Amino Sugar-Enriched Fraction of Korean Red Ginseng Extract Induces the Priming Step of NLRP3 Inflammasome.

Intracellular protein complexes, known as inflammasomes, activate caspase-1 and induce the secretion of pro-inflammatory cytokines, namely interleukin (IL)-1ß and -18. Korean Red Ginseng extract (RGE) is a known immunomodulator and a potential candidate for the regulation of inflammasomes. The saponins, such as ginsenosides, of RGE inhibit inflammasome signaling, while non-saponin substances containing amino sugars promote the priming step, up-regulating inflammasome components (pro-IL-1ß, NLRP3, caspase-1, and Asc). In this study, the amino sugar-enriched fraction (ASEF), which increases only non-saponin components, including amino sugars, without changing the concentration of saponin substances, was used to investigate whether saponin or non-saponin components of RGE would have a greater impact on the priming step. When murine macrophages were treated with ASEF, the gene expression of inflammatory cytokines (IL-1α, TNFα, IL-6, and IL-10) increased. Additionally, ASEF induced the priming step but did not affect the inflammasome activation step, such as the secretion of IL-1ß, cleavage of caspase-1, and formation of Asc pyroptosome. Furthermore, the upregulation of gene expression of inflammasome components by ASEF was blocked by inhibitors of Toll-like receptor 4 signaling. Maltol, the main constituent of ASEF, promoted the priming step but inhibited the activation step of the inflammasome, while arginine, sugars, arginine-fructose-glucose, and fructose-arginine, the other main constituents of ASEF, had no effect on either step. Thus, certain amino sugars in RGE, excluding maltol, are believed to be the components that induce the priming step. The priming step that prepares the NLRP3 inflammasome for activation appears to be induced by amino sugars in RGE, thereby contributing to the immune-boosting effects of RGE.

Sonic vibration ameliorates inflammatory diseases via the up-regulation of IL-10.

Sonic vibration (SV), or vibroacoustic therapy, is applied to enhance local and systemic blood circulation and alleviate pain using low-frequency sine wave vibrations. However, there is limited scientific data on the mechanisms through which the benefits are achieved. In this study, we investigated the impact of SV on inflammatory responses by assessing cytokine secretion in both in vivo and in vitro models. After inducing inflammatory responses in mice and macrophages, we studied cytokine expression and the symptoms of inflammatory diseases in response to three frequencies (14, 45, or 90 Hz) of SV stimulation at 0.5 m/s2 of amplitude. The results showed that SV at 90 Hz significantly increased interelukin-10 (IL-10) secretion in mice who were administered lipopolysaccharides (LPS) and increased the expression of IL-10 transcripts in peritoneal exudate cells and macrophages. Furthermore, SV at 90 Hz improved LPS-induced lethality and alleviated symptoms in a colitis model. In conclusion, this study scientifically proves the anti-inflammatory effects of vibration therapy through its ability to increase IL-10 expression.

Characterization of Inflammasomes and Their Regulation in the Red Fox.

BACKGROUND: Inflammasomes recognize endogenous and exogenous danger signals, and subsequently induce the secretion of IL-1ß. Studying inflammasomes in the red fox (Vulpes vulpes) is crucial for wildlife veterinary medicine, as it can help control inflammatory diseases in foxes. METHODS: We investigated the activation and intracellular mechanisms of three inflammasomes (NLRP3, AIM2, and NLRC4) in fox peripheral blood mononuclear cells (PBMCs), using established triggers and inhibitors derived from humans and mice. RESULTS: Fox PBMCs exhibited normal activation and induction of IL-1ß secretion in response to representative inflammasome triggers (ATP and nigericin for NLRP3, dsDNA for AIM2, flagellin for NLRC4). Additionally, PBMCs showed normal IL-1ß secretion when inoculated with inflammasome-activating bacteria. In inhibitors of the inflammasome signaling pathway, fox inflammasome activation was compared with mouse inflammasomes. MCC950, a selective NLRP3 inhibitor, suppressed the secretion of dsDNA- and flagellin-mediated IL-1ß in foxes, unlike mice. CONCLUSIONS: These findings suggest that NLRP3 may have a common role in dsDNA- and flagellin-mediated inflammasome activation in the red fox. It implies that this fox inflammasome biology can be applied to the treatment of inflammasome-mediated diseases in the red fox.

The Role of NLRP3 Inflammasomes in Trained Immunity.

Inflammasomes are cytosolic multi-protein complexes that play an important role in the innate immune system, inducing cytokine maturation and pyroptosis. Trained immunity is the induction of memory in innate immune cells by epigenetic reprogramming due to repeated inflammatory stimuli that alter the inflammatory response and increase resistance to infection or disease. Although it is speculated that nucleotide-binding oligomerization domain (NOD), leucine-rich repeat (LRR), and the NLR family pyrin domain containing 3 (NLRP3) inflammasomes respond to various inflammatory stimuli and are associated with trained immunity, the exact relationship is still unclear. This paper aims to introduce data from recent research on the role of inflammasomes in trained immunity through cellular immunometabolic and epigenetic reprogramming. It also suggests a new therapeutic strategy for inflammatory diseases through the complementary regulation of inflammasomes and trained immunity.

JC2-11, a benzylideneacetophenone derivative, attenuates inflammasome activation.

Dysregulation of inflammasome activation induces chronic and excess inflammation resulting in several disorders, such as metabolic disorders and cancers. Thus, screening for its regulator derived from natural materials has been conducted progressively. JC2-11 (JC) was designed to enhance the antioxidant activity based on a chalcone, which is abundant in edible plants and a precursor of flavonoids. This study examined the effects of JC on inflammasome activation in human and murine macrophages. JC inhibited the secretion of interleukin (IL)-1ß and lactate dehydrogenases, and the cleavage of caspase-1 and gasdermin D in response to the tested activators (i.e., NLRP3, NLRC4, AIM2, and non-canonical inflammasome triggers). In addition, JC attenuated IL-1ß secretion from lipopolysaccharide (LPS)-injected mice, an inflammasome-mediating disease model. Mechanistically, JC blocked the expression of the inflammasome components during the priming step of the inflammasome, and interrupted the production of mitochondrial reactive oxygen species. In addition, JC inhibited the activity of caspase-1. In conclusion, JC may be a candidate pan-inflammasome inhibitor.

Maltol, a Natural Flavor Enhancer, Inhibits NLRP3 and Non-Canonical Inflammasome Activation.

Maltol (3-hydroxy-2-methyl-4-pyrone) is used widely as a food and cosmetic supplement, and it has antioxidant and anti-inflammatory activities. Inflammasome causes the maturation and secretion of interleukin (IL)-1ß and -18 through the activation of caspase-1 (Casp1), which contributes to various inflammatory diseases. This study examined the effects of maltol on the inflammasome activation in macrophages and mice. Lipopolysaccharide (LPS)-primed macrophages were treated with a trigger of NLRP3, NLRC4, AIM2, or non-canonical (NC) inflammasomes in the presence of maltol. The secretion of IL-1ß and IL-18 and the cleavage of Casp1 were analyzed as indices of inflammasome activation. Mice were injected with LPS and an NLRP3 trigger with or without maltol, and the peritoneal IL-1ß secretions were observed. The effects of maltol on reactive oxygen species (ROS) production and Casp1 activity were analyzed to determine the mechanism. Maltol inhibited the activation of NLRP3 and NC inflammasomes, but it did not alter the other inflammasomes. Maltol also attenuated IL-1ß secretion resulting from the inflammasome activation in mice. The anti-inflammatory mechanism of maltol was revealed by the inhibition of ROS production and Casp1 activity. Maltol is suggested to be promising as a anti-inflammasome molecule.

Parabens disrupt non-canonical inflammasome activation.

Parabens are synthetic chemicals widely used as preservatives in cosmetics, pharmaceuticals, and foods. Although parabens, i.e., ethyl- and methyl-parabens, are considered relatively safe, study of possible health hazards has been undertaken due to the frequent exposure to parabens and their accumulation in the body. In this study, we elucidated the effect of parabens on inflammasome induction of inflammatory responses in innate immunity, such as interleukin (IL)-1ß maturation and gasdermin D (GSDMD)-mediating pyroptosis. Parabens attenuated the inflammatory responses to intracellular lipopolysaccharide (LPS) triggering of non-canonical (NC) inflammasome activation, but did not alter canonical inflammasome (i.e., NLRP3, NLRC4 and AIM2) responses. The NC inflammasome is assembled by the interaction of murine caspase (Casp)-11 (Casp4/5 in human) with cytosolic LPS, inducing endotoxin sepsis. Parabens selectively inhibited NC inflammasome activation in both human and murine macrophages and diminished the peritoneal IL-1ß production in LPS-injected mice. Parabens blocked the cleavage of GSDMD, Casp1, and Casp4, but did not change the expression of Casp11 or the activity of Casp1. Taken together, the results indicate that parabens could disrupt Gram-negative pathogen infection through the inhibition of NC inflammasome activation.

NLRP3 Triggers Attenuate Lipocalin-2 Expression Independent with Inflammasome Activation.

Lipocalin-2 (LCN2), a small secretory glycoprotein, is upregulated by toll-like receptor (TLR) signaling in various cells and tissues. LCN2 inhibits bacterial growth by iron sequestration and regulates the innate immune system. Inflammasome activates the inflammatory caspases leading to pyroptosis and cytokine maturation. This study examined the effects of inflammasome activation on LCN2 secretion in response to TLR signaling. The triggers of NLRP3 inflammasome activation attenuated LCN2 secretion while it induced interleukin-1ß in mouse macrophages. In mice, NLRP3 inflammasome activation inhibited TLR-mediated LCN2 secretion. The inhibition of NLRP3 triggers on LCN2 secretion was caused by the inhibited transcription and translation of LCN2. At the same time, no changes in the other cytokines and IκBζ, a well-known transcriptional factor of Lcn2 transcription, were observed. Overall, NLRP3 triggers are a regulator of LCN2 expression suggesting a new linkage of inflammasome activation and LCN2 secretion in the innate immunity.

Lower Temperatures Exacerbate NLRP3 Inflammasome Activation by Promoting Monosodium Urate Crystallization, Causing Gout.

Gout is a recurrent and chronic form of arthritis caused by the deposition of monosodium urate (MSU) crystals in the joints. Macrophages intake MSU crystals, the trigger for NLRP3 inflammasome activation, which leads to the release of interleukin (IL)-1ß and results in the flaring of gout. The effects of temperature, an environmental factor for MSU crystallization, on IL-1ß secretion have not been well studied. This study examined the effects of temperature on inflammasome activation. Specific triggers activated canonical inflammasomes (NLRP3, NLRC4, and AIM2) in murine macrophages at various temperatures (25, 33, 37, 39, and 42 °C). The maturation of IL-1ß and caspase-1 was measured as an indicator for inflammasome activation. As expected, the optimal temperature of inflammasome activation was 37 °C. The MSU crystal-mediated activation of inflammasome increased at temperatures lower than 37 °C and decreased at higher temperatures. MSU crystals at lower temperatures enhanced IL-1ß secretion via the NLRP3 inflammasome pathway. A lower temperature promoted the formation of MSU crystals without changing phagocytosis. Overall, lower temperatures form more MSU crystals and enhance NLRP3 inflammasome activation. In light of these findings, it is possible that hyperthermia therapy may reduce gout flaring.

Korean Red Ginseng attenuates ultraviolet-mediated inflammasome activation in keratinocytes.

BACKGROUND: Keratinocytes form a physical barrier and act as an innate immune cell in skin. Keratinocytes secrete pro-inflammatory cytokines, such as interleukin (IL)-1ß, resulting from inflammasome activation when exposed to ultraviolet (UV) irradiation. Korean Red Ginseng extracts (RGE) have been well-studied as modulators of inflammasome activation in immune cells, such as macrophages. In the study, we elucidated the role of RGE on the UV-mediated inflammasome activation in keratinocytes compared with that in macrophages. METHODS: Human skin keratinocyte cells (HaCaT), human epidermal keratinocytes (HEK), human monocyte-like cells (THP-1), and mouse macrophages were treated with RGE or a saponin fraction (SF) or non-saponin fraction (NS) of RGE before and after UV irradiation. The secretion levels of IL-1ß, as an indicator of inflammasome activation, were analyzed. RESULTS: The treatment of RGE or SF in macrophages after UV irradiation inhibited IL-1ß secretion, but similar treatment in HaCaT cells did not. However, the treatment of RGE or SF in HaCaT cells in the presence of poly I:C, a toll-like receptor (TLR) 3 ligand, before UV exposure elicited the inhibition of the IL-1ß secretion. The inhibition was caused by the disruption by RGE or SF of the TLR mediating up-regulation of the pro-IL-1ß and NLRP3 genes during the priming step. CONCLUSION: RGE and its saponins inhibit IL-1ß secretion in response to UV exposure in both keratinocytes and macrophages. In particular, RGE treatment interrupted only the priming step in keratinocytes, although it did attenuate both the priming and activation steps in macrophages.

Fructose-arginine, a non-saponin molecule of Korean Red Ginseng, attenuates AIM2 inflammasome activation.

BACKGROUND: Korean Red Ginseng extract (RGE) has been reported to act as an inflammasome modulator. Ginsenosides, saponin molecules of RGE, selectively inhibit activation of NLRP3 and AIM2 inflammasomes, while non-saponin molecules of RGE upregulate inflammasome components associated with the initiation of NLRP3 inflammasome activation. In this study, we investigated the effect of non-saponin components of RGE on AIM2 inflammasome activation. METHODS: The role of non-saponins of RGE on AIM2 inflammasomes was tested in mouse bone marrow-derived macrophages, a human monocyte-like cell line, and a mouse animal model. Cells or mice were transfected with dsDNA or inoculated with Listeria monocytogenes to activate AIM2 inflammasomes. Several indices of inflammasome activation were examined via immunoblot or ELISA analysis. RESULTS: The non-saponin fraction and saponin-eliminating fraction (SEF) of RGE selectively attenuated the activation of AIM2 inflammasomes, but not that of NLRP3 or NLRC4 inflammasomes. Fructose-arginine, an amino-sugar, was shown to be effective against AIM2 inflammasome activation. CONCLUSION: Non-saponins of RGE, such as fructose-arginine, might be effective in regulating infectious and autoimmune diseases resulting from AIM2 inflammasome activation.

Riboflavin, vitamin B2, attenuates NLRP3, NLRC4, AIM2, and non-canonical inflammasomes by the inhibition of caspase-1 activity.

Riboflavin is commonly taken as a nutritional supplement, and it converts to coenzymes during the process of energy production from carbohydrates, fats, and proteins. Although riboflavin is considered to be an anti-inflammatory vitamin because of its antioxidant properties, the effects of riboflavin on inflammasome have been not reported. Inflammasome, a cytosolic surveillance protein complex, leads to the activation of caspase-1, cytokine maturation, and pyroptosis. In the present study, riboflavin attenuated the indicators of NLRP3 inflammasome activation in macrophages, such as the maturation and secretion of interleukin (IL)-1ß, IL-18, and caspase-1; the formation of Asc pyroptosome; and the cleavage of gasdermin D. In addition, the oral and peritoneal administration of riboflavin inhibited the peritoneal production of IL-1ß and IL-18 in a mouse model. Mechanistically, riboflavin prevented mitochondrial perturbations, such as mitochondrial ROS production and mitochondrial DNA release, which trigger the NLRP3 inflammasome assembly. Riboflavin was further confirmed to disrupt the activity of caspase-1, and it also inhibited the AIM2, NLRC4, and non-canonical inflammasomes. Therefore, riboflavin has both an antioxidant effect and an anti-inflammasome property that regulates the inflammatory response.

Characterization of equine inflammasomes and their regulation.

Inflammasome, a cytosolic multi-protein complex, assembly is a response to sensing intracellular pathogenic and endogenic danger signals followed by caspase-1 activation, which maturates precursor cytokines such as interleukin (IL)-1ß. Most inflammasome research has been undertaken in humans and rodents, and inflammasomes in veterinary species have not been well-characterized. In this study, we observed the effects of well-known inflammasome activators on equine peripheral blood monocytes (PBMCs). The NLRP3 inflammasome triggers include ATP, nigericin, aluminum crystals, and monosodium urate crystals, and NLRP3 activation induces IL-1ß secretion in a dose-dependent manner. Activators of NLRC4 and AIM2 inflammasomes include cytosolic flagellin and dsDNA, and their activation induces IL-1ß secretion. The bacterial inflammasome triggers Salmonella Typhimurium and Listeria monocytogenes also induce IL-ß releases. To elucidate the role of potassium efflux as an upstream signal of NLRP3 inflammasome activation, equine PBMCs were treated with blockers of potassium efflux in the presence of NLRP3 triggers. As a result, the IL-1ß secretion stemming from equine NLRP3 inflammasome activation was not completely attenuated by the inhibition of potassium efflux. Taken together, the results indicate that equine PBMCs normally secrete IL-1ß in response to well-known inflammasome activators, although equine NLRP3 inflammasome activation might not be dependent on potassium efflux.

IκBζ controls NLRP3 inflammasome activation via upregulation of the Nlrp3 gene.

Inflammasome activation induces the maturation and secretion of interleukin (IL)-1ß and -18, and is dependent on NF-κB signaling to induce the transcription of the inflammasome components, called the priming step. This study elucidated the role of IκBζ, an atypical IκBs (inhibitor of κB) and a coactivator of NF-κB target genes, on the activation of inflammasome. Bone marrow-derived macrophages (BMDMs) that originated from IκBζ-encoding Nfkbiz gene depletion mice presented a defect in NLRP3 inflammasome activation. In addition, the Nfkbiz+/- and Nfkbiz-/- mice significantly attenuated serum IL-1ß secretion in response to a monosodium urate injection, a NLRP3 trigger, when compared with Nfkbiz-+/+ mice. The lack of IκBζ in BMDMs produced a disability in the expression of Nlrp3 and pro-Il1ß mRNAs during the priming step. In addition, ectopic IκBζ expression enhanced the Nlrp3 promoter activity, and Nlrp3 and pro-Il1ß transcription. Overall, IκBζ controlled the activation of NLRP3 inflammasome by upregulating the Nlrp3 gene during the priming step.

Obovatol inhibits NLRP3, AIM2, and non-canonical inflammasome activation.

BACKGROUND: Obovatol, a biphenolic chemical originating from Magnolia obovata, has been utilized as a traditional medicine for the treatment of inflammatory diseases. Inflammasome induces maturation of inflammatory cytokines in response to intracellular danger signals, and its dysregulation induces inflammatory diseases. PURPOSE: The effect of obovatol on inflammasome activation has not been reported, although its anti-inflammatory properties have been studied. STUDY DESIGN/METHODS: Obovatol was treated to macrophages with inflammasome triggers, and secretions of interleukin (IL)-1ß, IL-18, and caspase-1 were measured as readouts of inflammasome activation. In addition, Asc pyroptosome formation, caspase-1 activity, and mitochondrial reactive oxygen species (ROS) production were analyzed in mechanical studies. Anti-inflammasome properties of obovatol were confirmed in an animal model. RESULTS: Obovatol inhibited NLRP3, AIM2, and non-canonical inflammasomes through inhibition of Asc pyroptosome formation and mitochondrial ROS generation. In addition, obovatol disrupted the priming step of inflammasome activation and inhibited transcription of inflammatory cytokines. In mice, obovatol attenuated serum IL-1ß elevation in response to monosodium urate crystals. CONCLUSION: Obovatol is suggested as an inhibitor of NLRP3, AIM2, and non-canonical inflammasomes.

Nonsaponin fraction of Korean Red Ginseng attenuates cytokine production via inhibition of TLR4 expression.

BACKGROUND: Ginsenosides of Korean Red Ginseng extracts (RGE) and its saponin components suppress secretion of inflammasome-mediating cytokines, whereas the nonsaponin fraction (NS) of RGE oppositely stimulates cytokine secretion. Although direct exposure of NS to macrophages in mice induces cytokine production, oral administration of NS has not been studied in inflammasome-related disease in animal models. METHODS: Mice were fed RGE or NS for 7 days and then developed peritonitis. Peritoneal cytokines were measured, and peritoneal exudate cells (PECs) were collected to assay expression levels of a set of toll-like receptors (TLRs) and cytokines in response to NS ingestion. In addition, the role of intestinal bacteria in NS-fed mice was assessed. The effect of preexposure to NS in bone marrow-derived macrophages (BMDMs) on cytokine production was further confirmed. RESULTS: NS ingestion attenuated secretion of peritoneal cytokines resulting from peritonitis. In addition, the isolated PECs from NS-fed mice presented lower TLR transcription levels than PECs from control diet-fed mice. BMDMs treated with NS showed downregulation of TLR4 mRNA and protein expression, which was mediated by the TLR4-MyD88-NFκB signal pathway. BMDMs pretreated with NS produced less cytokines in response to TLR4 ligands. CONCLUSION: NS administration directly inhibits TLR4 expression in inflammatory cells such as macrophages, thereby reducing secretion of cytokines during peritonitis.

Role of inflammasome regulation on immune modulators.

Inflammatory responses are essential in eliminating harmful substrates from damaged tissue and inducing recovery. Several cytokines participate in and facilitate this response. Certain cytokines such as interleukin (IL)-1ß and IL-18 are initially produced in precursor form in response to toll-like receptor (TLR) ligands and undergo maturation by inflammasomes, which are cytosolic multi-protein complexes containing nucleotide-binding oligomerization domain (NOD)-containing protein 2-like receptors (NLRs). Immune modulators targeting inflammasomes have been investigated to control inflammatory diseases such as metabolic syndrome. However, most immune modulators possessing anti-inflammasome properties attenuate production of other cytokines, which are essential for host defense. In this review, we analyzed the effect of anti-inflammasome agents on the production of cytokines which are not regulated by inflammasome and involving in initial immune responses. As a result, the inflammasome inhibitors are put into three categories: non-effector, stimulator, or inhibitor of cytokine production. Even the stimulator of cytokine production ameliorated symptoms resulting from inflammasome activation in mouse models. Thus, we suggest ideal immune modulators targeting inflammasomes in order to enhance cytokine production while inhibiting cytokine maturation.

Mercury and arsenic attenuate canonical and non-canonical NLRP3 inflammasome activation.

Exposure to heavy metals can cause several diseases associated with the immune system. Although the effects of heavy metals on production of inflammatory cytokines have been previously studied, the role of heavy metals in inflammasome activation remains poorly studied. The inflammasome is an intracellular multi-protein complex that detects intracellular danger signals, resulting in inflammatory responses such as cytokine maturation and pyroptosis. In this study, we elucidated the effects of four heavy metals, including cadmium (Cd), mercury (Hg), arsenic (As), and lead (Pb), on the activation of NLRP3, NLRC4, and AIM2 inflammasomes. In our results, mercury and arsenic inhibited interleukin (IL)-1ß and IL-18 secretion resulting from canonical and non-canonical NLRP3 inflammasome activation in macrophages and attenuated elevation of serum IL-1ß in response to LPS treatment in mice. In the mechanical studies, mercury interrupted production of mitochondrial reactive oxygen species, release of mitochondrial DNA, and activity of recombinant caspase-1, whereas arsenic down-regulated expression of promyelocytic leukemia protein. Both mercury and arsenic inhibited Asc pyroptosome formation and gasdermin D cleavage. Thus, we suggest that exposure to mercury and/or arsenic could disrupt inflammasome-mediated inflammatory responses, which might cause unexpected side effects.

Triggers of NLRC4 and AIM2 inflammasomes induce porcine IL-1ß secretion.

Pigs are an important livestock and serve as a large animal model due to physiological and anatomical similarities with humans. Thus, components of the porcine immune system such as inflammasomes need to be characterized for disease control, vaccination, and translational research purposes. Previously, we and others elucidated porcine nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family Pyrin domain containing 3 (NLRP3) inflammasome activation. However, until now, porcine NLR family caspase recruitment domain (CARD)-containing 4 (NLRC4) and absent in melanoma 2 (AIM2) inflammasomes have been not well studied. In this study, we treated well defined NLRC4 and AIM2 inflammasome triggers to porcine peripheral blood mononuclear cells (PBMCs) and murine bone-marrow derived macrophages (BMDMs) and observed interleukin (IL)-1ß maturation as a readout of inflammasome activation. NLRC4 (flagellin) and AIM2 (dsDNA) triggers led to IL-1ß secretion in both porcine PBMCs and mice macrophages. In addition, porcine and mouse NLRC4 and AIM2 inflammasomes responded differently to NLRP3 inhibitors. Bacterial inflammasome triggers, Salmonella enterica serovar Typhimurium, Listeria monocytogenes, and Escherichia coli, also induced IL-1ß secretion in porcine PBMCs. Taken together, we suggest that known triggers of NLRC4 and AIM2 inflammasomes in mice induce IL-1ß secretion in porcine PBMCs.

Antiviral and anti-inflammatory activity of budesonide against human rhinovirus infection mediated via autophagy activation.

Human rhinovirus (HRV) infection causes more than 80% of all common colds and is associated with severe complications in patients with asthma and chronic obstructive pulmonary disease. To identify antiviral drug against HRV infection, we screened 800 FDA-approved drugs and found budesonide as one of the possible drug candidates. Budesonide is a corticosteroid, which is commonly used to prevent exacerbation of asthma and symptoms of common cold. Budesonide specifically protects host cells from cytotoxicity following HRV infection, which depend on the expression of glucocorticoid receptor. Intranasal administration of budesonide lowered the pulmonary HRV load and the levels of IL-1ß cytokine leading to decreased lung inflammation. Budesonide regulates IL-1ß production following HRV infection independent of inflammasome activation. Instead, budesonide induces mitochondrial reactive oxygen species followed by activation of autophagy. Further, the inhibition of autophagy following chloroquine or bafilomycin A1 treatment reduced the anti-viral effect of budesonide against HRV, suggesting that the antiviral activity of budesonide was mediated via autophagy. The results suggest that budesonide represents a promising antiviral and anti-inflammatory drug candidate for the treatment of human rhinovirus infection.