Inhibition of Acute Lung Injury by TNFR-Fc through Regulation of an Inflammation-Oxidative Stress Pathway

Inhibition of S100A9 alleviates neurogenic pulmonary edema after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Neurogenic pulmonary edema (NPE) frequently arises as a complication subsequent to subarachnoid hemorrhage (SAH). Heterodimers of S100A8 and S100A9 are commonly formed, thereby initiating an inflammatory reaction through receptor binding on the cell surface. Paquinimod serves as a specific inhibitor of S100A9. The objective of this investigation is to assess the impact of Paquinimod administration and S100A9 knockout on NPE following SAH.

METHODS

In this study, SAH models of C57BL/6J wild-type (WT) and S100A9 knockout mice were established through intravascular perforation. These models were then divided into several groups, including the WT-sham group, S100A9-KO-sham group, WT-SAH group, WT-SAH + Paquinimod group, and S100A9-KO-SAH group. After 24 h of SAH induction, pulmonary edema was assessed using the lung wet-dry weight method and Hematoxylin and eosin (HE) staining. Additionally, the expression levels of various proteins, such as interleukin-1β (IL-1β), tumor necrosis factor α (TNF-α), occludin, claudin-3, Bax, Bcl-2, TLR4, MYD88, and pNF-κB, in lung tissue were analyzed using western blot and immunofluorescence staining. Lung tissue apoptosis was detected by TUNEL staining.

RESULTS

Firstly, our findings indicate that the knockout of S100A9 has a protective effect on early brain injury following subarachnoid hemorrhage (SAH). Additionally, the reduction of brain injury after SAH can also alleviate neurogenic pulmonary edema (NPE). Immunofluorescence staining and western blot analysis revealed that compared to SAH mice with wild-type S100A9 expression (WT-SAH), the lungs of S100A9 knockout SAH mice (S100A9-KO-SAH) and mice treated with Paquinimod exhibited decreased levels of inflammatory molecules (IL-1β and TNF-α) and increased levels of tight junction proteins. Furthermore, the knockout of S100A9 resulted in upregulated expression of the apoptotic-associated protein Bax and down-regulated expression of Bcl-2. Furthermore, a decrease in TLR4, MYD88, and phosphorylated pNF-κB was noted in S100A9-KO-SAH and Paquinimod treated mice, indicating the potential involvement of the TLR4/MYD88/NF-κB signaling pathway in the inhibition of the protective effect of S100A9 on NPE following SAH.

CONCLUSION

The knockout of S100A9 not only ameliorated initial cerebral injury following subarachnoid hemorrhage (SAH), but also mitigated SAH-associated neurogenic pulmonary edema (NPE). Additionally, Paquinimod was found to diminish NPE. These findings imply a correlation between the central nervous system and peripheral organs, highlighting the potential of safeguarding the brain to mitigate harm to peripheral organs.

Targeted Delivery of the Pan-Inflammasome Inhibitor MM01 as an Alternative Approach to Acute Lung Injury Therapy

Acute lung injury (ALI) is a severe pulmonary disorder responsible for high percentage of mortality and morbidity in intensive care unit patients. Current treatments are ineffective, so the development of efficient and specific therapies is an unmet medical need. The activation of NLPR3 inflammasome during ALI produces the release of proinflammatory factors and pyroptosis, a proinflammatory form of cell death that contributes to lung damage spreading. Herein, it is demonstrated that modulating inflammasome activation through inhibition of ASC oligomerization by the recently described MM01 compound can be an alternative pharmacotherapy against ALI. Besides, the added efficacy of using a drug delivery nanosystem designed to target the inflamed lungs is determined. The MM01 drug is incorporated into mesoporous silica nanoparticles capped with a peptide (TNFR-MM01-MSNs) to target tumor necrosis factor receptor-1 (TNFR-1) to proinflammatory macrophages. The prepared nanoparticles can deliver the cargo in a controlled manner after the preferential uptake by proinflammatory macrophages and exhibit anti-inflammatory activity. Finally, the therapeutic effect of MM01 free or nanoparticulated to inhibit inflammatory response and lung injury is successfully demonstrated in lipopolysaccharide-mouse model of ALI. The results suggest the potential of pan-inflammasome inhibitors as candidates for ALI therapy and the use of nanoparticles for targeted lung delivery.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Dichotomous Role of Tumor Necrosis Factor in Pulmonary Barrier Function and Alveolar Fluid Clearance

Alveolar-capillary leak is a hallmark of the acute respiratory distress syndrome (ARDS), a potentially lethal complication of severe sepsis, trauma and pneumonia, including COVID-19. Apart from barrier dysfunction, ARDS is characterized by hyper-inflammation and impaired alveolar fluid clearance (AFC), which foster the development of pulmonary permeability edema and hamper gas exchange. Tumor Necrosis Factor (TNF) is an evolutionarily conserved pleiotropic cytokine, involved in host immune defense against pathogens and cancer. TNF exists in both membrane-bound and soluble form and its mainly -but not exclusively- pro-inflammatory and cytolytic actions are mediated by partially overlapping TNFR1 and TNFR2 binding sites situated at the interface between neighboring subunits in the homo-trimer. Whereas TNFR1 signaling can mediate hyper-inflammation and impaired barrier function and AFC in the lungs, ligand stimulation of TNFR2 can protect from ventilation-induced lung injury. Spatially distinct from the TNFR binding sites, TNF harbors within its structure a lectin-like domain that rather protects lung function in ARDS. The lectin-like domain of TNF -mimicked by the 17 residue TIP peptide- represents a physiological mediator of alveolar-capillary barrier protection. and increases AFC in both hydrostatic and permeability pulmonary edema animal models. The TIP peptide directly activates the epithelial sodium channel (ENaC) -a key mediator of fluid and blood pressure control- upon binding to its α subunit, which is also a part of the non-selective cation channel (NSC). Activity of the lectin-like domain of TNF is preserved in complexes between TNF and its soluble TNFRs and can be physiologically relevant in pneumonia. Antibody- and soluble TNFR-based therapeutic strategies show considerable success in diseases such as rheumatoid arthritis, psoriasis and inflammatory bowel disease, but their chronic use can increase susceptibility to infection. Since the lectin-like domain of TNF does not interfere with TNF's anti-bacterial actions, while exerting protective actions in the alveolar-capillary compartments, it is currently evaluated in clinical trials in ARDS and COVID-19. A more comprehensive knowledge of the precise role of the TNFR binding sites versus the lectin-like domain of TNF in lung injury, tissue hypoxia, repair and remodeling may foster the development of novel therapeutics for ARDS.

Management of Acute Lung Injury: Palmitoylethanolamide as a New Approach

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common and devastating clinical disorders with high mortality and no specific therapy. Lipopolysaccharide (LPS) is usually used intratracheally to induce ALI in mice. The aim of this study was to examine the effects of an ultramicronized preparation of palmitoylethanolamide (um-PEA) in mice subjected to LPS-induced ALI. Histopathological analysis reveals that um-PEA reduced alteration in lung after LPS intratracheal administration. Besides, um-PEA decreased wet/dry weight ratio and myeloperoxidase, a marker of neutrophils infiltration, macrophages and total immune cells number and mast cells degranulation in lung. Moreover, um-PEA could also decrease cytokines release of interleukin (IL)-6, interleukin (IL)-1β, tumor necrosis factor (TNF)-α and interleukin (IL)-18. Furthermore, um-PEA significantly inhibited the phosphorylation of nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation in ALI, and at the same time decreased extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38/MAPK) expression, that was increased after LPS administration. Our study suggested that um-PEA contrasted LPS-induced ALI, exerting its potential role as an adjuvant anti-inflammatory therapeutic for treating lung injury, maybe also by p38/NF-κB pathway.

Never Change a Flowing System? The Effects of Retrograde Flow on Isolated Perfused Lungs and Vessels

Retrograde perfusion may occur during disease, surgery or extracorporeal circulation. While it is clear that endothelial cells sense and respond to changes in blood flow, the consequences of retrograde perfusion are only poorly defined. Similar to shear stress or disturbed flow, retrograde perfusion might result in vasomotor responses, edema formation or inflammation in and around vessels. In this study we investigated in rats the effects of retrograde perfusion in isolated systemic vessels (IPV) and in pulmonary vessels of isolated perfused lungs (IPL). Anterograde and retrograde perfusion was performed for 480 min in IPV and for 180 min in the IPL. Perfusion pressure, cytokine levels in perfusate and bronchoalveolar lavage fluid (BALF), edema formation and mRNA expression were studied. In IPV, an increased perfusion pressure and initially also increased cytokine levels were observed during retrograde perfusion. In the IPL, increased edema formation occurred, while cytokine levels were not increased, though dilution of cytokines in BALF due to pulmonary edema cannot be excluded. In conclusion, effects of flow reversal were visible immediately after initiation of retrograde perfusion. Pulmonary edema formation was the only effect of the 3 h retrograde perfusion. Therefore, further research should focus on identification of possible long-term complications of flow reversal.

Chrysophanol Relieves Cisplatin-Induced Nephrotoxicity via Concomitant Inhibition of Oxidative Stress, Apoptosis, and Inflammation

Cisplatin (CDDP) is one of the most frequently prescribed chemotherapy medications. However, its nephrotoxicity which often leads to acute kidney injury (AKI), greatly limits its clinical application. Chrysophanol (CHR), a mainly active anthraquinone ingredient, possesses various biological and pharmacological activities. In this study, we aimed to investigate the underlying protective mechanisms of CHR against CDDP-induced AKI (CDDP-AKI) using C57BL/6 mouse and human proximal tubule epithelial cells. In vivo, we found that pre-treatment with CHR greatly relieved CDDP-AKI and improved the kidney function and morphology. The mechanistic studies indicated that it might alleviate CDDP-AKI by inhibiting oxidative stress, apoptosis, and IKKβ/IκBα/p65/transcription factor nuclear kappa B (NF-κB) inflammation signaling pathway induced by CDDP. Moreover, we found that the cell viability of HK2 cells reduced by CDDP was partially rescued by CHR pre-incubation. Flow cytometry results further indicated that CHR pre-incubation suppressed CDDP induced cellular reactive oxygen species (ROS) generation and inhibited cell apoptosis in a dose-dependent manner. In summary, our results suggested that CHR might be a novel therapy for CDDP-induced AKI.

High mobility group box-1 protects against Aflatoxin G1-induced pulmonary epithelial cell damage in the lung inflammatory environment

Aflatoxin G₁ (AFG₁) is a member of the carcinogenic aflatoxin family. Our previous studies indicated that oral administration of AFG₁ caused tumor necrosis factor (TNF)-α-dependent inflammation that enhanced oxidative DNA damage in alveolar epithelial cells, which may be related to AFG₁-induced lung carcinogenesis. High mobility group box-1 (HMGB1) is a nuclear DNA-binding protein; the intracellular and extracellular roles of HMGB1 have been shown to contribute to DNA repair and sterile inflammation. The role of HMGB1 in DNA damage in an aflatoxin-induced lung inflammatory environment was investigated in this study. Upregulation of HMGB1, TLR2, and RAGE was observed in AFG₁-induced lung inflamed tissues and adenocarcinoma. Blocking AFG₁-induced inflammation by neutralization of TNF-α inhibited the upregulation of HMGB1 in mouse lung tissues, suggesting that AFG₁-induced TNF-α-dependent inflammation regulated HMGB1 expression. In the in vitro human pulmonary epithelial cell line model, Beas-2b, AFG₁ directly enhanced the cytosolic translocation of HMGB1 and its extracellular secretion. The addition of extracellular soluble HMGB1 protected AFG₁-induced DNA damage through the TLR2/NF-κB pathway in Beas-2b cells. In addition, blockade of endogenous HMGB1 by siRNA significantly enhanced AFG₁-induced damage. Thus, our findings showed that both extracellularly-released and nuclear and cytosolic HMGB1 could protect the cell from AFG₁-induced cell damage in a TNF-α-dependent lung inflammatory environment.

The Defensive Action of LYRM03 on LPS-Induced Acute Lung Injury by NF-κB/TLR4/NLRP3 Signals

The aim of the current investigation was to study the role of 3-amino-2-hydroxy-4-phenyl-valyl-isoleucine (LYRM03) in lipopolysaccharide (LPS)-induced acute lung injury (ALI) and investigate its potential pathogenesis. An LPS-induced ALI model was produced with LPS (5 mg/kg) followed by 24 h of injury. Rats were randomly assigned to 6 groups for in vivo experiments: (1) Sham, (2) LYRM03 (20 mg/kg), (3) LPS, (4) LPS plus LYRM03 (5 mg/kg), (5) LPS plus LYRM03 (10 mg/kg), and (6) LPS plus LYRM03 (20 mg/kg). The rat alveolar macrophage cell line (NR8383) cells were divided into 6 groups for in vitro experiments: (1) Sham, (2) LYRM03 (200 μmol/L), (3) LPS (100 ng/mL), (4) LPS plus LYRM03 (50 μmol/L), (5) LPS plus LYRM03 (100 μmol/L), and (6) LPS plus LYRM03 (200 μmol/L). Further study about siRNA targeting NF-κB p65, TLR4, and NLRP3 to explore the potential mechanism of LYRM03 in the LPS-induced ALI models have been done. Therefore, LYRM03 decreased LPS-induced ALI and NR8383 activation as demonstrated through hematoxylin-eosin staining and western blot analysis in vivo and in vitro. LYRM03 ameliorated the content of protein in bronchoalveolar lavage fluid, myeloperoxidase in the lung and malondialdehyde (MDA) in serum. In addition, LYRM03 ameliorated the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-18 (IL-18) in the serum of rats and the supernatant of NR8383 cells. Moreover, LYRM03 significantly inhibited the activities of nuclear factor kappa B (NF-κB), myeloid differentiation factor 88 (MyD88), and toll-like receptor 4 (TLR4). LYRM03 also reduced the increase in the inflammasome, including apoptosis-related speck-like protein containing CARD (ASC), and NOD-like receptor 3 (NLRP3), in LPS-stimulated rats and NR8383 cells. The extent of injury and lung injury scores in the LYRM03 (20 mg/kg) + siRNA targeting NF-κB p65, TLR4, or NLRP3 + LPS-treated rats were higher than that in the LYRM03 (20 mg/kg) + LPS-treated rats. In summary, LYRM03 conferred an intensely lung defensive action on LPS-induced ALI in vivo and in vitro, which could be associated with the abatement of TLR4-induced NLRP3/NF-κB.

Hydrogen sulfide limits neutrophil transmigration, inflammation, and oxidative burst in lipopolysaccharide-induced acute lung injury

Transmigration and activation of neutrophils in the lung reflect key steps in the progression of acute lung injury (ALI). It is known that hydrogen sulfide (H₂S) can limit neutrophil activation, but the respective mechanisms remain elusive. Here, we aimed to examine the underlying pathways in pulmonary inflammation. In vivo, C57BL/6N mice received the H₂S slow releasing compound GYY4137 prior to lipopolysaccharide (LPS) inhalation. LPS challenge led to pulmonary injury, inflammation, and neutrophil transmigration that were inhibited in response to H₂S pretreatment. Moreover, H₂S reduced mRNA expression of macrophage inflammatory protein-2 (MIP-2) and its receptor in lung tissue, as well as the accumulation of MIP-2 and interleukin-1β in the alveolar space. In vitro, GYY4137 did not exert toxic effects on Hoxb8 neutrophils, but prevented their transmigration through an endothelial barrier in the presence and absence of MIP-2. In addition, the release of MIP-2 and reactive oxygen species from LPS-stimulated Hoxb8 neutrophils were directly inhibited by H₂S. Taken together, we provide first evidence that H₂S limits lung neutrophil sequestration upon LPS challenge. As proposed underlying mechanisms, H₂S prevents neutrophil transmigration through the inflamed endothelium and directly inhibits pro-inflammatory as well as oxidative signalling in neutrophils. Subsequently, H₂S pretreatment ameliorates LPS-induced ALI.

The Protective Effects of a Synthetic Geranyl Acetophenone in a Cellular Model of TNF-α-Induced Pulmonary Epithelial Barrier Dysfunction

Alveolar epithelial barrier dysfunction contributes to lung edema and can lead to acute lung injury (ALI). The features include increased epithelial permeability, upregulation of inflammatory mediators and downregulation of junctional complex molecules; these changes are often induced by inflammation. tHGA is an acetophenone analogue with therapeutic potential in asthma. Its therapeutic potential in ALI is presently unknown. Herein, the effects of tHGA on epithelial barrier dysfunction were determined in TNF-α-induced human alveolar epithelial cells. The anti-inflammatory properties of tHGA were assessed by monocyte adhesion assay and analysis of MCP-1 and ICAM-1 expression. The epithelial barrier function was assessed by paracellular permeability and transepithelial electrical resistance (TEER) assays, and analysis of junctional complex molecules expression. To elucidate the mechanism of action, the effects of tHGA on the NF-κB and MAPK pathways were determined. Gene and protein expression were analyzed by RT-PCR and Western blotting or ELISA, respectively. tHGA suppressed leukocyte adhesion to TNF-α-induced epithelium and reduced MCP-1 and ICAM-1 gene expression and secretion. tHGA also increased TEER readings, reduced epithelial permeability and enhanced expression of junctional complex molecules (zona occludens-1, occludin and E-cadherin) in TNF-α-induced cells. Correspondingly, the NF-κB, ERK and p38 MAPK pathways were also inhibited by tHGA. These findings suggest that tHGA is able to preserve alveolar epithelial barrier function in response to acute inflammation, via its anti-inflammatory activity and stabilization of epithelial barrier integrity, mediated by NF-κB, ERK and p38 MAPK signaling.

MiR-21/STAT3 Signal Is Involved in Odontoblast Differentiation of Human Dental Pulp Stem Cells Mediated by TNF-α

Dental pulp stem cells (DPSCs), as one type of mesenchymal stem cells (MSCs), have the capability of self-renewal and multipotency to differentiate into several cell lineages, including osteogenesis, odontoblasts, chondrogenesis, neurogenesis, and adipogenesis. It has found that tumor necrosis factor-α (TNF-α) can promote osteogenic differentiation of human DPSCs in our previous studies. Other experimentation revealed that signal transducer and activator of transcription 3 (STAT3) underwent a rapid activation both in osteogenesis and inflammation microenvironment of MSCs in vitro. MicroRNAs (miRNAs or miRs) have been proved in previous studies to regulate MSCs differentiation in vitro. In this study, we identified miR-21 as a key miRNA contributed the functional axis of odontoblast differentiation induced by STAT3. It is observed that the expression of miR-21 and STAT3 increased gradually in low concentration (1-10 ng/mL) of TNF-α, while they were suppressed in high concentration (50-100 ng/mL). The upregulation of miR-21 may facilitate the odontoblast differentiation of DPSCs coordinating with STAT3. SiSTAT3 or treated by the inhibitor of STAT3, cucurbitacin I (Cuc I), significantly increased primary miR-21 expression along with decreased mature miR-21 expression. Meanwhile, the inhibition of miR-21 (anti-miR-21) decreased the activation of STAT3 as well as suppressed the marker proteins of odontoblast differentiation. The results revealed a new function of miR-21, suggesting that miR-21/STAT3 signal may act as a modulator within a complex network of factors to regulate odontoblast differentiation of human DPSCs. It may provide a novel therapeutic strategy to regulate the odontoblast differentiation of DPSCs.

Preventive and Therapeutic Effects of Thymol in a Lipopolysaccharide-Induced Acute Lung Injury Mice Model

Acute lung injury (ALI) is a life-threatening syndrome which causes a high mortality rate worldwide. In traditional medicine, lots of aromatic plants-such as some Thymus species-are used for treatment of various lung diseases including pertussis, bronchitis, and asthma. Thymol, one of the primary active constituent derived from Thymus vulgaris (thyme), has been reported to exhibit potent anti-microbial, anti-oxidant, and anti-inflammatory activities in vivo and in vitro. The present study aims to investigate the protective effects of thymol in lipopolysaccharide (LPS)-induced lung injury mice model. In LPS-challenged mice, treatment with thymol (100 mg/kg) before or after LPS challenge significantly improved pathological changes in lung tissues. Thymol also inhibited the LPS-induced inflammatory cells influx, TNF-α and IL-6 releases, and protein concentration in bronchoalveolar lavage fluid (BALF). Additionally, thymol markedly inhibited LPS-induced elevation of MDA and MPO levels, as well as reduction of SOD activity. Further study demonstrated that thymol effectively inhibited the NF-κB activation in the lung. Taken together, these results suggested that thymol might be useful in the therapy of acute lung injury.

Polydeoxyribonucleotide Ameliorates Lipopolysaccharide-Induced Lung Injury by Inhibiting Apoptotic Cell Death in Rats

Lung injury is characterized by diffuse lung inflammation, alveolar-capillary destruction, and alveolar flooding, resulting in respiratory failure. Polydexyribonucleotide (PDRN) has an anti-inflammatory effect, decreasing inflammatory cytokines, and suppressing apoptosis. Thus, we investigated its efficacy in the treatment of lung injury, which was induced in rats using lipopolysaccharide (LPS). Rats were randomly divided into three groups according to sacrifice time, and each group split into control, lung injury-induced, and lung injury-induced + PDRN-treated groups. Rats were sacrificed 24 h and 72 h after PDRN administration, according to each group. Lung injury was induced by intratracheal instillation of LPS (5 mg/kg) in 0.2 mL saline. Rats in PDRN-treated groups received a single intraperitoneal injection of 0.3 mL distilled water including PDRN (8 mg/kg), 1 h after lung injury induction. Percentages of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive, cleaved caspase-3-, -8-, and -9-positive cells, the ratio of Bcl-2-associated X protein (Bax) to B-cell lymphoma 2 (Bcl-2), and expressions of inflammatory cytokines (tumor necrosis factor-α, interleukin-6) were decreased by PDRN treatment in the LPS-induced lung injury rats. Therefore, treatment with PDRN reduced lung injury score. This anti-apoptotic effect of PDRN can be ascribed to the enhancing effect of PDRN on adenosine A_2A receptor expression. Based on these results, PDRN might be considered as a new therapeutic agent for the treatment of lung injury.

Perioperative "remote" acute lung injury: recent update

Perioperative acute lung injury (ALI) is a syndrome characterised by hypoxia and chest radiograph changes. It is a serious post-operative complication, associated with considerable mortality and morbidity. In addition to mechanical ventilation, remote organ insult could also trigger systemic responses which induce ALI. Currently, there are limited treatment options available beyond conservative respiratory support. However, increasing understanding of the pathophysiology of ALI and the biochemical pathways involved will aid the development of novel treatments and help to improve patient outcome as well as to reduce cost to the health service. In this review we will discuss the epidemiology of peri-operative ALI; the cellular and molecular mechanisms involved on the pathological process; the clinical considerations in preventing and managing perioperative ALI and the potential future treatment options.

Tight junctions in pulmonary epithelia during lung inflammation

Inflammatory lung diseases like asthma bronchiale, chronic obstructive pulmonary disease and allergic airway inflammation are widespread public diseases that constitute an enormous burden to the health systems. Mainly classified as inflammatory diseases, the treatment focuses on strategies interfering with local inflammatory responses by the immune system. Inflammatory lung diseases predispose patients to severe lung failures like alveolar oedema, respiratory distress syndrome and acute lung injury. These life-threatening syndromes are caused by increased permeability of the alveolar and airway epithelium and exudate formation. However, the mechanism underlying epithelium barrier breakdown in the lung during inflammation is elusive. This review emphasises the role of the tight junction of the airway epithelium as the predominating structure conferring epithelial tightness and preventing exudate formation and the impact of inflammatory perturbations on their function.

Treatment with Isorhamnetin Protects the Brain Against Ischemic Injury in Mice

Ischemic stroke is a major cause of morbidity and mortality, yet lacks effective neuroprotective treatments. The aim of this work was to investigate whether treatment with isorhamnetin protected the brain against ischemic injury in mice. Experimental stroke mice underwent the filament model of middle cerebral artery occlusion with reperfusion. Treatment with isorhamnetin or vehicle was initiated immediately at the onset of reperfusion. It was found that treatment of experimental stroke mice with isorhamnetin reduced infarct volume and caspase-3 activity (a biomarker of apoptosis), and improved neurological function recovery. Treatment of experimental stroke mice with isorhamnetin attenuated cerebral edema, improved blood-brain barrier function, and upregulated gene expression of tight junction proteins including occludin, ZO-1, and claudin-5. Treatment of experimental stroke mice with isorhamnetin activated Nrf2/HO-1, suppressed iNOS/NO, and led to reduced formation of MDA and 3-NT in ipsilateral cortex. In addition, treatment of experimental stroke mice with isorhamnetin suppressed activity of MPO (a biomarker of neutrophil infiltration) and reduced protein levels of IL-1β, IL-6, and TNF-α in ipsilateral cortex. Furthermore, it was found that treatment of experimental stroke mice with isorhamnetin reduced mRNA and protein expression of NMDA receptor subunit NR1 in ipsilateral cortex. In conclusion, treatment with isorhamnetin protected the brain against ischemic injury in mice. Isorhamnetin could thus be envisaged as a countermeasure for ischemic stroke but remains to be tested in humans.