Preconditioning of physiological cyclic stretch attenuated HMGB1 expression in pathologically mechanical stretch-activated A549 cells and ventilator-induced lung injury rats through inhibition of IL-6/STAT3/SOCS3

Downregulation of miR-26b attenuates early brain injury induced by subarachnoid hemorrhage via mediating the KLF4/STAT3/HMGB1 axis

BACKGROUND

Early brain injury (EBI) refers to early-onset secondary complications that occur after subarachnoid hemorrhage (SAH), and associated with high rate of disability and mortality. Recent investigations have indicated microRNA-26b (miR-26b) as a biomarker in the progression of SAH. Accordingly, the present study was designed to elucidate the role of miR-26b in influencing EBI following SAH and the downstream mechanisms.

METHODS

Firstly, SAH rat models and neuron injury models were developed to assess the effect of miR-26b on EBI-like symptoms and subsequent inflammation. Dual-luciferase reporter gene assay was further implemented to evaluate the binding of miR-26b to its putative target gene STAT3. Loss-of-function and rescue experiments were performed to assess the functionality of miR-26b-mediated STAT3 in both models.

RESULTS

miR-26b was found to target KLF4 and negative-modulate its expression, whereby aggravating EBI and inflammatory response in SAH rat models and stimulating hemoglobin-induced apoptosis in astrocytes. On the other hand, silencing of miR-26b reversed these changes in SAH rat models and hemoglobin (Hb)-induced astrocytes. miR-26b could further activate STAT3 via down-regulation of KLF4. Furthermore, KLF4 knockdown up-regulated HMGB1 to aggravate EBI following SAH.

CONCLUSIONS

Collectively, our findings highlighted the ameliorative effect of miR-26b inhibition on EBI in SAH and the possible mechanism associated with the KLF4/STAT3/HMGB1 axis.

miR‑223 ameliorates thalamus hemorrhage‑induced central poststroke pain via targeting NLRP3 in a mouse model

Central poststroke pain (CPSP) is a central neuropathic pain syndrome that occurs following a stroke and mainly manifests as pain and paresthesia in the body region corresponding to the brain injury area. At present, due to the lack of clinical attention given to CPSP, patients suffer from long-term pain that seriously affects their quality of life. Current literature indicates that microRNA (miR)-223 can impede inflammation and prevent collateral damage. The NLR family pyrin domain containing 3 (NLRP3) inflammasome induces IL-18 and IL-1β secretion and maturation and participates in the inflammatory response. Previous evidence has confirmed that miR-223 can negatively regulate NLRP3 in the development of inflammatory responses. However, whether the miR-223 targeting of NLRP3 is involved in CPSP remains unclear. In the present study, the expression of miR-223 was detected by reverse transcription-quantitative PCR analysis. The expression levels of NLRP3, caspase-1, ASC, IL-18, IL-1β, ERK1/2, p-ERK1/2 and GFAP were detected by western blot analysis. The results demonstrated that thalamic hemorrhagic stroke triggered by microinjection of collagenase Ⅳ (Coll IV) into the ventral posterior lateral (VPL) nucleus results in pain hypersensitivity. miR-223 expression level were significantly reduced in the CPSP model. The expression levels of NLRP3, caspase-1, ASC, IL-18 and IL-1β were significantly increased in the CPSP model. The expression level of GFAP was detected to determine astrocyte activation. The results demonstrated that astrocyte activation induced by Coll IV produced a CPSP model. The p-ERK1/2 expression level was demonstrated to be significantly increased in the CPSP model. The introduction of an miR-223 agomir significantly attenuated thalamic pain and significantly decreased the levels of NLRP3, caspase-1, ASC and proinflammatory cytokines (IL-18 and IL-1β). Furthermore, introducing a miR-223 antagomir into the VPL nucleus of naïve mice mimicked thalamic pain and significantly increased the levels of NLRP3, caspase-1, ASC and proinflammatory cytokine levels (IL-18 and IL-1β). These results indicated that miR-223 inhibited NLRP3 inflammasome activity (caspase-1, NLRP3 and ASC), which ameliorated thalamus hemorrhage-induced CPSP in mice via NLRP3 downregulation. In conclusion, these results may determine the mechanisms underlying CPSP and facilitate development of targeted therapy for CPSP.

Obesity Attenuates Ventilator-Induced Lung Injury by Modulating the STAT3-SOCS3 Pathway

Background

Ventilator-induced lung injury (VILI) is characterized by vascular barrier dysfunction and suppression of alveolar fluid clearance (AFC). Obesity itself leads to chronic inflammation, which may initiate an injurious cascade to the lungs and simultaneously induce a protective feedback. In this study, we investigated the protective mechanism of obesity on VILI in a mouse model.

Methods

The VILI model was set up via 6-h mechanical ventilation with a high tidal volume. Parameters including lung injury score, STAT3/NFκB pathway, and AFC were assessed. Mice with diet-induced obesity were obtained by allowing free access to a high-fat diet since the age of 3 weeks. After a 9-week diet intervention, these mice were sacrificed at the age of 12 weeks. The manipulation of SOCS3 protein was achieved by siRNA knockdown and pharmaceutical stimulation using hesperetin. WNK4 knockin and knockout obese mice were used to clarify the pathway of AFC modulation.

Results

Obesity itself attenuated VILI. Knockdown of SOCS3 in obese mice offset the protection against VILI afforded by obesity. Hesperetin stimulated SOCS3 upregulation in nonobese mice and provided protection against VILI. In obese mice, the WNK4 axis was upregulated at the baseline, but was significantly attenuated after VILI compared with nonobese mice. At the baseline, the manipulation of SOCS3 by siRNA and hesperetin also led to the corresponding alteration of WNK4, albeit to a lesser extent. After VILI, WNK4 expression correlated with STAT3/NFκB activation, regardless of SOCS3 status. Obese mice carrying WNK4 knockout had VILI with a severity similar to that of wild-type obese mice. The severity of VILI in WNK4-knockin obese mice was counteracted by obesity, similar to that of wild-type nonobese mice only.

Conclusions

Obesity protects lungs from VILI by upregulating SOCS3, thus suppressing the STAT3/NFκB inflammatory pathway and enhancing WNK4-related AFC. However, WNK4 activation is mainly from direct NFκB downstreaming, and less from SOCS3 upregulation. Moreover, JAK2-STAT3/NFκB signaling predominates the pathogenesis of VILI. Nevertheless, the interaction between SOCS3 and WNK4 in modulating VILI in obesity warrants further investigation.

Attenuation of ventilator-induced lung injury through suppressing the pro-inflammatory signaling pathways: A review on preclinical studies

Mechanical ventilation (MV) is a relatively common medical intervention in ICU patients. The main side effect of MV is the so-called "ventilator-induced lung injury" (VILI). The pathogenesis of VILI is not completely understood; however, it has been reported that MV might be associated with up-regulation of various inflammatory mediators within the lung tissue and that these mediators might act as pathogenic factors in lung tissue injury. One potential mechanism for the generation of inflammatory mediators is through the release of endogenous molecules known as damage associated molecular patterns (DAMPs). These molecules are released from injured tissues and can bind to pattern recognition receptors (PRRs). PRR activation generally leads to the production and release of inflammation-related molecules including innate immune cytokines and chemokines. It has been suggested that blocking DAMP/PRR signaling pathways might diminish the progression of VILI. Herein, we review the latest findings with regard to the effects of DAMP/PRRs and their blockade, as well as the potential therapeutic targets and future research directions in VILI. Results of studies performed on human samples, animal models of disease, as well as relevant in vitro systems will be discussed.

6-Gingerol attenuates ventilator-induced lung injury via anti-inflammation and antioxidative stress by modulating the PPARγ/NF-κBsignalling pathway in rats

Although mechanical ventilation (MV) is indispensable to life-support therapy in critically ill patients, it may promote or aggravatelunginjury known asventilator-inducedlunginjury(VILI). 6-Gingerol is the principal ingredient of ginger with potential anti-inflammatory and antioxidant properties in various diseases. Nevertheless, the role and mechanism of 6-gingerol in the process of VILI has not been explicitly investigated. In the study, we found that pre-treatment with 6-gingerol significantly improved the histological changes and pulmonary oedema, inhibited neutrophil accumulation and the release of early pro-inflammatory cytokines and MPO, and reduced oxidative stress reactions after high MV. Moreover, 6-gingerol treatment also increased PPARγ expression and decreased NF-κB activation in rats subjected to high MV. Furthermore, GW9662, a specific PPARγ inhibitor, was demonstrated to activatethe NF-κB pathway and cancele the protective role of 6-gingerol in VILI. This indicates that 6-gingerol exerted anti-inflammatory and antioxidative stress effects in VILI by activating PPARγ and inhibiting the NF-κBsignalling pathway.

SOCS3-microtubule interaction via CLIP-170 and CLASP2 is critical for modulation of endothelial inflammation and lung injury

Proinflammatory cytokines such as IL-6 induce endothelial cell (EC) barrier disruption and trigger an inflammatory response in part by activating the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway. The protein suppressor of cytokine signaling-3 (SOCS3) is a negative regulator of JAK-STAT, but its role in modulation of lung EC barrier dysfunction caused by bacterial pathogens has not been investigated. Using human lung ECs and EC-specific SOCS3 knockout mice, we tested the hypothesis that SOCS3 confers microtubule (MT)-mediated protection against endothelial dysfunction. SOCS3 knockdown in cultured ECs or EC-specific SOCS3 knockout in mice resulted in exacerbated lung injury characterized by increased permeability and inflammation in response to IL-6 or heat-killed Staphylococcus aureus (HKSA). Ectopic expression of SOCS3 attenuated HKSA-induced EC dysfunction, and this effect required assembled MTs. SOCS3 was enriched in the MT fractions, and treatment with HKSA disrupted SOCS3-MT association. We discovered that-in addition to its known partners gp130 and JAK2-SOCS3 interacts with MT plus-end binding proteins CLIP-170 and CLASP2 via its N-terminal domain. The resulting SOCS3-CLIP-170/CLASP2 complex was essential for maximal SOCS3 anti-inflammatory effects. Both IL-6 and HKSA promoted MT disassembly and disrupted SOCS3 interaction with CLIP-170 and CLASP2. Moreover, knockdown of CLIP-170 or CLASP2 impaired SOCS3-JAK2 interaction and abolished the anti-inflammatory effects of SOCS3. Together, these findings demonstrate for the first time an interaction between SOCS3 and CLIP-170/CLASP2 and reveal that this interaction is essential to the protective effects of SOCS3 in lung endothelium.

Inhibition of calcineurin/NFATc4 signaling attenuates ventilator‑induced lung injury

Ventilator-induced lung injury (VILI) is a life-threatening condition caused by the inappropriate use of mechanical ventilation (MV). However, the precise molecular mechanism inducing the development of VILI remains to be elucidated. In the present study, it was revealed that the calcineurin/NFATc4 signaling pathway mediates the expression of adhesion molecules and proinflammatory cytokines essential for the development of VILI. The present results revealed that a high tidal volume ventilation (HV) caused lung inflammation and edema in the alveolar walls and the infiltration of inflammatory cells. The calcineurin activity and protein expression in the lungs were increased in animals with VILI, and NFATc4 translocated into the nucleus following calcineurin activation. Furthermore, the translocation of NFATc4 and lung injury were prevented by a calcineurin inhibitor (CsA). Thus, the present results highlighted the critical role of the calcineurin/NFATc4 signaling pathway in VILI and suggest that this pathway coincides with the release of ICAM-1, VCAM-1, TNF-α and IL-1β.

Rev-erbα can regulate the NF-κB/NALP3 pathway to modulate lipopolysaccharide-induced acute lung injury and inflammation

Progressive lung injury and pulmonary inflammation can be induced by an intraperitoneal injection of lipopolysaccharide (LPS). Interleukin-1β (IL-1β) is a key pro-inflammatory cytokine that can further exaggerate inflammation, which is cleaved and activated by the NALP3 inflammasome. Although the nuclear receptor Rev-erbα attenuates the level of LPS-induced pulmonary inflammation, the mechanism remains unclear. In this study, we investigated the influence of LPS-induced production of IL-1β and Rev-erbα on the development of lung inflammation. Herein, we demonstrate that Rev-erbα reduces IL-1β production and lung injury following an intraperitoneal injection of LPS, which is dependent on the NF-κB/NALP3 pathway. Thus, Rev-erbα is able to decrease the extent of acute lung injury by regulating IL-1β production. This mechanism may represent a potential novel therapeutic approach for lung injury.

p38MAPK plays a pivotal role in the development of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening illness characterized by a complex pathophysiology, involving not only the respiratory system but also nonpulmonary distal organs. Although advances in the management of ARDS have led to a distinct improvement in ARDS-related mortality, ARDS is still a life-threatening respiratory condition with long-term consequences. A better understanding of the pathophysiology of this condition will allow us to create a personalized treatment strategy for improving clinical outcomes. In this article, we present a general overview p38 mitogen-activated protein kinase (p38MAPK) and recent advances in understanding its functions. We consider the potential of the pharmacological targeting of p38MAPK pathways to treat ARDS.

Preconditioning of physiological cyclic stretch inhibits the inflammatory response induced by pathologically mechanical stretch in alveolar epithelial cells

The aim of the present study was to investigate the effects of preconditioning of physiological cyclic stretch (CS) on the overexpression of early pro-inflammatory cytokines [including tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-8] during the inflammatory response induced by pathologically mechanical stretch in lung epithelial cells, and to determine its molecular mechanism of action. Cells were subjected to 5% CS for various durations (0, 15, 30, 60 and 120 min) prior to 6 h treatment with pathological 20% CS. In a separate experiment, cells were preconditioned with physiological 5% CS or incubated with a nuclear factor (NF)-κB inhibitor, pyrroldine dithiocarbamate (PDTC). The expression levels of inflammatory mediators were measured using reverse transcription-quantitative polymerase chain reaction. NF-κB was quantified using western blot analysis. Preconditioning with physiological 5% CS for 30, 60 and 120 min was demonstrated to significantly attenuate the release of pathologically mechanical stretch-induced early pro-inflammatory cytokines (TNF-α, IL-1β and IL-8) in alveolar epithelial cells (P<0.05) and significantly reduce the expression of NF-κB (P<0.05). Peak suppression was observed in cells preconditioned for 60 min. In the second set of experiments, it was demonstrated that mechanical stretch-induced release of TNF-α, IL-1β and IL-8 was significantly inhibited by both PDTC pretreatment and 5% CS pretreatment alone (all P<0.05). Furthermore, significant inhibition was also observed when both 5% CS pretreatment and PDTC pretreatment was used on mechanical stretch-induced cells (P<0.05), which was markedly greater than the inhibition induced by either pretreatment alone. The present findings suggest that preconditioning with physiological 5% CS is able to inhibit the inflammatory response induced by pathologically mechanical stretch in alveolar epithelial cells. These anti-inflammatory effects are induced, at least in part, by suppressing the NF-κB signaling pathway.

Association of serum HMGB2 level with MACE at 1 mo of myocardial infarction: Aggravation of myocardial ischemic injury in rats by HMGB2 via ROS

High-mobility group box (HMGB) family is related to inflammatory diseases. We investigated whether serum HMGB2 levels are related to myocardial infarction (MI) severity and major adverse cardiac events (MACE) during MI. We included 432 consecutive patients with ST-segment elevation myocardial infarction and 312 controls. Serum HMGB2 levels were significantly higher in MI patients than in controls. Increased HMGB2 levels were associated with MACE and negatively with ejection fraction in MI patients. HMGB2 was an independent determinant of MACE in logistic regression analysis. HMGB2 protein (10 μg) or saline was injected intramyocardially in MI rats, with or without coadministration of the NADPH oxidase inhibitor apocynin. After 72 h, pathological, echocardiographic, and hemodynamic examinations showed that HMGB2 increased infarct size and worsened cardiac function in MI rats. Moreover, HMGB2 administration enhanced reactive oxygen species (ROS) production, cell apoptosis, inflammation, and autophagosome clearance impairment, which were attenuated by coadministration of apocynin or knock down of receptor for advanced glycation end products (RAGE). In conclusion, increased serum HMGB2 levels are associated with MI severity and MACE at 1 mo. HMGB2 promotes myocardial ischemic injury in rats and hypoxic H9C2 cell damage via ROS provoked by RAGE.

NEW & NOTEWORTHY We demonstrate that serum high-mobility group box 2 is associated with major adverse cardiac events at 1 mo in myocardial infarction patients. Mechanistically, high-mobility group box 2 promotes reactive oxygen species production via receptor for advanced glycation end products signaling in ischemic myocardium, thereby aggravating cell apoptosis, inflammation, and autophagosome clearance impairment. This study reveals that high-mobility group box 2 is a novel factor enhancing ischemic injury in myocardial infarction.