et al., 1996; Marie et al., 1996), or IL-37 (Nold et al., 2010) inhibit the action of pro-inflammatory cytokines and hence limit inflammation (Cavaillon, 2001). In the CNS, long-term activation of glial cells leads to neuroinflammation, which is an important hallmark of many neurological disorders, including Alzheimer's disease (AD), Parkinson's disease or multiple sclerosis (Ji et al., 2014). In particular, AD is the most common form of dementia characterized by amyloid-β plaques and neurofibrillary tangles in the brain tissue. Patients with AD suffer from memory loss, speech disorders, confusion, problems with attention, and spatial orientation. Currently, there are no effective treatment strategies to combat AD despite the considerable clinical need. Innate immune responses and neuroinflammation are thought to contribute significantly to the progression of AD (Tan et al., 2007). Therefore, regulatory cytokines that can reduce inflammation in the CNS are of therapeutic value (Banchereau et al., 2012; Cavalli et al., 2016). Nevertheless, it remains unclear which of the regulatory mediators act adversely or beneficially at each stage of the neuroinflammatory process (Ji et al., 2014; Grace et al., 2014; Kigerl et al., 2009). For example, the release of IL-1β under pathological conditions can lead to deficits in learning and memory processes as well as in long-term potentiation (LTP) (Avital et al., 2003; Hein et al., 2010; Tong et al., 2012). In addition, pro-inflammatory cytokines such as TNF-α and interferon-γ (IFN-γ) have been associated with impairments in hippocampal neuron structure and function during viral infection (Hosseini et al., 2018). It is important to note that in chronic inflammation, the homeostasis of pro- and anti-inflammatory mediators is completely disturbed and must be therapeutically directed at attenuating persistent inflammatory processes. Among the important pro-inflammatory mediators, both IL-1α and IL-1β play a role in autoinflammatory, autoimmune, infectious, and degenerative diseases (Dinarello, 2009; Dinarello, 2010; Dinarello et al., 2012; Gabay et al., 2010; Sims and Smith, 2010). Although IL-1α and IL-1β are encoded by different genes, both cytokines are structurally related proteins that bind to the type I interleukin 1 receptor (IL-1R1) and elicit similar innate responses. However, IL-1α is constitutively present in healthy cells but is only released under cell stress conditions, as is the case during inflammation. Moreover, because it is constitutively present, IL-1α acts rapidly to trigger local inflammation. In contrast, IL-1β is not present in the healthy state; the IL-1β precursor is not active but requires processing by caspase-1, an intracellular protease, resulting in conversion to an active cytokine that is secreted (Garlanda et al., 2013). Unlike most members of the IL-1 family that induce inflammation, this important cytokine family also includes two members (IL-37 and IL-38) that act as anti-inflammatory signalling agents and are thought to dampen an ongoing innate immune response (Nold et al., 2010; Dinarello, 2018). In particularly, IL-37 serves as a potent mediator to limit the inflammatory responses (Cavalli and Dinarello, 2018; Caraffa et al., 2018). Therefore, a transgenic mouse model expressing the human splice variant IL-37b (hIL-37tg) was developed (Nold et al., 2010; Cavalli and Dinarello, 2018) and showed potent anti-inflammatory and beneficial effects in a wide variety of different pathological conditions in different organs (Nold et al., 2010; Ballak et al., 2014; Coll-Miró et al., 2016; McNamee et al., 2011; Yousif et al., 2011). The transgenic mouse was generated to allow continuous expression of IL-37 in almost all cells. This was achieved by using the full-length cDNA of IL-37b through the CMV promoter (Nold et al., 2010). It is important to note that these IL-37tg mice did not exhibit an abnormal phenotype and reproduced normally (Nold et al., 2010; Dinarello et al., 2016). IL-37 has been described as a protein that binds to the IL-18 receptor (IL-18R) and, unlike IL-18, does not elicit a pro-inflammatory immune response but prevents it and is even involved in an anti-inflammatory response (Cavalli and Dinarello, 2018). IL-37 binds the alpha chain of the IL-18R and additionally interacts with IL-1R8 (also known as TIR8 or SIGIRR) rather than recruiting the beta chain of the IL-18R (as is the case with IL-18 binding) (Nold-Petry et al., 2015). This co-localization was also demonstrated in mouse cells (Nold-Petry et al., 2015). Other studies showed the mRNA of IL-18Rα and SIGIRR receptors on astrocytes and microglia (Andre et al., 2005). Notably, IL-18Rα has been shown to be expressed on astrocytes and microglia, and IL-18 is produced only by microglial cells, suggesting a signalling cascade running mainly through microglia with respect to IL-18 and IL-37 (Andre et al., 2005; Tsilioni et al., 2019). In addition, two recent studies focusing on the central and peripheral nervous systems have demonstrated the therapeutic potential of IL-37 in autism spectrum disorders (ASD) and multiple sclerosis (MS) (Tsilioni et al., 2019; Cavalli et al., 2019). Tsilioni et al., 2019 have demonstrated a reducing effect of inflammation on IL-37 expression in cultured human microglia. An important factor for the expression of IL-37 related to the instability sequence was also discovered in a mouse cell line. Bufler et al., 2004 showed that despite strong activation of the CMV promoter, expression of IL-37 could not be detected (Bufler et al., 2004). It was also shown that the specific mRNA was rapidly degraded. However, a significant and rapid increase in IL-37 mRNA could be achieved by an LPS stimulus (Bufler et al., 2004). Similarly, administration of recombinant IL-37 frequently exhibited beneficial effects on the outcome of various animal models of human diseases (Cavalli et al., 2016; Coll-Miró et al., 2016; Moretti et al., 2014; Wu et al., 2014). In addition, IL-37 has been shown to regulate cellular metabolism after an inflammatory stimulus (Su and Tao, 2021). In the last decade, metabolic changes have been described as an important determinant of immunological processes, as shown in macrophages after LPS stimulation (Su and Tao, 2021; O'Neill and Hardie, 2013). The LPS-induced increase in mTOR phosphorylation and decreased AMP-activated protein kinase activity were reversed by expression of IL-37 (Nold et al., 2010; Ballak et al., 2014; Nold-Petry et al., 2015; Su and Tao, 2021). In the present study, we used hIL-37tg mice to investigate the effect of IL-37 expression on the acute inflammatory processes induced by LPS or IL-1β administration. In addition, we crossed the APP/PS1 mouse model of AD with hIL-37tg mice to investigate the role of IL-37 expression during the chronic state of neuroinflammation and the consequences for the progression of AD pathology. Results Primary microglia from IL-37tg mice exhibit an inflammatory-suppressive response after LPS challenge in vitro To investigate the effect of IL-37 on microglial cell activation, the release of the pro-inflammatory cytokines IL-6, IL-1β, and TNF-α was analyzed after LPS stimulation of wild-type (WT) and IL-37 transgenic microglial cells (Figure 1A). Figure 1 with 1 supplement see all Download asset Open asset Primary microglial cells from IL-37tg mice showed decreased pro-inflammatory cytokine release after stimulation by LPS. (A) WT and IL-37tg primary microglial cells (P3-5) were plated and stimulated without LPS or with LPS. Cells were treated for 6 hr (B) and 24 hr (B–E). Cells from homozygous transgenic animals released less pro-inflammatory cytokines IL-6 (C), TNF- (D) and IL-1β (E) under different LPS concentration (B-E n=4–9). (F) IL37 mRNA was analyzed in IL-37tg microglial cells at specific intervals after addition of LPS. (G) Levels of IL-6 were measured from the same cells as in (F) and were detectable only after 24 hr (n=3). (H) Levels of IL-6 were measured in WT after addition of increasing concentrations of recombinant IL-37b and 100 ng LPS (H n=6–18). Data are presented as mean ± SEM. * p<0.05, ** p<0.01, *** p<0.001 compared to WT. (B+F + H: 1-way ANOVA with multiple comparison; C-E+G: t-test). Figure 1—source data 1 Release of pro-inflammatory cytokines by microglia after LPS stimulation. https://cdn.elifesciences.org/articles/75889/elife-75889-fig1-data1-v2.xlsx Download elife-75889-fig1-data1-v2.xlsx First, IL-6 secretion in heterozygous (IL-37wt/tg) and homozygous (IL-37tg/tg) IL-37 transgenic primary microglia was analyzed and compared to IL-6 secretion of WT microglia upon LPS stimulation. The results showed that the amounts of IL-6 secreted by microglial cells from homozygous IL-37 transgenic (IL-37tg/tg) mice were significantly reduced compared to microglial cells from control mice after 24 hr of stimulation with 100 ng/ml and 1 µg/ml LPS and additionally also 6 hr after stimulation with 1 µg/ml LPS (F(2,11)=7.941 p=0.007; p=0.007; p=0.054; F(2,11)=3.915 p=0.052; p=0.043; p=0.359; F(2,9)=12.74 p=0.002; p=0.004; p=0.009) (Figure 1B). Microglial cells from heterozygous IL-37 transgenic mice (IL-37wt/tg) also showed decreased IL-6 secretion, but only after 6 hr of stimulation with 1 µg/ml LPS (F(2,9)=12.74 p=0.002; p=0.009) (Figure 1B). Thus, the immunosuppressive effect of transgenic expression of IL-37 on primary microglia was demonstrated only in this experiment by differences between hetero- and homozygous IL-37 transgenic mice. All subsequent experiments were analyzed using homozygous (IL-37tg/tg) IL-37 transgenic mice (referred to as IL-37tg). Further analysis also confirmed the reduction in inflammatory mediators by measuring the release of IL-6 when other concentrations of the inflammatory stimulus were examined (Figure 1C) and could be extended by the significantly reduced release of TNF-α (Figure 1D) and IL-1β (Figure 1E), compared with primary microglial cells from control mice (IL-6: p=0.1007; p=0.0024; p=0.0001; TNF-α: p=0.0038; p<0.0001; p<0.0001; IL-1β: p=0.0295; p=0.0001; p<0.0001). Remarkably, LPS stimulation caused a detectable increase in the level of transgenic IL37 mRNA after 1 hr, which remained elevated in the following hours up to 24 hr post stimulation (F(7,15)=2.629 p=0.05509; p=0.0171, p=0.0086, p=0.0238) (Figure 1F). As mentioned previously, the amount of IL-6 protein in the supernatant of the same cultures was significantly reduced when IL-37tg microglial cells were compared to identically stimulated control cells (p<0.0001) (Figure 1G). Examining inflammatory responses in primary astrocytes as a different group of glial cells, we did not detect decreased levels of IL-6 and TNF-α in IL-37tg cells 24 hr after LPS stimulation (100 ng/ml) compared with WT primary astrocytic cells (Figure 1—figure supplement 1A,B), confirming the importance of anti-inflammatory IL-37 signaling, which may proceed via microglia but not astrocytes. To investigate the potential effect of recombinant IL-37 (rIL-37) in inhibiting LPS-induced release of proinflammatory cytokines (here IL-6) by microglia, primary WT microglial cells were pretreated with either 100 ng/mL or 500 ng/mL rIL-37 for 2 hr and then stimulated with increasing concentrations of LPS. Pretreatment with rIL-37 was chosen because microglial cells from IL-37tg mice had very low basal expression of IL-37 even in the absence of LPS (Figure 1F). Therefore, the response of WT microglial cells to LPS in the presence of different concentrations of rIL-37 was examined here. After LPS induction, microglial cells pretreated with the higher concentration of rIL-37 showed a significant decrease in the release of IL-6 compared with cells pretreated with rIL-37 vehicle (PBS) (F(2,30)=5.135 p=0.0121; p=0.0133; F(2,30)=3.512 p=0.0426; p=0.0498) (Figure 1H). Taken together, these results indicate that microglial cells in particular release lower levels of pro-inflammatory cytokines upon acute inflammatory stimulation in the presence of IL-37. Metabolomic profiling of microglial cells from IL-37tg mice reveals an attenuated metabolic response associated with inflammation after LPS stimulation in vitro Recent studies have discovered several metabolic intermediates that contribute directly to immune function. Among them, the TCA cycle-related metabolites succinate and itaconate are novel markers associated with pro-inflammatory macrophage activation and function (He et al., 2021; Michelucci et al., 2021; Mills et al., 2021). To address the question of whether microglial cells expressing the anti-inflammatory cytokine IL-37 are further capable of modulating inflammation-related metabolic changes, we performed intracellular metabolomic analysis of control and IL-37tg microglial cells treated with 10 ng/ml LPS for 24 hr. As expected, many metabolites were significantly elevated in LPS-treated control cells, including itaconate and succinate, both metabolic markers for proinflammatory activation of macrophages (Figure 2A; Michelucci et al., 2021; Tannahill et al., 2013). Levels of both metabolites were significantly less elevated in IL-37tg microglial cells, indicating an attenuated pro-inflammatory response at the metabolic level (Figure 2B and C) (itaconate F(1,20)=174.9 p<0.0001; p<0.0001; p<0.0001; F(1,20)=27.55 p<0.0001; p<0.0001; succinate F(1,20)=98.40 p<0.0001; p<0.0001; p=0.0005; F(1,20)=17.01 p=0.0005; p<0.0001). This is consistent with the profiles of other metabolites of central carbon metabolism showing modest effects after LPS treatment (Figure 2A). We conclude that IL-37tg microglial cells release lower levels of pro-inflammatory cytokines than control cells after LPS stimulation and that IL-37 expression in microglial cells limits LPS-induced pro-inflammatory metabolic reprogramming. Figure 2 Download asset Open asset Primary microglial cells isolated from IL-37tg mice exhibited reduced levels of inflammation-associated intracellular metabolites after stimulation with LPS. WT and IL-37tg microglia were stimulated with 10 ng/ml LPS (based on highly sensitive metabolomics assessments). Metabolomic analysis was performed on these cells. (A) Heatmap of identified significantly altered metabolites after or without LPS stimulation (described as Z-score). (B–C) Significant effects in WT, treated with LPS, were seen with respect to itaconate (B) and succinate (C), whereas these changes were significantly reduced in IL-37tg microglial cells treated with LPS compared with WT cells (n=11). Data are presented as mean ± SEM. *** p<0.001 (two-way ANOVA with multiple comparison). Figure 2—source data 1 Inflammation-associated intracellular metabolites in primary microglia after LPS stimulation. https://cdn.elifesciences.org/articles/75889/elife-75889-fig2-data1-v2.xlsx Download elife-75889-fig2-data1-v2.xlsx Microglial activation and inflammatory responses are reduced after LPS challenge in IL-37tg mice To test whether the anti-inflammatory properties of IL-37 on microglial cells observed in vitro studies, are similar in vivo, we intraperitoneally injected adult (3–8 month-old) homozygous IL-37tg mice (referred to as IL-37tg) and age-matched control animals with either saline (vehicle control group) or LPS (2x0.5 mg/kg) (Figure 3A). Both experimental groups showed significant weight loss in response to systemic LPS injection, but the effect was significantly higher in control mice than in IL-37tg mice (weight loss F(1,17)=220.5 p<0.0001; p<0.0001; p<0.0001; F(1,41)=1.486 p=0.2299; p=0.0139) (Figure 3B). We next examined the effect of systemic administration of LPS on neuroinflammation by using brain homogenates for ELISA assays and also by isolating microglia from the brains of controls and LPS-treated animals for FACS analyzes. Control mice treated with LPS had a significantly higher percentage of CD68-expressing microglial cells (gated on the CD11b+/CD45low population) (CD68 F(1,6)=19.52 p=0.0045; p=0.0017; p>0.9999; F(1,6)=48.42 p=0.0004; p=0.0001) (Figure 3C–D) compared to the cells of control animals treated with saline. Similarly, IL-1β levels in the brain of LPS-treated WT mice were significantly higher than those of saline-treated WT controls (IL-1β F(1,7)=9.399 p=0.0182; p=0.0244; p=0.7541; F(1,7)=3.182 p=0.0935; p=0.0366) (Figure 3E). Remarkably, IL-37tg animals showed no significant changes in CD68-expressing microglia and IL-1β levels when challenged with LPS in the same manner compared with matched controls (Figure 3C–E). Further analysis of pro-inflammatory cytokines IL-6 and TNF-α showed no significant changes between WT and IL-37tg mice treated with LPS and control groups, but a trend toward higher levels of IL-6 was observed in WT brain homogenates after LPS challenge (Figure 3—figure supplement 1A,B). Further investigation of cell populations in the brains of WT and IL-37tg mice after LPS stimulation underscored the importance of the IL-37 response, particularly in microglial cells (Figure 3—figure supplement 2A-E), whereas macrophages (gated on the CD11b+/CD45high population) showed no changes in CD68-expressing cells after LPS stimulation or between genotypes (Figure 3—figure supplement 2F-H). In addition, analysis of cell numbers in all experimental groups revealed a generally high number of microglial cells in the brain of the animals (Figure 3—figure supplement 2D and K) and, in contrast, very low numbers of macrophages (Figure 3—figure supplement 2G and K) and leukocytes (gated on the CD11b-/CD45high population) (Figure 3—figure supplement 2J-K), again highlighting the important role of microglia in this scenario. Figure 3 with 2 supplements see all Download asset Open asset IL-37tg mice showed decreased pro-inflammatory cytokine release and less activated microglia after the stimulus of LPS. (A) WT and IL-37tg mice were stimulated with saline or LPS. (B) IL-37tg animals exhibited significantly less weight loss compared to WT mice. However, IL-37tg mice also had a significant weight change compared to saline treated mice (n=10–22). Microglial cell activation was analyzed by FACS method. (C–D) Microglial cells were identified as CD11b+ and CD45low cells and analyzed for CD68 expression. IL-37tg mice had a lower percentage of cells with CD68 expression compared with WT mice after LPS stimulation (n=4) (C–D). (E) In addition, WT mice exhibited a significant increase in IL-1β levels after LPS treatment, whereas IL-37tg mice did not (n=6–8). (F–I) Morphological analysis of microglial cells showed an increased number of IBA-1-positive cells in WT animals treated with LPS compared with saline-treated animals. In contrast, there is no increased IBA-1-positive cell number in IL-37tg animals after LPS stimulation (n=9–18; n=18–30 cells for processes). (J) Representative images of IBA-1-positive cells (red) and DAPI (blue); scale bar 40 µm. Data are shown as mean ± SEM. * p<0.05, ** p<0.01, *** p<0.001, (B-I: 2-way ANOVA with multiple comparison). Figure 3—source data 1 Neuroinflammatory status of mouse brain after systemic LPS challenge. https://cdn.elifesciences.org/articles/75889/elife-75889-fig3-data1-v2.xlsx Download elife-75889-fig3-data1-v2.xlsx The activation feature of microglial cells is reflected in the total number of microglial cells in the brain parenchyma and the number of primary processes of these CNS resident immune cells. For example, a higher number of IBA-1-positive cells and a reduced number of primary processes correlate with increased microglial activation (Hanisch and Kettenmann, 2021; Papageorgiou et al., 2015; Wolf et al., 2017). Therefore, we performed immunostaining with the known microglial marker IBA-1 on brain sections obtained from the animals of both genotypes treated with either saline or LPS (Figure 3F–J). A significant increase in the number of IBA-1 positive cells was observed in the CA1 subregion of the hippocampus and in the cortex of LPS-treated animals compared with saline-treated control animals. However, in the IL-37tg mice, LPS did not result in a significant increase in the number of microglial cells (IBA-1 CA1 F(1,25)=5.222 p=0.0311; p=0.0024; p>0.9999; F(1,34)=4.951 p=0.0328; p=0.0027;; IBA-1 Cx F(1,25)=15.97 p=0.0005; p=0.0002; p=0.3234; F(1,34)=5.159 p=0.0296; p=0.0054) (Figure 3F and H). Further analysis of the number of microglial primary processes showed no differences between animals in the control and the IL-37tg groups treated with either saline or LPS, except that microglial primary processes were significantly increased in the cortex of IL-37tg mice treated with LPS compared with saline-treated IL-37tg mice, which may indicate more branched microglial features (processes CA1 F(1,46)=1.066; p>0.9999; p=0.6229; processes Cx F(1,104)=9.865; p=0.1401; p=0.0232) (Figure 3G1). Overall, these results demonstrate the anti-inflammatory effect of IL-37 expression on brain after LPS mediated via microglial cells. IL-37tg mice are from and neuronal deficits after LPS challenge Neuroinflammation has been shown to hippocampal function (Hosseini et al., 2018; et al., studies indicate a significant of neuroinflammation after systemic LPS we that IL-37 also have a beneficial effect on hippocampal function and Therefore, as described we injected control and IL-37tg animals with either saline or LPS for subsequent analysis of neuronal function and examined long-term the of to change which is a cellular correlate of learning and memory processes and To this we induced long-term potentiation (LTP) at the to CA1 in the After of we observed significantly impaired in the acute hippocampal of control mice treated with LPS compared to saline (Figure In contrast, IL-37tg animals treated with LPS did not show deficits in compared to saline treated IL-37tg animals (Figure differences were also in the of of the (Figure Figure Download asset Open asset IL-37tg mice showed and loss of spine after stimulation by LPS compared with WT animals. (A) WT animals stimulated with LPS showed significant of compared with WT, which were treated with saline. (B) In contrast, IL-37tg mice showed no significant of after LPS of after was significantly lower in WT mice treated with LPS, IL-37tg mice showed no significant differences of mice of acute in of the CA1 hippocampal and in the was significantly decreased in WT mice treated with LPS, whereas spine of IL-37tg animals treated with LPS was not of mice of and (F) Representative images of of hippocampal CA1 in the groups were scale bar µm. (G) WT acute stimulated with LPS showed significant of compared with WT acute treated with (H) In contrast, acute from IL-37tg mice showed no significant of after LPS of after was significantly lower in acute from WT mice treated with LPS, whereas from IL-37tg mice showed no significant differences of mice of acute Data are presented as mean ± SEM. * p<0.05, *** p<0.001, ANOVA with multiple comparison). Figure data 1 of after LPS challenge. Download To the effects of IL-37 on neuronal we analyzed the spine of hippocampal from all experimental are the of and were on the of CA1 as well as on the of A significant decrease in the of of CA1 and cells was observed in control mice treated with LPS compared with saline-treated mice CA1 p<0.0001; p<0.0001; p<0.0001; p<0.0001; p>0.9999; (Figure to the the of of from IL-37tg animals was when and mice were (Figure In these results demonstrate a effect of LPS on that can be by IL-37. the that peripheral immune cells in IL-37tg mice also IL-37 after LPS challenge and the systemic immune response, the question whether IL-37 have a similar effect directly in the CNS after LPS stimulation. To demonstrate the beneficial effect of IL-37 in the CNS without the influence of peripheral cells, experiment was Here, acute hippocampal from control and IL-37tg animals were and stimulated with LPS in for 2 hr after a In the control groups, the sections were in further results that IL-37 expression in the acute of IL-37tg mice to be to the impairments in after LPS administration. This is in to the significant of after LPS administration in acute hippocampal of control mice WT (Figure no of was observed in acute of IL-37tg mice when treated with LPS IL-37tg (Figure This effect was also in the data for the last of the which the of (Figure results demonstrate that local IL-37 expression in the brain can prevent the effects of LPS on neuronal function. IL-37 inflammatory response in and