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Microglia-induced inflammatory signaling and neuronal oxidative stress are mutually reinforcing processes central to the pathogenesis of neurodegenerative diseases. Recent studies have shown that extracts of dried Pheretima aspergillum (Lumbricus) can inhibit tissue fibrosis, mitochondrial damage, and asthma. However, the effects of Lumbricus extracts on neuroinflammation and neuronal damage have not been previously studied. Therefore, to evaluate the therapeutic potential of Lumbricus extract for neurodegenerative diseases, the current study assessed the extract’s anti-inflammatory and antioxidant activities in BV2 microglial cultures stimulated with lipopolysaccharide (LPS) along with its neuroprotective efficacy in mouse hippocampal HT22 cell cultures treated with excess glutamate. Lumbricus extract dose-dependently inhibited the LPS-induced production of multiple proinflammatory cytokines (tumor necrosis factor-α, interleukin (IL)-6, and IL-1β) and reversed the upregulation of proinflammatory enzymes (inducible nitric oxide synthase and cyclooxygenase-2). Lumbricus also activated the antioxidative nuclear factor erythroid 2-relayed factor 2/heme oxygenase-1 pathway and inhibited LPS-induced activation of the nuclear factor-κB/mitogen-activated protein kinases/NOD-like receptor family pyrin domain containing 3 inflammatory pathway. In addition, Lumbricus extract suppressed the glutamate-induced necrotic and apoptotic death of HT22 cells, effects associated with upregulated expression of antiapoptotic proteins, downregulation of pro-apoptotic proteins, and reduced accumulation of reactive oxygen species. Chromatography revealed that the Lumbricus extract contained uracil, hypoxanthine, uridine, xanthine, adenosine, inosine, and guanosine. Its effects against microglial activation and excitotoxic neuronal death reported herein support the therapeutic potential of Lumbricus for neurodegenerative diseases.

Gwakhyangjeonggi-san (GJS) is a traditional herbal medicine used in East Asia for the treatment of symptoms involving lower intestinal abnormalities; however, the effects of GJS on innate immunity and its cellular mechanisms of action have not been elucidated. In this study, we assessed the immune-enhancing activity and underlying mechanisms of GJS using RAW 264.7 murine macrophages. The results showed that GJS treatment significantly increased the secretion of nitric oxide and cytokines and their mRNA expression in macrophage RAW 264.7 cells without causing cytotoxicity. GJS treatment also significantly increased the production of reactive oxygen species, as well as inducing phagocytic activity, adhesion function, and migration ability, all of which improved the immune response. In addition, GJS activated nuclear factor-κB by promoting the phosphorylation and degradation of inhibitor of nuclear factor-κB alpha. Furthermore, GJS markedly increased the phosphorylation of mitogen-activated protein kinase in RAW 264.7 cells. These findings indicate that GJS has potential value as a dietary supplement for strengthening immunity.

Abstract Chronic viral infection impairs systemic immunity in the host; however, the mechanism underlying the dysfunction of immune cells in chronic viral infection is incompletely understood. In this study, we studied the lineage differentiation of hematopoietic stem cells (HSCs) during chronic viral infection to elucidate the changes in dendritic cell (DC) differentiation and subsequent impact on T cell functionality using a chronic lymphocytic choriomeningitis virus (LCMV) infection model. We first investigated the lineage differentiation of HSCs in the bone marrow (BM) to elucidate the modulation of immune cell differentiation and found that the populations highly restrained in their differentiation were common myeloid progenitors (CMPs) and common dendritic cell progenitors (CDPs). Of interest, the main immune cells infected with LCMV Clone 13 (CL13) in the BM were CD11b/c+ myeloid DCs. We next characterized CD11b+ DCs that differentiated during chronic LCMV infection. These DCs displayed a less immunogenic phenotype than DCs in naive or acutely infected mice, showing low expression of CD80 but high expression of PD-L1, B7-H4, IDO, TGF-β, and IL-10. Consequently, these CD11b+ DCs induced less effective CD8+ T cells and more Foxp3+ regulatory T (Treg) cells. Furthermore, CD11b+ DCs generated during CL13 infection could not induce effective CD8+ T cells specific to the antigens of newly invading pathogens. Our findings demonstrate that DCs generated from the BM during chronic viral infection cannot activate fully functional effector CD8+ T cells specific to newly incoming antigens as well as persistent antigens themselves, suggesting a potential cause of the functional alterations in the T cell immune response during chronic viral infection.

Arecae Pericarpium has been found to exert anti-migraine, antidepressant, and antioxidative effects. However, the mechanisms involved are unclear. This study explored the possibility that Arecae Pericarpium ethanol extract (APE) exerts neuroprotective effects against oxidative stress-induced neuronal cell death. Since glutamate excitotoxicity has been implicated in the pathogenesis and development of several neurodegenerative disorders, we explored the mechanisms of action of APE on oxidative stress-induced by glutamate. Our results revealed that pretreatment with APE prevents glutamate-induced HT22 cell death. APE also reduced both the levels of intracellular reactive oxygen species and the apoptosis of cells, while maintaining glutamate-induced mitochondrial membrane potentials. Western blotting showed that pretreatment with APE facilitates the upregulation of phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) phosphorylation; the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf-2); and the production of antioxidant enzymes, including catalase, glutamate-cysteine ligase catalytic subunits, NAD(P)H quinone oxidoreductase 1, and heme oxygenase (HO)-1. The administration of LY294002, a PI3K/Akt inhibitor, attenuated the neuroprotective effects of APE on oxidative stress-induced neuronal cell damage. This allowed us to infer that the protective effects of APE on oxidative damage to cells can be attributed to the PI3K/Akt-mediated Nrf-2/HO-1 signaling pathway.

Plant extracts are widely used as traditional medicines. Sophora flavescens Aiton-derived natural compounds exert various beneficial effects, such as anti-inflammatory, anticancer, antioxidant, and antiregenerative activities, through their bioactive compounds, including flavonoids and alkaloids. In the present study, we investigated the biological effects of an S. flavescens-derived flavonoid, trifolirhizin (trifol), on the stimulation of osteogenic processes during osteoblast differentiation. Trifol (>98% purity) was successfully isolated from the root of S. flavescens and characterized. Trifol did not exhibit cellular toxicity in osteogenic cells, but promoted alkaline phosphatase (ALP) staining and activity, with enhanced expression of the osteoblast differentiation markers, including Alp, ColI, and Bsp. Trifol induced nuclear runt-related transcription factor 2 (RUNX2) expression during the differentiation of osteogenic cells, and concomitantly stimulated the major osteogenic signaling proteins, including GSK3β, β-catenin, and Smad1/5/8. Among the mitogen-activated protein kinases (MAPKs), Trifol activated JNK, but not ERK1/2 and p38. Trifol also increased the osteoblast-mediated bone-forming phenotypes, including transmigration, F-actin polymerization, and mineral apposition, during osteoblast differentiation. Overall, trifol exhibits bioactive activities related to osteogenic processes via differentiation, migration, and mineralization. Collectively, these results suggest that trifol may serve as an effective phytomedicine for bone diseases such as osteoporosis.

Polyozellus multiplex, a wild mushroom belonging to Thelephoracea, is distributed in Korea, Japan, and China. Thelephoric acid (Thel), a terphenylquinone found in P. multiplex, reportedly exhibits beneficial effects, including antioxidant, anticancer, and neuroprotective activities. Herein, we extracted Thel from P. multiplex (>95.8% purity) and examined its osteogenic effects on pre-osteoblasts. Thel exerted no cytotoxicity in pre-osteoblasts. Based on alkaline phosphatase staining and activity, Thel promoted osteoblast differentiation and bone matrix mineralization. Biochemical investigations revealed that Thel enhanced nuclear runt-related transcription factor 2 (RUNX2) expression and accumulation via Smad1/5/8 phosphorylation, while exhibiting synergistic activities following cotreatment with bone morphogenetic protein 2 or fibroblast growth factor 2 in pre-osteoblast cultures. Thel increased cell adhesion and migration in differentiating osteoblasts by upregulating matrix metalloproteinase 13 (MMP13). Collectively, these findings indicate that Thel induced osteogenic properties by regulating RUNX2 and MMP13 expression, suggesting that Thel could be further developed to treat bone disorders.

The important factors in the pathogenesis of neurodegenerative disorders include oxidative stress and neuron-glia system inflammation. Vignae Radiatae Semen (VRS) exhibits antihypertensive, anticancer, anti-melanogenesis, hepatoprotective, and immunomodulatory properties. However, the neuroprotective effects and anti-neuroinflammatory activities of VRS ethanol extract (VRSE) remained unknown. Thus, this study aimed to investigate the neuroprotective and anti-inflammatory activities of VRSE against hydrogen peroxide (H2O2)-induced neuronal cell death in mouse hippocampal HT22 cells and lipopolysaccharide (LPS)-stimulated BV2 microglial activation, respectively. This study revealed that VRSE pretreatment had significantly prevented H2O2-induced neuronal cell death and attenuated reactive oxygen species generations in HT22 cells. Additionally, VRSE attenuated the apoptosis protein expression while increasing the anti-apoptotic protein expression. Further, VRSE showed significant inhibitory effects on LPS-induced pro-inflammatory cytokines in BV2 microglia. Moreover, VRSE pretreatment significantly activated the tropomyosin-related kinase receptor B/cAMP response element-binding protein, brain-derived neurotrophic factor and nuclear factor erythroid 2-related factor 2, and heme oxygenase-1 signaling pathways in HT22 cells exposed to H2O2 and inhibited the activation of the mitogen-activated protein kinase and nuclear factor-κB mechanism in BV2 cells stimulated with LPS. Therefore, VRSE exerts therapeutic potential against neurodegenerative diseases related to oxidative stress and pathological inflammatory responses.

Glutamate-induced neural toxicity in autophagic neuron death is partially mediated by increased oxidative stress. Therefore, reducing oxidative stress in the brain is critical for treating or preventing neurodegenerative diseases. Selaginella tamariscina is a traditional medicinal plant for treating gastrointestinal bleeding, hematuria, leucorrhea, inflammation, chronic hepatitis, gout, and hyperuricemia. We investigate the inhibitory effects of Selaginella tamariscina ethanol extract (STE) on neurotoxicity and autophagic cell death in glutamate-exposed HT22 mouse hippocampal cells. STE significantly increased cell viability and mitochondrial membrane potential and decreased the expression of reactive oxygen species, lactate dehydrogenase release, and cell apoptosis in glutamate-exposed HT22 cells. In addition, while glutamate induced the excessive activation of mitophagy, STE attenuated glutamate-induced light chain (LC) 3 II and Beclin-1 expression and increased p62 expression. Furthermore, STE strongly enhanced the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) phosphorylation activation. STE strongly inhibited glutamate-induced autophagy by activating the PI3K/Akt/mTOR signaling pathway. In contrast, the addition of LY294002, a PI3K/Akt inhibitor, remarkably suppressed cell viability and p-Akt and p62 expression, while markedly increasing the expression of LC3 II and Beclin-1. Our findings indicate that autophagy inhibition by activating PI3K/Akt/mTOR phosphorylation levels could be responsible for the neuroprotective effects of STE on glutamate neuronal damage.

Oxidative stress-mediated neuronal damage is associated with the pathogenesis and development of neurodegenerative diseases. Chrysanthemum indicum has antioxidant properties. However, the neuroprotective effects and the cellular mechanism of C. indicum ethanol extract (CIE) against oxidative damage in hippocampal neuronal cells have not been clearly elucidated. Therefore, this study investigated whether CIE has protective effects against hydrogen peroxide (H2O2)-induced oxidative toxicity in HT22 cells. CIE pretreatment significantly improved neuronal cell viability. Moreover, the formation of intracellular reactive oxygen species and apoptotic bodies, and mitochondrial depolarization were significantly reduced in HT22 cells with H2O2-induced oxidative toxicity. Furthermore, CIE increased the phosphorylation of tropomyosin-related kinase receptor B (TrkB), protein kinase B (Akt), cAMP response element-binding protein, the expression of brain-derived neurotrophic factor, antioxidant enzymes, and the nuclear translocation of nuclear factor erythroid 2-related factor 2 by activating the TrkB/Akt signaling pathway. In contrast, the addition of K252a, a TrkB inhibitor, or MK-2206, an Akt-selective inhibitor, reduced the neuroprotective and antioxidant effects of CIE. Taken together; CIE exhibits neuroprotective and antioxidant effects against oxidative damage. Therefore, it can be a potential agent for treating oxidative stress-related neurodegenerative diseases.

Forsythia Fruit (FF), the fruit of Forsythia suspensa, has been used since ancient times as an herbal medication in East Asia to treat inflammation, gonorrhea, and pharyngitis. However, the efficacy of FF against liver damage due to inflammation has not been studied. Here, we explored the protective effects of FF in a mouse hepatitis model induced by lipopolysaccharide (LPS)/D-galactosamine (GalN) treatment. We measured inflammatory cytokine and aminotransferase levels in mouse blood and analyzed the effects of FF on inflammatory gene and protein expression levels in liver tissue. Our results show that FF treatment effectively lowers inflammatory cytokine and serum aminotransferase levels in mice and inhibits the expression of hepatic cytokine mRNA and inflammatory proteins. Furthermore, treatment with FF activated the antioxidant pathway HO-1/Nrf-2 and suppressed severe histological alteration in the livers of LPS/D-GalN-treated mice. Further investigation of the effects of FF on inflammatory reactions in LPS-stimulated macrophages showed that pretreatment with FF inhibits inflammatory mediator secretion and activation of inflammatory mechanisms both in a mouse macrophage RAW 264.7 cells and in primary peritoneal macrophages. These results show that FF has potential worth as a candidate for the treatment of fulminant inflammatory reactions and subsequent liver injury.

This study aimed to determine the anti-inflammatory and hepatoprotective effects of Lysimachiae Herba ethanolic extract (LHE) in lipopolysaccharide (LPS)-stimulated macrophages and in a LPS/D-galactosamine (GalN)-induced acute hepatitis mouse model. Then, the production of inflammatory mediators and the activation of related pathways in macrophages were explored. Finally, we assessed the serum aminotransferase levels and the expression of inflammatory/antioxidant molecules in liver tissues in mice. Results revealed that LHE treatment significantly inhibited the production of inflammatory mediators in LPS-stimulated RAW 264.7 macrophages. Molecular data showed that LHE remarkably increased the activities of the antioxidant pathway and inhibited the phosphorylation of mitogen-activated protein kinase as well as the transcriptional activity of nuclear factor-κB induced by LPS. Furthermore, it prevented acute liver damage caused by LPS/D-GalN-induced hepatitis by inhibiting aminotransferase levels and histopathological changes in mice. Moreover, treatment with LHE significantly inhibited the activation of inflammatory pathways and increased the expression of antioxidant molecules including heme oxygenase-1/Nuclear factor erythroid 2-related factor 2. In conclusion, LHE has potent anti-inflammatory and hepatoprotective effects in LPS-stimulated macrophages and the LPS/D-GalN-induced acute hepatitis mouse model. Thus, it can be a treatment option for inflammation, hepatitis, and liver injury.

Hoveniae semen seu fructus (HSF, fruit and seed of Hovenia dulcis Thunb) is an important traditional herbal medicine and food supplement in East Asia for the treatment of liver diseases, alcohol poisoning, obesity, allergy, and cancer. HSF has also been reported to have anti-inflammatory activity, but the cellular mechanism of action is not fully understood. We assessed the anti-inflammatory properties of an HSF ethanol (HSFE) extract and explored its precise mechanism. The ability of HSFE to suppress inflammatory responses was investigated in a murine macrophage cell line, RAW 264.7, and mouse primary macrophages. Secretions of NO, proinflammatory cytokines, inflammatory factors, and related proteins were measured using the Griess assay, ELISA, Western blot analysis, and real-time PCR, respectively. In addition, the main components of HSFE were analyzed by HPLC, and their anti-inflammatory activity was confirmed. Our results showed that pretreatment of HSFE markedly reduced the expression of NO and iNOS without causing cytotoxicity and significantly attenuated secretion of proinflammatory cytokines, including TNF-α, IL-6, and IL-1β. In addition, HSFE strongly suppressed phosphorylation of MAPK and decreased the activation of AP-1, JAK2/STAT, and NF-κB in LPS-stimulated RAW 264.7 cells in a concentration-dependent manner. Furthermore, HSFE strongly suppressed the inflammatory cytokine levels in mouse peritoneal macrophages. Also, as a result of HPLC analysis, three main components, ampelopsin, taxifolin, and myricetin, were identified in the HSFE extract, and each compound effectively inhibited the secretion of inflammatory mediators induced by LPS. These findings show that HSFE exerts anti-inflammatory effects by suppressing the activation of MAPK, AP-1, JAK2/STAT, and NF-κB signaling pathways in LPS-stimulated macrophages. In addition, the anti-inflammatory efficacy of HSFE appears to be closely related to the action of the three main components. Therefore, HSFE appears to be a promising candidate for the treatment of inflammatory diseases.

Banhasasim-tang (BHS) is an herbal medicine that has been widely used in East Asia to treat various symptoms associated with upper abdomen swelling. BHS has not been studied previously for neuroinflammation or cognitive disorder. Here, we use a lipopolysaccharide (LPS) model to investigate the effects and mechanisms of BHS in neuroinflammation and cognitive impairment of mice. We used a mouse model of LPS-induced cognitive impairment and neuroinflammation and examined whether administration of BHS prevents these deficits via Morris water maze test, passive avoidance test, histopathological analysis, Western blotting, and real-time reverse transcription polymerase chain reaction (RT-qPCR). We found via behavioral tests that BHS treatment effectively prevented LPS-induced memory loss and neuronal damage in mice. Histopathological analysis of mouse brains revealed that BHS inhibited LPS-induced expression of microglial and astrocyte activation markers. Furthermore, BHS inhibits the production of markers related to neurodegeneration, amyloidogenesis, and inflammation, and mRNA expression of inflammatory mediators in mouse brain tissue. Additionally, BHS pretreatment effectively inhibited generation of inflammatory factors and pathways in BV2 microglial cells stimulated by LPS. These observations indicate that BHS is effective in preventing cognitive impairment caused by neuroinflammation and has strong potential as a candidate treatment for neuronal inflammatory diseases.

Pyeongwisan (PW) is an herbal medication used in traditional East Asian medicine to treat anorexia, abdominal distension, borborygmus and diarrhea caused by gastric catarrh, atony and dilatation. However, its effects on inflammation-related diseases are unknown. In this study, we investigated the biological effects of PW on lipopolysaccharide (LPS)-mediated inflammation in macrophages and on local inflammation in vivo. We investigated the biological effects of PW on the production of inflammatory mediators, pro-inflammatory cytokines and related products as well as the activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) in LPS-stimulated macrophages. Additionally, we evaluated the analgesic effect on the acetic acid-induced writhing response and the inhibitory activity on xylene-induced ear edema in mice. PW showed anti-inflammatory effects by inhibiting the production of nitric oxide (NO), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) and interleukin-1β (IL-1β). In addition, PW strongly suppressed inducible nitric oxide synthase (iNOS), a NO synthesis enzyme, induced heme oxygenase-1 (HO-1) expression and inhibited NF-κB activation and MAPK phosphorylation. Also, PW suppressed TNF-α, IL-6 and IL-1β cytokine production in LPS-stimulated peritoneal macrophage cells. Furthermore, PW showed an analgesic effect on the writhing response and an inhibitory effect on mice ear edema. We demonstrated the anti-inflammatory effects and inhibitory mechanism in macrophages as well as inhibitory activity of PW in vivo for the first time. Our results suggest the potential value of PW as an inflammatory therapeutic agent developed from a natural substance.

Palmultang (PM) is an herbal decoction that has been used to treat anorexia, anemia, general prostration, and weakness due to chronic illness since medieval times in Korea, China, and Japan. The present study focused on the inhibitory effects of PM on the production of inflammatory factors and on the activation of mechanisms in murine macrophages. PM suppressed the expression of nitric oxide (NO), inflammatory cytokines and inflammatory proteins by inhibiting nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK) signaling pathways and by inducing heme oxygenase (HO)-1 expression. Collectively, our results explain the anti-inflammatory effect and inhibitory mechanism of PM in macrophages stimulated with lipopolysaccharide (LPS).

Angelicae Gigantis Radix (AGR) has been widely used as a traditional medicine in East Asia. The effects of AGR on neuroinflammation have not previously been studied in detail. In the study presented here, we investigated the antineuroinflammatory properties of this herb and its mechanism of operation. The effects of AGR on neuroinflammation were studied by measuring the production of inflammatory factors and related enzymes, and analyzing the expression levels of proteins and genes involved its activity, in lipopolysaccharide (LPS)-stimulated BV2 microglia. We found that AGR pretreatment strongly inhibits the production of nitric oxide (NO), cytokines, and the enzymes inducible nitric oxide synthase (iNOS), and cyclooxygenase (COX)-2, and effectively induces the activation of heme oxygenase (HO)-1 and its regulator, nuclear factor erythroid 2-related factor 2 (Nrf-2). We also found that AGR effectively regulates the activation of nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK). We confirmed the antineuroinflammatory effects of the main constituents of the plant as identified by high-performance liquid chromatography (HPLC). Our results indicate that the neuroinflammation inhibitory activity of AGR occurs through inhibition of NF-κB and MAPK and activation of Nrf-2.

Microglial activation and the resulting neuroinflammation are associated with a variety of brain diseases, such as Alzheimer’s disease and Parkinson’s disease. Thus, the control of microglial activation is an important factor in the development of drugs that can treat or prevent inflammation-related neurodegenerative disorders. Atractylodis Rhizoma Alba (ARA) has been reported to exhibit antioxidant, gastroprotective, and anti-inflammatory effects. However, the effects of ARA ethanolic extract (ARAE) on microglia-mediated neuroinflammation have not been fully elucidated. In this work, we explored the anti-neuroinflammatory properties and underlying molecular mechanisms of ARAE in lipopolysaccharide (LPS)-stimulated microglial BV2 cells. Our results showed that ARAE significantly attenuates the production of nitric oxide (NO) and inflammatory cytokines induced by LPS. ARAE treatment also inhibited the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 without causing cytotoxicity. ARAE markedly attenuated the transcriptional activities of nuclear factor (NF)-κB and mitogen-activated protein kinases (MAPK) phosphorylation, and induced heme oxygenase (HO)-1 expression. High-performance liquid chromatography (HPLC) analysis showed that ARAE contains three main components—atractylenolide I, atractylenolide III, and atractylodin—all compounds that significantly inhibit the production of inflammatory factors. These findings indicate that ARAE may be a potential therapeutic agent for the treatment of inflammation-related neurodegenerative diseases.

Rhapontici Radix (RR) has been used in traditional medicine in East Asia and has been shown to have various beneficial effects. However, its biological properties or mechanism on inflammation-related diseases is unknown. The goal of this study was to determine the anti-inflammatory activity and underlying molecular mechanisms of Rhapontici Radix ethanol extract (RRE). The inhibitory effect of RRE on the production of NO, cytokines, inflammatory-related proteins, and mRNAs in LPS-stimulated macrophages was determined by the Griess assay, ELISA, Western blot analysis, and real-time RT-PCR, respectively. Our results indicate that treatment with RRE significantly inhibited the secretion of NO and inflammatory cytokines in RAW 264.7 cells and mouse peritoneal macrophages without cytotoxicity. We also found that RRE strongly suppressed the expression of iNOS and COX-2 and induced HO-1 expression. It also prevented nuclear translocation of NF-κB by inhibiting the phosphorylation and degradation of IκBα. Furthermore, the phosphorylation of MAPKs in LPS-stimulated RAW 264.7 cells was significantly inhibited by RRE. These findings suggest that RRE may operate as an effective anti-inflammatory agent by inhibiting the activation of NF-κB and MAPK signaling pathways and inducing HO-1 expression in macrophages. Our results suggest that RRE has potential value as candidate to inflammatory therapeutic phytomedicine.

The type I interferons (IFN-Is) are critical not only in early viral control but also in prolonged T-cell immune responses. However, chronic viral infections such as those of human immunodeficiency virus (HIV) and hepatitis C virus (HCV) in humans and lymphocytic choriomeningitis virus (LCMV) in mice overcome this early IFN-I barrier and induce viral persistence and exhaustion of T-cell function. Although various T-cell-intrinsic and -extrinsic factors are known to contribute to induction of chronic conditions, the roles of IFN-I negative regulators in chronic viral infections have been largely unexplored. Herein, we explored whether 2'-5' oligoadenylate synthetase-like 1 (OASL1), a recently defined IFN-I negative regulator, plays a key role in the virus-specific T-cell response and viral defense against chronic LCMV. To this end, we infected Oasl1 knockout and wild-type mice with LCMV CL-13 (a chronic virus) and monitored T-cell responses, serum cytokine levels, and viral titers. LCMV CL-13-infected Oasl1 KO mice displayed a sustained level of serum IFN-I, which was primarily produced by splenic plasmacytoid dendritic cells, during the very early phase of infection (2-3 days post-infection). Oasl1 deficiency also led to the accelerated elimination of viremia and induction of a functional antiviral CD8 T-cell response, which critically depended on IFN-I receptor signaling. Together, these results demonstrate that OASL1-mediated negative regulation of IFN-I production at an early phase of infection permits viral persistence and suppresses T-cell function, suggesting that IFN-I negative regulators, including OASL1, could be exciting new targets for preventing chronic viral infection.