Topical astilbin ameliorates imiquimod‐induced psoriasis‐like skin lesions in SKH‐1 mice via suppression dendritic cell‐Th17 inflammation axis

Astilbin, an essential component of Rhizoma smilacis glabrae, exerts significant antioxidant and anti‐inflammatory effects against various autoimmune diseases. We have previously reported that astilbin decreases proliferation and improves differentiation of HaCaT keratinocytes in a psoriatic model. The present study was designed to evaluate the potential therapeutic effects of topical administration of astilbin on an imiquimod (IMQ)‐induced psoriasis‐like murine model and to reveal their underlying mechanisms. Topical administration of astilbin at a lower dose alleviated IMQ‐induced psoriasis‐like skin lesions by inducing the differentiation of epidermal keratinocytes in mice, and the therapeutic effect was even better than that of calcipotriol. Moreover, the inflammatory skin disorder was relieved by astilbin treatment characterized by a reduction in both IL‐17‐producing T cell accumulation and psoriasis‐specific cytokine expression in skin lesions. Furthermore, we found that astilbin inhibited R837‐induced maturation and activation of bone marrow‐derived dendritic cells and decreased the expression of pro‐inflammatory cytokines by downregulating myeloid differentiation factor 88. Our findings provide the convincing evidence that lower doses of astilbin might attenuate psoriasis by interfering with the abnormal activation and differentiation of keratinocytes and accumulation of IL‐17‐producing T cells in skin lesions. Our results strongly support the pre‐clinical application of astilbin for psoriasis treatment.     

Synovial tissue‐derived extracellular vesicles induce chondrocyte inflammation and degradation via NF‐κB signalling pathway: An in vitro study

Osteoarthritis (OA) is a whole‐joint disease characterized by synovial inflammation and cartilage degeneration. However, the relationship between synovial inflammation and cartilage degeneration remains unclear. The modified Hulth''s method was adopted to establish a knee OA (KOA) rabbit model. Synovial tissue was collected after 8 weeks, and synovial tissue‐derived extracellular vesicles (ST‐EVs) were extracted by filtration combined with size exclusion chromatography (SECF), followed by identification through transmission electron microscopy (TEM), nanoparticle tracer analysis (NTA) and Western blot (WB). The collagenase digestion method was used to extract normal rabbit chondrocytes, which were then treated with the SF‐EVs to observe the effect and mechanism of SF‐EVs on chondrocytes. The morphology, particle size and labelled protein marker detection confirmed that SECF successfully extract ST‐EVs. The ST‐EVs in the KOA state significantly inhibited chondrocyte proliferation and promoted chondrocytes apoptosis. Moreover, the ST‐EVs also promoted the expression of pro‐inflammatory cytokines (IL‐1β, IL‐6, TNF‐α and COX‐2) and cartilage degradation‐related enzymes (MMP13, MMP9 and ADAMTS5) in the chondrocytes. Mechanistically, the ST‐EVs significantly promoted the activation of NF‐κB signalling pathway in chondrocytes. Inhibition the activation of the NF‐κB signalling pathway significantly rescued the expression of inflammatory cytokines and cartilage degradation‐related enzymes in the ST‐EVs–induced chondrocytes. In conclusion, the ST‐EVs promote chondrocytes inflammation and degradation by activating the NF‐κB signalling pathway, providing novel insights into the occurrence and development of OA.     

Vitamin B6 prevents excessive inflammation by reducing accumulation of sphingosine‐1‐phosphate in a sphingosine‐1‐phosphate lyase–dependent manner

Vitamin B6 is necessary to maintain normal metabolism and immune response, especially the anti‐inflammatory immune response. However, the exact mechanism by which vitamin B6 plays the anti‐inflammatory role is still unclear. Here, we report a novel mechanism of preventing excessive inflammation by vitamin B6 via reduction in the accumulation of sphingosine‐1‐phosphate (S1P) in a S1P lyase (SPL)‐dependent manner in macrophages. Vitamin B6 supplementation decreased the expression of pro‐inflammatory cytokines by suppressing nuclear factor‐κB and mitogen‐activated protein kinases signalling pathways. Furthermore, vitamin B6–reduced accumulation of S1P by promoting SPL activity. The anti‐inflammatory effects of vitamin B6 were inhibited by S1P supplementation or SPL deficiency. Importantly, vitamin B6 supplementation protected mice from lethal endotoxic shock and attenuated experimental autoimmune encephalomyelitis progression. Collectively, these findings revealed a novel anti‐inflammatory mechanism of vitamin B6 and provided guidance on its clinical use.     

Pseudolaric acid B ameliorates synovial inflammation and vessel formation by stabilizing PPARγ to inhibit NF‐κB signalling pathway

Synovial macrophage polarization and inflammation are essential for osteoarthritis (OA) development, yet the molecular mechanisms and regulation responsible for the pathogenesis are still poorly understood. Here, we report that pseudolaric acid B (PAB) attenuated articular cartilage degeneration and synovitis during OA. PAB, a diterpene acid, specifically inhibited NF‐κB signalling and reduced the production of pro‐inflammatory cytokines, which further decreased M1 polarization and vessel formation. We further provide in vivo and in vitro evidences that PAB suppressed NF‐κB signalling by stabilizing PPARγ. Using PPARγ antagonist could abolish anti‐inflammatory effect of PAB and rescue the activation of NF‐κB signalling during OA. Our findings identify a previously unrecognized role of PAB in the regulation of OA and provide mechanisms by which PAB regulates NF‐κB signalling through PPARγ, which further suggest targeting synovial inflammation or inhibiting vessel formation at early stage could be an effective preventive strategy for OA.     

Tacrolimus alleviates LPS‐induced AKI by inhibiting TLR4/MyD88/NF‐κB signalling in mice

Lipopolysaccharide (LPS)‐induced sepsis‐associated acute kidney injury (SA‐AKI) is a model of clinical serious care syndrome, with high morbidity and mortality. Tacrolimus (TAC), a novel immunosuppressant that inhibits inflammatory response, plays a pivotal role in kidney diseases. In this study, LPS treated mice and cultured podocytes were used as the models of SA‐AKI in vivo and in vitro, respectively. Medium‐ and high‐dose TAC administration significantly attenuated renal function and renal pathological manifestations at 12, 24 and 48 h after LPS treatment in mice. Moreover, the Toll‐like receptor 4 (TLR4)/myeloid differential protein‐88 (MyD88)/nuclear factor‐kappa (NF‐κB) signalling pathway was also dramatically inhibited by medium‐ and high‐dose TAC administration at 12, 24 and 48 h of LPS treatment mice. In addition, TAC reversed LPS‐induced podocyte cytoskeletal injury and podocyte migratory capability. Our findings indicate that TAC has protective effects against LPS‐induced AKI by inhibiting TLR4/MyD88/NF‐κB signalling pathway and podocyte dysfunction, providing another potential therapeutic effects for the LPS‐induced SA‐AKI.     

Astilbin prevents osteoarthritis development through the TLR4/MD‐2 pathway

Osteoarthritis has become one of the main diseases affecting the life of many elderly people with high incidence of disability, and local chronic inflammation in the joint cavity is the most crucial pathological feature of osteoarthritis. Astilbin is the main active component in a variety of natural plants such as Hypericum perforatum and Sarcandra glabra, which possess antioxidant and anti‐inflammatory effects. At present, there is no study about the protective effect of Astilbin for osteoarthritis. The purpose of this study was to investigate the effect of Astilbin in human OA chondrocytes and mouse OA model, which was established by surgery‐mediated destabilization of the medial meniscus (DMM). In vitro, we found that Astilbin pre‐treatment inhibited lipopolysaccharide (LPS)‐induced overproduction of inflammation‐correlated cytokines such as nitric oxide (NO), prostaglandin E2 (PGE2), tumour necrosis factor α (TNF‐α) and interleukin 6 (IL‐6), and suppressed overexpression of inflammatory enzymes such as inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX‐2). Astilbin, on the other hand, prevented the LPS‐induced degradation of extracellular matrix (ECM) by down‐regulating MMP13 (matrix metalloproteinases 13) and ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5). Moreover, by inhibiting the formation of the TLR4/MD‐2/LPS complex, Astilbin blocked LPS‐induced activation of TLR4/NF‐κB signalling cascade. In vivo, Astilbin showed the chondro‐protective effect in the surgical‐induced OA mouse models. In conclusion, our findings provided evidence that develops Astilbin as a potential therapeutic drug for OA patients.     

Oral intake of Lactobacillus plantarum L‐14 extract alleviates TLR2‐ and AMPK‐mediated obesity‐associated disorders in high‐fat‐diet‐induced obese C57BL/6J mice

ObjectivesWhether periodic oral intake of postbiotics positively affects weight regulation and prevents obesity‐associated diseases in vivo is unclear. This study evaluated the action mechanism of Lactobacillus plantarum L‐14 (KTCT13497BP) extract and the effects of its periodic oral intake in a high‐fat‐diet (HFD) mouse model.Materials and methodsMouse pre‐adipocyte 3T3‐L1 cells and human bone marrow mesenchymal stem cells (hBM‐MSC) were treated with L‐14 extract every 2 days during adipogenic differentiation, and the mechanism underlying anti‐adipogenic effects was analysed at cellular and molecular levels. L‐14 extract was orally administrated to HFD‐feeding C57BL/6J mice every 2 days for 7 weeks. White adipose tissue was collected and weighed, and liver and blood serum were analysed. The anti‐adipogenic mechanism of exopolysaccharide (EPS) isolated from L‐14 extract was also analysed using Toll‐like receptor 2 (TLR2) inhibitor C29.ResultsL‐14 extract inhibited 3T3‐L1 and hBM‐MSC differentiation into mature adipocytes by upregulating AMPK signalling pathway in the early stage of adipogenic differentiation. The weight of the HFD + L‐14 group (31.51 ± 1.96 g) was significantly different from that of the HFD group (35.14 ± 3.18 g). L‐14 extract also significantly decreased the serum triacylglycerol/high‐density lipoprotein cholesterol ratio (an insulin resistance marker) and steatohepatitis. In addition, EPS activated the AMPK signalling pathway by interacting with TLR2, consequently inhibiting adipogenesis.ConclusionsEPS from L‐14 extract inhibits adipogenesis via TLR2 and AMPK signalling pathways, and oral intake of L‐14 extract improves obesity and obesity‐associated diseases in vivo. Therefore, EPS can be used to prevent and treat obesity and metabolic disorders.     

GM‐CSF suppresses antioxidant signaling and drives IL‐1β secretion through NRF2 downregulation

GM‐CSF is a potent inflammatory cytokine regulating myeloid cell differentiation, hematopoiesis, and various other functions. It is functionally associated with a number of inflammatory pathologies including rheumatoid arthritis and inflammatory bowel disease. GM‐CSF has been found to promote NLRP3‐dependent IL‐1β secretion, which may have a significant role in driving inflammatory pathologies. However, the molecular mechanisms remain unknown. Here, we show that GM‐CSF induces IL‐1β secretion through a ROS‐dependent pathway. TNF is required for reactive oxygen species (ROS) generation that strikingly does not promote NLRP3 activation, but instead drives ubiquitylation of IL‐1β, promoting its cleavage through basal NRLP3 activity. GM‐CSF regulates this pathway through suppression of antioxidant responses via preventing upregulation of NRF2. Thus, the pro‐inflammatory effect of GM‐CSF on IL‐1β is through suppression of antioxidant responses, which leads to ubiquitylation of IL‐1β and enhanced processing. This study highlights the role of metabolic regulation of inflammatory signaling and reveals a novel mechanism for GM‐CSF to promote inflammation.     

B‐cell capacity for differentiation changes with age

BackgroundAge‐related immune deficiencies are thought to be responsible for increased susceptibility to infection in older adults, with alterations in lymphocyte populations becoming more prevalent over time. The loss of humoral immunity in ageing was attributed to the diminished numbers of B cells and the reduced ability to generate immunoglobulin.AimsTo compare the intrinsic B‐cell capacity for differentiation into mature plasma cells (PCs), between young and old donors, using in vitro assays, providing either effective T‐cell help or activation via TLR engagement.MethodsB cells were isolated from healthy individuals, in younger (30–38 years) and older (60–64 years) donors. An in vitro model system of B‐cell differentiation was used, analysing 5 differentiation markers by flow cytometry, under T‐dependent (TD: CD40/BCR stimulation) or T‐independent (TI: TLR7/BCR activation) conditions. Antibody secretion was measured by ELISA and gene expression using qPCR.ResultsTI and TD differentiation resulted in effective proliferation of B cells followed by their differentiation into PC. B‐cell‐executed TI differentiation was faster, all differentiation marker and genes being expressed earlier than under TD differentiation (day 6), although generating less viable cells and lower antibody levels (day 13). Age‐related differences in B‐cell capacity for differentiation were minimal in TD differentiation. In contrast, in TI differentiation age significantly affected proliferation, viability, differentiation, antibody secretion and gene expression, older donors being more efficient.ConclusionAltogether, B‐cell differentiation into PC appeared similar between age groups when provided with T‐cell help, in contrast to TI differentiation, where multiple age‐related changes suggest better capacities in older donors. These new findings may help explain the emergence of autoantibodies in ageing.     

Anti‐inflammatory properties of lemon‐derived extracellular vesicles are achieved through the inhibition of ERK/NF‐κB signalling pathways

Chronic inflammation is associated with the occurrence of several diseases. However, the side effects of anti‐inflammatory drugs prompt the identification of new therapeutic strategies. Plant‐derived extracellular vesicles (PDEVs) are gaining increasing interest in the scientific community for their biological properties. We isolated PDEVs from the juice of Citrus limon L. (LEVs) and characterized their flavonoid, limonoid and lipid contents through reversed‐phase high‐performance liquid chromatography coupled to electrospray ionization quadrupole time‐of‐flight mass spectrometry (RP‐HPLC–ESI‐Q‐TOF‐MS). To investigate whether LEVs have a protective role on the inflammatory process, murine and primary human macrophages were pre‐treated with LEVs for 24 h and then were stimulated with lipopolysaccharide (LPS). We found that pre‐treatment with LEVs decreased gene and protein expression of pro‐inflammatory cytokines, such as IL‐6, IL1‐β and TNF‐α, and reduced the nuclear translocation and phosphorylation of NF‐κB in LPS‐stimulated murine macrophages. The inhibition of NF‐κB activation was associated with the reduction in ERK1‐2 phosphorylation. Furthermore, the ability of LEVs to decrease pro‐inflammatory cytokines and increase anti‐inflammatory molecules was confirmed ex vivo in human primary T lymphocytes. In conclusion, we demonstrated that LEVs exert anti‐inflammatory effects both in vitro and ex vivo by inhibiting the ERK1‐2/NF‐κB signalling pathway.     

Effect of TLR4/MyD88/NF‐kB axis in paraventricular nucleus on ventricular arrhythmias induced by sympathetic hyperexcitation in post‐myocardial infarction rats

Sympathetic activation after myocardial infarction (MI) leads to ventricular arrhythmias (VAs), which can result in sudden cardiac death (SCD). The toll‐like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)/nuclear factor‐kappa B (NF‐kB) axis within the hypothalamic paraventricular nucleus (PVN), a cardiac‐neural sympathetic nerve centre, plays an important role in causing VAs. An MI rat model and a PVN‐TLR4 knockdown model were constructed. The levels of protein were detected by Western blotting and immunofluorescence, and localizations were visualized by multiple immunofluorescence staining. Central and peripheral sympathetic activation was visualized by immunohistochemistry for c‐fos protein, renal sympathetic nerve activity (RSNA) measurement, heart rate variability (HRV) analysis and norepinephrine (NE) level detection in serum and myocardial tissue measured by ELISA. The arrhythmia scores were measured by programmed electrical stimulation (PES), and cardiac function was detected by the pressure–volume loop (P‐V loop). The levels of TLR4 and MyD88 and the nuclear translocation of NF‐kB within the PVN were increased after MI, while sympathetic activation and arrhythmia scores were increased and cardiac function was decreased. However, inhibition of TLR4 significantly reversed these conditions. PVN‐mediated sympathetic activation via the TLR4/MyD88/NF‐kB axis ultimately leads to the development of VAs after MI.     

p38α‐MAPK‐deficient myeloid cells ameliorate symptoms and pathology of APP‐transgenic Alzheimer's disease mice

Alzheimer''s disease (AD), the most common cause of dementia in the elderly, is pathologically characterized by extracellular deposition of amyloid‐β peptides (Aβ) and microglia‐dominated inflammatory activation in the brain. p38α‐MAPK is activated in both neurons and microglia. How p38α‐MAPK in microglia contributes to AD pathogenesis remains unclear. In this study, we conditionally knocked out p38α‐MAPK in all myeloid cells or specifically in microglia of APP‐transgenic mice, and examined animals for AD‐associated pathologies (i.e., cognitive deficits, Aβ pathology, and neuroinflammation) and individual microglia for their inflammatory activation and Aβ internalization at different disease stages (e.g., at 4 and 9 months of age). Our experiments showed that p38α‐MAPK‐deficient myeloid cells were more effective than p38α‐MAPK‐deficient microglia in reducing cerebral Aβ and neuronal impairment in APP‐transgenic mice. Deficiency of p38α‐MAPK in myeloid cells inhibited inflammatory activation of individual microglia at 4 months but enhanced it at 9 months. Inflammatory activation promoted microglial internalization of Aβ. Interestingly, p38α‐MAPK‐deficient myeloid cells reduced IL‐17a‐expressing CD4‐positive lymphocytes in 9 but not 4‐month‐old APP‐transgenic mice. By cross‐breeding APP‐transgenic mice with Il‐17a‐knockout mice, we observed that IL‐17a deficiency potentially activated microglia and reduced Aβ deposition in the brain as shown in 9‐month‐old myeloid p38α‐MAPK‐deficient AD mice. Thus, p38α‐MAPK deficiency in all myeloid cells, but not only in microglia, prevents AD progression. IL‐17a‐expressing lymphocytes may partially mediate the pathogenic role of p38α‐MAPK in peripheral myeloid cells. Our study supports p38α‐MAPK as a therapeutic target for AD patients.     

Dental pulp stem cell‐derived exosomes alleviate cerebral ischaemia‐reperfusion injury through suppressing inflammatory response

ObjectivesThe study aimed to determine whether dental pulp stem cell‐derived exosomes (DPSC‐Exos) exert protective effects against cerebral ischaemia‐reperfusion (I/R) injury and explore its underlying mechanism.Materials and MethodsExosomes were isolated from the culture medium of human DPSC. Adult male C57BL/6 mice were subjected to 2 hours transient middle cerebral artery occlusion (tMCAO) injury followed by 2 hours reperfusion, after which singular injection of DPSC‐Exos via tail vein was administrated. Brain oedema, cerebral infarction and neurological impairment were measured on day 7 after exosomes injection. Then, oxygen‐glucose deprivation–reperfusion (OGD/R) induced BV2 cells were studied to analyse the therapeutic effects of DPSC‐Exos on I/R injury in vitro. Protein levels of TLR4, MyD88, NF‐κB p65, HMGB1, IL‐6, IL‐1β and TNF‐α were determined by western blot or enzyme‐linked immunosorbent assay. The cytoplasmic translocation of HMGB1 was detected by immunofluorescence staining.ResultsDPSC‐Exos alleviated brain oedema, cerebral infarction and neurological impairment in I/R mice. DPSC‐Exos inhibited the I/R‐mediated expression of TLR4, MyD88 and NF‐κB significantly. DPSC‐Exos also reduced the protein expression of IL‐6, IL‐1β and TNF‐α compared with those of the control both in vitro and in vivo. Meanwhile, DPSC‐Exos markedly decreased the HMGB1 cytoplasmic translocation induced by I/R damage.ConclusionsDPSC‐Exos can ameliorate I/R‐induced cerebral injury in mice. Its anti‐inflammatory mechanism might be related with the inhibition of the HMGB1/TLR4/MyD88/NF‐κB pathway.     

Nur77 Prevents Osteoporosis by Inhibiting the NF‐κB Signalling Pathway and Osteoclast Differentiation

Inflammation is a major risk factor for osteoporosis, and reducing inflammatory levels is important for the prevention of osteoporosis. Although nuclear receptor 77 (Nur77) protects against inflammation in a variety of diseases, its role in osteoporosis is unknown. Therefore, the main purpose of this study was to investigate the osteoprotective and anti‐inflammatory effects of Nur77. The microCT and haematoxylin and eosin staining results indicated that knockout of Nur77 accelerated femoral bone loss in mice. The enzyme‐linked immunosorbent assay (ELISA) results showed that knockout of Nur77 increased the serum levels of hsCRP and IL‐6. The expression levels of NF‐κB, IL‐6, TNF‐α and osteoclastogenesis factors (TRAP, NFATC1, Car2, Ctsk) in the femurs of Nur77 knockout mice were increased significantly. Furthermore, in vitro, shNur77 promoted the differentiation of RAW264.7 cells into osteoclasts by activating NF‐κB, which was confirmed by PDTC treatment. Mechanistically, Nur77 inhibited osteoclast differentiation by inducing IκB‐α and suppressing IKK‐β. In RAW264.7 cells, overexpression of Nur77 alleviated inflammation induced by siIκB‐α, while siIKK‐β alleviated inflammation induced by shNur77. Consistent with the in vivo studies, we found that compared with control group, older adults with high serum hsCRP levels were more likely to suffer from osteoporosis (OR = 1.76, p < 0.001). Our data suggest that Nur77 suppresses osteoclast differentiation by inhibiting the NF‐κB signalling pathway, strongly supporting the notion that Nur77 has the potential to prevent and treat osteoporosis.     

TLR2 and TLR7 mediate distinct immunopathological and antiviral plasmacytoid dendritic cell responses to SARS‐CoV‐2 infection

Understanding the molecular pathways driving the acute antiviral and inflammatory response to SARS‐CoV‐2 infection is critical for developing treatments for severe COVID‐19. Here, we find decreasing number of circulating plasmacytoid dendritic cells (pDCs) in COVID‐19 patients early after symptom onset, correlating with disease severity. pDC depletion is transient and coincides with decreased expression of antiviral type I IFNα and of systemic inflammatory cytokines CXCL10 and IL‐6. Using an in vitro stem cell‐based human pDC model, we further demonstrate that pDCs, while not supporting SARS‐CoV‐2 replication, directly sense the virus and in response produce multiple antiviral (interferons: IFNα and IFNλ1) and inflammatory (IL‐6, IL‐8, CXCL10) cytokines that protect epithelial cells from de novo SARS‐CoV‐2 infection. Via targeted deletion of virus‐recognition innate immune pathways, we identify TLR7‐MyD88 signaling as crucial for production of antiviral interferons (IFNs), whereas Toll‐like receptor (TLR)2 is responsible for the inflammatory IL‐6 response. We further show that SARS‐CoV‐2 engages the receptor neuropilin‐1 on pDCs to selectively mitigate the antiviral interferon response, but not the IL‐6 response, suggesting neuropilin‐1 as potential therapeutic target for stimulation of TLR7‐mediated antiviral protection.     

Machine learning identifies molecular regulators and therapeutics for targeting SARS‐CoV2‐induced cytokine release

Although 15–20% of COVID‐19 patients experience hyper‐inflammation induced by massive cytokine production, cellular triggers of this process and strategies to target them remain poorly understood. Here, we show that the N‐terminal domain (NTD) of the SARS‐CoV‐2 spike protein substantially induces multiple inflammatory molecules in myeloid cells and human PBMCs. Using a combination of phenotypic screening with machine learning‐based modeling, we identified and experimentally validated several protein kinases, including JAK1, EPHA7, IRAK1, MAPK12, and MAP3K8, as essential downstream mediators of NTD‐induced cytokine production, implicating the role of multiple signaling pathways in cytokine release. Further, we found several FDA‐approved drugs, including ponatinib, and cobimetinib as potent inhibitors of the NTD‐mediated cytokine release. Treatment with ponatinib outperforms other drugs, including dexamethasone and baricitinib, inhibiting all cytokines in response to the NTD from SARS‐CoV‐2 and emerging variants. Finally, ponatinib treatment inhibits lipopolysaccharide‐mediated cytokine release in myeloid cells in vitro and lung inflammation mouse model. Together, we propose that agents targeting multiple kinases required for SARS‐CoV‐2‐mediated cytokine release, such as ponatinib, may represent an attractive therapeutic option for treating moderate to severe COVID‐19.     

Interleukin‐37 improves T‐cell‐mediated immunity and chimeric antigen receptor T‐cell therapy in aged backgrounds

Aging‐associated declines in innate and adaptive immune responses are well documented and pose a risk for the growing aging population, which is predicted to comprise greater than 40 percent of the world''s population by 2050. Efforts have been made to improve immunity in aged populations; however, safe and effective protocols to accomplish this goal have not been universally established. Aging‐associated chronic inflammation is postulated to compromise immunity in aged mice and humans. Interleukin‐37 (IL‐37) is a potent anti‐inflammatory cytokine, and we present data demonstrating that IL‐37 gene expression levels in human monocytes significantly decline with age. Furthermore, we demonstrate that transgenic expression of interleukin‐37 (IL‐37) in aged mice reduces or prevents aging‐associated chronic inflammation, splenomegaly, and accumulation of myeloid cells (macrophages and dendritic cells) in the bone marrow and spleen. Additionally, we show that IL‐37 expression decreases the surface expression of programmed cell death protein 1 (PD‐1) and augments cytokine production from aged T‐cells. Improved T‐cell function coincided with a youthful restoration of Pdcd1, Lat, and Stat4 gene expression levels in CD4⁺ T‐cells and Lat in CD8⁺ T‐cells when aged mice were treated with recombinant IL‐37 (rIL‐37) but not control immunoglobin (Control Ig). Importantly, IL‐37‐mediated rejuvenation of aged endogenous T‐cells was also observed in aged chimeric antigen receptor (CAR) T‐cells, where improved function significantly extended the survival of mice transplanted with leukemia cells. Collectively, these data demonstrate the potency of IL‐37 in boosting the function of aged T‐cells and highlight its therapeutic potential to overcome aging‐associated immunosenescence.     

IL‐21 has a critical role in establishing germinal centers by amplifying early B cell proliferation

The proliferation and differentiation of antigen‐specific B cells, including the generation of germinal centers (GC), are prerequisites for long‐lasting, antibody‐mediated immune protection. Affinity for antigen determines B cell recruitment, proliferation, differentiation, and competitiveness in the response, largely through determining access to T cell help. However, how T cell‐derived signals contribute to these outcomes is incompletely understood. Here, we report how the signature cytokine of follicular helper T cells, IL‐21, acts as a key regulator of the initial B cell response by accelerating cell cycle progression and the rate of cycle entry, increasing their contribution to the ensuing GC. This effect occurs over a wide range of initial B cell receptor affinities and correlates with elevated AKT and S6 phosphorylation. Moreover, the resultant increased proliferation can explain the IL‐21‐mediated promotion of plasma cell differentiation. Collectively, our data establish that IL‐21 acts from the outset of a T cell‐dependent immune response to increase cell cycle progression and fuel cyclic re‐entry of B cells, thereby regulating the initial GC size and early plasma cell output.     

Acetylshikonin induces autophagy‐dependent apoptosis through the key LKB1‐AMPK and PI3K/Akt‐regulated mTOR signalling pathways in HL‐60 cells

Acetylshikonin (ASK) is a natural naphthoquinone derivative of traditional Chinese medicine Lithospermum erythrorhyzon. It has been reported that ASK has bactericidal, anti‐inflammatory and antitumour effects. However, whether ASK induces apoptosis and autophagy in acute myeloid leukaemia (AML) cells and the underlying mechanism are still unclear. Here, we explored the roles of apoptosis and autophagy in ASK‐induced cell death and the potential molecular mechanisms in human AML HL‐60 cells. The results demonstrated that ASK remarkably inhibited the cell proliferation, viability and induced apoptosis in HL‐60 cells through the mitochondrial pathway, and ASK promoted cell cycle arrest in the S‐phase. In addition, the increased formation of autophagosomes, the turnover from light chain 3B (LC3B) I to LC3B II and decrease of P62 suggested the induction of autophagy by ASK. Furthermore, ASK significantly decreased PI3K, phospho‐Akt and p‐p70S6K expression, while enhanced phospho‐AMP‐activated protein kinase (AMPK) and phospho‐liver kinase B1(LKB1) expression. The suppression of ASK‐induced the conversion from LC3B I to LC3B II caused by the application of inhibitors of AMPK (compound C) demonstrated that ASK‐induced autophagy depends on the LKB1/AMPK pathway. These data suggested that the autophagy induced by ASK were dependent on the activation of LKB1/AMPK signalling and suppression of PI3K/Akt/mTOR pathways. The cleavage of the apoptosis‐related markers caspase‐3 and caspase‐9 and the activity of caspase‐3 induced by ASK were markedly reduced by inhibitor of AMPK (compound C), an autophagy inhibitor 3‐methyladenine (3‐MA) and another autophagy inhibitor chloroquine (CQ). Taken together, our data reveal that ASK‐induced HL‐60 cell apoptosis is dependent on the activation of autophagy via the LKB1/AMPK and PI3K/Akt‐regulated mTOR signalling pathways.