Leukotriene B₄-leukotriene B₄ receptor axis promotes oxazolone-induced contact dermatitis by directing skin homing of neutrophils and CD8⁺ T cells

Topical Application of a PDE4 Inhibitor Ameliorates Atopic Dermatitis through Inhibition of Basophil IL-4 Production

Phosphodiesterase 4 inhibitors have been approved for the treatment of atopic dermatitis. However, the cellular and molecular mechanisms underlying their therapeutic effect remain to be fully elucidated. In this study, we addressed this unsolved issue by analyzing the action of difamilast, a novel phosphodiesterase 4 inhibitor, on an oxazolone-induced skin allergic inflammation commonly used as a mouse model of atopic dermatitis. Topical application of difamilast ameliorated skin inflammation in association with reduced IL-4 expression even when the treatment commenced 4 days after the initiation of oxazolone challenge, showing its therapeutic effect on atopic dermatitis. IL-4-deficient mice displayed milder skin inflammation than did wild-type mice, and the difamilast treatment had little or no further therapeutic effect. This was also the case in mice depleted of basophils, predominant producers of IL-4 in the skin lesion, suggesting that difamilast may act on basophils. Notably, basophils accumulating in the skin lesion showed highly upregulated expression of Pde4b encoding the B subtype of the phosphodiesterase 4 family. Difamilast suppressed IL-4 production from basophils activated in vitro, at least in part, through inhibition of ERK phosphorylation. Taken together, difamilast appeared to ameliorate atopic dermatitis inflammation through the suppression of basophil IL-4 production in the skin lesion.

Regulation of T-Cell Immune Responses by Pro-Resolving Lipid Mediators

Both the initiation and the resolution of inflammatory responses are governed by the sequential activation, migration, and control/suppression of immune cells at the site of injury. Bioactive lipids play a major role in the fine-tuning of this dynamic process in a timely manner. During inflammation and its resolution, polymorphonuclear cells (PMNs) and macrophages switch from producing pro-inflammatory prostaglandins and leukotrienes to specialized pro-resolving lipid mediators (SPMs), namely, lipoxins, resolvins, protectins, and maresins, which are operative at the local level to limit further inflammation and tissue injury and restore homeostasis. Accumulating evidences expand now the role and actions of these lipid mediators from innate to adaptive immunity. In particular, SPMs have been shown to contribute to the control of chronic inflammation, and alterations in their production and/or function have been associated with the persistence of several pathological conditions, including autoimmunity, in human and experimental models. In this review, we focus on the impact of pro-resolving lipids on T cells through their ability to modulate T-cell responses. In particular, the effects of the different families of SPMs to restrain effector T-cell functions while promoting regulatory T cells will be reviewed, along with the underlying mechanisms. Furthermore, the emerging concept of SPMs as new biological markers for disease diagnostic and progression and as putative therapeutic tools to regulate the development and magnitude of inflammatory and autoimmune diseases is discussed.

The Kinetics of Lymphatic Dysfunction and Leukocyte Expansion in the Draining Lymph Node during LTB4 Antagonism in a Mouse Model of Lymphedema

The mechanisms of lymphedema development are not well understood, but emerging evidence highlights the crucial role the immune system plays in driving its progression. It is well known that lymphatic function deteriorates as lymphedema progresses; however, the connection between this progressive loss of function and the immune-driven changes that characterize the disease has not been well established. In this study, we assess changes in leukocyte populations in lymph nodes within the lymphatic drainage basin of the tissue injury site (draining lymph nodes, dLNs) using a mouse tail model of lymphedema in which a pair of draining collecting vessels are left intact. We additionally quantify lymphatic pump function using established near infrared (NIR) lymphatic imaging methods and lymph-draining nanoparticles (NPs) synthesized and employed by our team for lymphatic tissue drug delivery applications to measure lymphatic transport to and resulting NP accumulation within dLNs associated with swelling following surgery. When applied to assess the effects of the anti-inflammatory drug bestatin, which has been previously shown to be a possible treatment for lymphedema, we find lymph-draining NP accumulation within dLNs and lymphatic function to increase as lymphedema progresses, but no significant effect on leukocyte populations in dLNs or tail swelling. These results suggest that ameliorating this loss of lymphatic function is not sufficient to reverse swelling in this surgically induced disease model that better recapitulates the extent of lymphatic injury seen in human lymphedema. It also suggests that loss of lymphatic function during lymphedema may be driven by immune-mediated mechanisms coordinated in dLNs. Our work indicates that addressing both lymphatic vessel dysfunction and immune cell expansion within dLNs may be required to prevent or reverse lymphedema when partial lymphatic function is sustained.

Suppression of Th17 cell differentiation via sphingosine-1-phosphate receptor 2 by cinnamaldehyde can ameliorate ulcerative colitis

Ulcerative colitis (UC) is chronic disease characterized by diffuse inflammation of the mucosa of the colon and rectum. Although the etiology is unknown, dysregulation of the intestinal mucosal immune system is closely related to UC. Cinnamaldehyde (CA) is a major active compound from cinnamon, is known as its anti-inflammatory and antibacterial. However, little research focused on its regulatory function on immune cells in UC. Therefore, we set out to explore the modulating effects of CA on immune cells in UC. We found that CA reduced the progression of colitis through controlling the production of proinflammatory cytokines and inhibiting the proportion of Th17 cells. Furthermore, the liquid chromatography-mass spectrometry (LC-MS) method was employed for analyzing and differentiating metabolites, data showed that sphingolipid pathway has a great influence on the effect of CA on UC. Meanwhile, sphingosine-1-phosphate receptor 2 (S1P2) and Rho-GTP protein levels were downregulated in colonic tissues after CA treatment. Moreover, in vitro assays showed that CA inhibited Th17 cell differentiation and downregulated of S1P2 and Rho-GTP signaling. Notably, we found that treatment with S1P2 antagonist (JTE-013) weakened the inhibitory effect of CA on Th17 cells. Furthermore, S1P2 deficiency (S1P2-/-) blocked the effect of CA on Th17 cell differentiation. In addition, CA can also improve inflammation via lncRNA H19 and MIAT. To sum up, this study provides clear evidence that CA can ameliorate ulcerative colitis through suppressing Th17 cells via S1P2 pathway and regulating lncRNA H19 and MIAT, which further supports S1P2 as a potential drug target for immunity-mediated UC.

The role of the LTB4-BLT1 axis in health and disease

Leukotriene B4 (LTB4) is a major type of lipid mediator that is rapidly generated from arachidonic acid through sequential action of 5-lipoxygenase (5-LO), 5-lipoxygenase-activating protein (FLAP) and LTA4 hydrolase (LTA4H) in response to various stimuli. LTB4 is well known to be a chemoattractant for leukocytes, particularly neutrophils, via interaction with its high-affinity receptor BLT1. Extensive attention has been paid to the role of the LTB4-BLT1 axis in acute and chronic inflammatory diseases, such as infectious diseases, allergy, autoimmune diseases, and metabolic disease via mediating recruitment and/or activation of different types of inflammatory cells depending on different stages or the nature of inflammatory response. Recent studies also demonstrated that LTB4 acts on non-immune cells via BLT1 to initiate and/or amplify pathological inflammation in various tissues. In addition, emerging evidence reveals a complex role of the LTB4-BLT1 axis in cancer, either tumor-inhibitory or tumor-promoting, depending on the different target cells. In this review, we summarize both established understanding and the most recent progress in our knowledge about the LTB4-BLT1 axis in host defense, inflammatory diseases and cancer.

Promotion of Myofibroblast Differentiation and Tissue Fibrosis by the Leukotriene B4 -Leukotriene B4 Receptor Axis in Systemic Sclerosis

OBJECTIVE

To investigate the role of the inflammatory lipid mediator leukotriene B₄ (LTB₄ ) and its receptor, BLT1, in the development and progression of systemic sclerosis (SSc).

METHODS

Serum levels of LTB₄ were compared in 64 patients with SSc and 80 healthy controls. Skin and lung tissue sections from patients with SSc and healthy donors were immunostained for leukotriene A₄ hydrolase (LTA₄ H), the critical enzyme for LTB₄ synthesis, and BLT1, in combination with different cell markers. In mouse models of SSc using bleomycin or angiotensin II challenge or immunization with the DNA topoisomerase I, genetic or pharmacologic interruption of the LTB₄ -BLT1 axis in mice was carried out to assess its effects on systemic disease features and myofibroblast markers. Immunoblotting was performed to examine the signaling pathway in fibroblasts and endothelial cells following stimulation with LTB₄ or with serum from SSc patients.

RESULTS

Serum LTB₄ levels were 44.93% higher in patients with SSc than in matched healthy controls (mean ± SD 220.3 ± 74.75 pg/ml versus 152.0 ± 68.05 pg/ml; P < 0.0001), and this was associated with the patient subsets of SSc-associated interstitial lung disease and diffuse cutaneous SSc. Levels of LTA₄ H and BLT1 were increased in lesional areas of the skin and lungs of SSc patients, and both were abundant in myofibroblasts and endothelial cells. Interruption of the LTB₄ -BLT1 axis in mouse models of SSc significantly mitigated dermal and pulmonary fibrosis, with 54.00% and 52.65% fewer α-smooth muscle actin-positive myofibroblasts accumulating in the skin and lungs of mice, respectively, after bleomycin challenge. Immunoblotting of cultures with recombinant LTB₄ -stimulated fibroblasts and endothelial cells or with serum from SSc patients showed that fibroblast-myofibroblast and endothelial-mesenchymal transitions were promoted via BLT1, and that this was dependent on activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/mechanistic target of rapamycin (mTOR) pathway but independent of the release of transforming growth factor β (TGFβ) by fibroblasts or endothelial cells.

CONCLUSION

The LTB₄ -BLT1 axis may contribute to fibrosis in SSc by directly promoting myofibroblast differentiation via the PI3K/Akt/mTOR pathway, and this appears to operate independently of autocrine secretion of TGFβ.

Spleen Oxylipin and Polyunsaturated Fatty Acid Profiles are Altered by Dietary Source of Polyunsaturated Fatty Acid and by Sex

As the largest secondary lymphoid organ, the spleen plays an important role in immune responses. The role of arachidonic acid (ARA) and its 20-carbon eicosanoids in modulating immune function has long been of interest. However, recent advances have enabled the identification of numerous other n-6 and n-3 polyunsaturated fatty acid (PUFA)-derived oxylipins. Here, we investigate the effects of diet and sex on the spleen nonesterified oxylipin profiles and phospholipid and neutral lipid PUFA composition in Sprague-Dawley rats supplemented with oils rich in α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), or linoleic acid. Dietary ALA, EPA, and DHA resulted in lower levels of ARA and ARA oxylipins. Oxylipins derived from other n-6 PUFA were also reduced despite no or opposite effect on their PUFA levels. Each diet also resulted in higher levels of oxylipins almost exclusively derived from the supplemented PUFA, despite PUFA in the same biosynthetic pathway also often being increased. Further, while oxylipin differences often reflected changes to phospholipid PUFA, there were instances where they corresponded more closely to changes in neutral lipid PUFA. With respect to sex effects, >50% of lipoxygenase ARA-derived oxylipins were higher in males in at least one diet group, while multiple DHA oxylipins were lower in males only in rats provided the DHA diet. This fundamental description of oxylipin composition in the spleen, including the influence of diet and sex and the relationship to PUFA composition, will help inform future studies examining the functions of these oxylipins under physiological and pathological conditions.

Neutrophil chemoattractant receptors in health and disease: double-edged swords

Neutrophils are frontline cells of the innate immune system. These effector leukocytes are equipped with intriguing antimicrobial machinery and consequently display high cytotoxic potential. Accurate neutrophil recruitment is essential to combat microbes and to restore homeostasis, for inflammation modulation and resolution, wound healing and tissue repair. After fulfilling the appropriate effector functions, however, dampening neutrophil activation and infiltration is crucial to prevent damage to the host. In humans, chemoattractant molecules can be categorized into four biochemical families, i.e., chemotactic lipids, formyl peptides, complement anaphylatoxins and chemokines. They are critically involved in the tight regulation of neutrophil bone marrow storage and egress and in spatial and temporal neutrophil trafficking between organs. Chemoattractants function by activating dedicated heptahelical G protein-coupled receptors (GPCRs). In addition, emerging evidence suggests an important role for atypical chemoattractant receptors (ACKRs) that do not couple to G proteins in fine-tuning neutrophil migratory and functional responses. The expression levels of chemoattractant receptors are dependent on the level of neutrophil maturation and state of activation, with a pivotal modulatory role for the (inflammatory) environment. Here, we provide an overview of chemoattractant receptors expressed by neutrophils in health and disease. Depending on the (patho)physiological context, specific chemoattractant receptors may be up- or downregulated on distinct neutrophil subsets with beneficial or detrimental consequences, thus opening new windows for the identification of disease biomarkers and potential drug targets.

The Role of Leukotrienes as Potential Therapeutic Targets in Allergic Disorders

Leukotrienes (LTs) are lipid mediators that play pivotal roles in acute and chronic inflammation and allergic diseases. They exert their biological effects by binding to specific G-protein-coupled receptors. Each LT receptor subtype exhibits unique functions and expression patterns. LTs play roles in various allergic diseases, including asthma (neutrophilic asthma and aspirin-sensitive asthma), allergic rhinitis, atopic dermatitis, allergic conjunctivitis, and anaphylaxis. This review summarizes the biology of LTs and their receptors, recent developments in the area of anti-LT strategies (in settings such as ongoing clinical studies), and prospects for future therapeutic applications.

Eicosanoid and Specialized Proresolving Mediator Regulation of Lymphoid Cells

Eicosanoids and specialized proresolving mediators (SPMs) regulate leukocyte function and inflammation. They are ideally positioned at the interface of the innate and adaptive immune responses when lymphocytes interact with leukocytes. Receptors for leukotriene B₄ (LTB₄), prostaglandin E₂ (PGE₂), and SPMs are expressed on lymphocytes. Evidence points toward an essential role of these lipid mediators (LMs) in direct regulation of lymphocyte functions. SPMs, which include lipoxins, demonstrate comprehensive protective actions with lymphocytes. LTB₄ and PGE₂ regulation of lymphocytes is diverse and depends on the interaction of lymphocytes with other cells. Importantly, both LTB₄ and PGE₂ are essential regulators of T cell antitumor activity. These LMs are attractive therapeutic targets to control dysregulated innate and adaptive immune responses, promote lymphocyte antitumor activity, and prevent tumor immune evasion.

Importance of the leukotriene B4-BLT1 and LTB4-BLT2 pathways in asthma

For several decades, the leukotriene pathways have been implicated as playing a central role in the pathophysiology of asthma. The presence and elevation of numerous metabolites in the blood, sputum, and bronchoalveolar lavage fluid from asthmatics or experimental animals adds support to this notion. However, targeting of the leukotriene pathways has had, in general, limited success. The single exception in asthma therapy has been targeting of the cysteinyl leukotriene receptor 1, which clinically has proven effective but only in certain clinical situations. Interference with 5-lipoxygenase has had limited success, in part due to adverse drug effects. The importance of the LTB4-BLT1 pathway in asthma pathogenesis has extensive experimental support and findings, albeit limited, from clinical samples. The LTB4-BLT1 pathway was shown to be important as a neutrophil chemoattractant. Despite observations made more than two decades ago, the LTB4-BLT1 pathway has only recently been shown to exhibit important activities on subsets of T lymphocytes, both as a chemoattractant and on lymphocyte activation, as well as on dendritic cells, the major antigen presenting cell in the lung. The role of BLT2 in asthma remains unclear. Targeting of components of the LTB4-BLT1 pathway offers innovative therapeutic opportunities especially in patients with asthma that remain uncontrolled despite intensive corticosteroid treatment.

The role of the LTB4-BLT1 axis in chemotactic gradient sensing and directed leukocyte migration

Directed leukocyte migration is a hallmark of inflammatory immune responses. Leukotrienes are derived from arachidonic acid and represent a class of potent lipid mediators of leukocyte migration. In this review, we summarize the essential steps leading to the production of LTB₄ in leukocytes. We discuss the recent findings on the exosomal packaging and transport of LTB₄ in the context of chemotactic gradients formation and regulation of leukocyte recruitment. We also discuss the dynamic roles of the LTB₄ receptors, BLT1 and BLT2, in mediating chemotactic signaling in leukocytes and contrast them to other structurally related leukotrienes that bind to distinct GPCRs. Finally, we highlight the specific roles of the LTB₄-BLT1 axis in mediating signal-relay between chemotaxing neutrophils and its potential contribution to a wide variety of inflammatory conditions including tumor progression and metastasis, where LTB₄ is emerging as a key signaling component.

Inhibition of COX-2/mPGES-1 and 5-LOX in macrophages by leonurine ameliorates monosodium urate crystal-induced inflammation

Cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX) and microsomal prostaglandin E synthase-1 (mPGES-1)-derived eicosanoids play an essential role in human inflammatory disorders. Here, we investigated whether inhibition of COX-2/mPGES-1 and 5-LOX in macrophages by leonurine ameliorates monosodium urate (MSU) crystal-induced inflammation. Virtual screening assay and in vitro enzyme inhibition assay showed that leonurine was a potential inhibitor of COX-2, mPGES-1 and 5-LOX. Compared with COX-2 inhibitor celecoxib, leonurine (30 mg/kg) significantly decreased ankle perimeter, gait score and neutrophil number in synovial fluid in MSU crystal-treated rats, accompanied with the decreased expression of COX-2, mPGES-1 and 5-LOX and production of prostaglandin E₂ (PGE₂) and leukotriene B₄ (LTB₄) in the synovial fluid macrophages. In addition, leonurine decreased representative M1 marker (iNOS and CD86) expression, NLRP3 inflammasome activation and M1 cytokine (TNF-α and IL-1β) production. In the in vitro cultured RAW264.7 and human monocyte-derived macrophages (MDMs), blockade of COX-2/mPGES-1 and 5-LOX by leonurine inhibited macrophage M1 polarization and NLRP3 inflammasome activation in response to MSU crystals, and thus down-regulated IL-1β and TNF-α with STAT1 and NF-κB inactivation. Conversely, these effects were partially abolished by overexpression of COX-2, mPGES-1, 5-LOX or STAT1. Furthermore, leonurine prevented a positive feedback loop between COX-2/mPGES-1/5-LOX and IL-1β/TNF-α in MSU crystal-induced inflammation. Together, simultaneous down-regulation of COX-2/mPGES-1 and 5-LOX by leonurine ameliorates MSU crystal-induced inflammation through decreasing IL-1β and TNF-α production. Our study may provide novel multi-target agents toward the arachidonic acid (AA) network for gouty arthritis therapy.

Neutrophil-lymphatic interactions during acute and chronic disease

The lymphatic system aids in osmoregulation through tissue fluid transport, but is also designed to support communication between cells of the innate and adaptive immune systems. During inflammation, changes within the lymphatics can result in an altered response to infection. Neutrophils have been described as one key cell type that facilitates antigen capture and presentation within the lymphatic system, enabling an effective adaptive immune response. Disruption of neutrophil recruitment during inflammation, due to alterations in lymphatics, is a growing area of study due to their key role in infection resolution. In this review, we discuss the currently known methods by which neutrophils are recruited to the lymphatic system and what subsequent effects they have on resident and recruited cells within the lymph vessels and nodes. We also discuss the changes in neutrophil activation and recruitment during chronic inflammatory diseases and their relationship to lymphatic dysfunction.

Pathomechanisms of Contact Sensitization

Contact sensitization is the initial process involved in the development of an allergic reaction to xenobiotic environmental substances. Here, we briefly describe the differences between irritant and allergic contact dermatitis. Then, we highlight the essential steps involved in the development of an ACD reaction, i.e., the protein binding of haptens, genetic factors influencing the penetration of sensitizers into the skin, the different mechanisms driving the initial development of an inflammatory cytokine micromilieu enabling the full maturation of dendritic cells, the role of pre- and pro-haptens, antigen presentation and T cell activation via MHC and CD1 molecules, dendritic cell (DC) migration, and potential LC contribution as well as the different T cell subsets involved in ACD. In addition, we discuss the latest publications regarding factors that might influence the sensitizing potential such as repeated sensitizer application, penetration enhancers, humidity of the skin, microbiota, Tregs, and phthalates. Last but not least, we briefly touch upon novel targets for drug development that might serve as treatment options for ACD.

The leukotriene B4-leukotriene B4 receptor axis promotes cisplatin-induced acute kidney injury by modulating neutrophil recruitment

Cisplatin is an effective chemotherapeutic agent and widely used in treatment of various solid organ malignancies, including head and neck, ovarian, and testicular cancers. However, the induction of acute kidney injury (AKI) is one of its main side effects. Leukotriene B₄ receptor 1 (BLT1) mediates the majority of physiological effects of leukotriene B₄ (LTB₄), a potent lipid chemoattractant generated at inflammation sites, but the role of the LTB₄-BLT1 axis in cisplatin-induced AKI remains unknown. Here we found upregulated LTB₄ synthesis and BLT1 expression in the kidney after cisplatin administration. Cisplatin was found to directly upregulate gene expression of leukotriene A₄ hydrolase and stimulate LTB₄ production in renal tubular epithelial cells. Reduced kidney structural/functional damage, inflammation, and apoptosis were observed in BLT1^-/- mice, as well as in wild-type mice treated with the LTA4H inhibitor SC-57461A and the BLT1 antagonist U-75302. Neutrophils were likely the target of this pathway, as BLT1 absence induced a significant decrease in infiltrating neutrophils in the kidney. Adoptive transfer of neutrophils from wild-type mice restored kidney injury in BLT1^-/- mice following cisplatin challenge. Thus, the LTB₄-BLT1 axis contributes to cisplatin-induced AKI by mediating kidney recruitment of neutrophils, which induce inflammation and apoptosis in the kidney. Hence, the LTB₄-BLT1 axis could be a potential therapeutic target in cisplatin-induced AKI.

Inhibition of leukotriene B4 receptor 1 attenuates lipopolysaccharide-induced cardiac dysfunction: role of AMPK-regulated mitochondrial function

Leukotriene B4 (LTB4)-mediated leukocyte recruitment and inflammatory cytokine production make crucial contributions to chronic inflammation and sepsis; however, the role of LTB4 in lipopolysaccharide (LPS)-induced cardiac dysfunction remains unclear. Therefore, the present study addressed this issue using an LTB4 receptor 1 (BLT1) inhibitor. Administration of LPS to mice resulted in decreased cardiovascular function. Inhibition of LTB4/BLT1 with the BLT1 inhibitor U75302 significantly improved survival and attenuated the LPS-induced acute cardiac dysfunction. During LPS challenge, the phosphorylated AMPK/ACC signaling pathway was slightly activated, and this effect was enhanced by U75302. Additionally, pNF-κB, Bax and cleaved caspase-3 were upregulated by LPS, and Bcl-2, IκB-α, mitochondrial complex I, complex II, and OPA1 were downregulated; however, these effects were reversed by U75302. The results indicated that the BLT1 antagonist suppressed cardiac apoptosis, inflammation, and mitochondrial impairment. Furthermore, the protection provided by the BLT1 inhibitor against LPS-induced cardiac dysfunction was significantly reversed by the AMPK inhibitor Compound C. In conclusion, inhibiting the LTB4/BLT1 signaling pathway via AMPK activation is a potential treatment strategy for septic cardiac dysfunction because it efficiently attenuates cardiac apoptosis, which may occur via the inhibition of inflammation and mitochondrial dysfunction.

BLT1 Mediates Bleomycin-Induced Lung Fibrosis Independently of Neutrophils and CD4+ T Cells

Leukotriene B₄ (LTB4) and its functional receptor BLT1 are closely involved in tissue inflammation by primarily mediating leukocyte recruitment and activation. Elevated LTB4 was reported in patients with lung fibrosis; however, the role of the LTB4/BLT1 axis in lung fibrosis remains unknown. In this study, we demonstrated that BLT1^-/- mice exhibited significantly attenuated bleomycin (BLM)-induced lung fibrosis. Interestingly, BLT1 blockade with its specific antagonist U75302 in the acute injury phase (days 0-10 after BLM treatment) significantly attenuated lung fibrosis, which was accompanied by significant decreases in early infiltrating neutrophils and later infiltrating CD4⁺ T cells and the production of TGF-β, IL-13, and IL-17A. In contrast, BLT1 blockade in the fibrotic phase (days 10-21 after BLM treatment) had no effect on lung fibrosis and TGF-β production, although it significantly decreased CD4⁺ T cell infiltration. Furthermore, depletion of neutrophils or CD4⁺ T cells had no effect on BLM-induced lung fibrosis, suggesting the independence of profibrotic activity of the LTB4/BLT1 axis on BLT1-dependent lung recruitment of these two leukocytes. Finally, although BLT1 blockade had no effect on the recruitment and phenotype of macrophages in BLM-induced lung fibrosis, the LTB4/BLT1 axis could promote TGF-β production by macrophages stimulated with BLM or supernatants from BLM-exposed airway epithelial cells in an autocrine manner, which further induced collagen secretion by lung fibroblasts. Collectively, our study demonstrates that the LTB4/BLT1 axis plays a critical role in acute injury phase to promote BLM-induced lung fibrosis, and it suggests that early interruption of the LTB4/BLT1 axis in some inflammatory diseases could prevent the later development of tissue fibrosis.

Coenzyme Q10 Suppresses TNF-α-Induced Inflammatory Reaction In Vitro and Attenuates Severity of Dermatitis in Mice

Anti-oxidant coenzyme Q10 (Co-Q10) is commonly used in clinic. Recently, Co-Q10 was reported to antagonize TNF-α-induced inflammation and play a protective role in various inflammatory conditions. However, its role in dermatitis is unknown. Herein, RAW264.7 macrophage cell line was cultured with stimulation of TNF-α, and administration of Co-Q10 alleviated TNF-α-mediated inflammatory reaction in vitro. Furthermore, oxazolone-induced dermatitis mice model was established, and treatment of Co-Q10 markedly attenuated dermatitis phenotype in this mice model. Moreover, the protective role of Co-Q10 in vitro and in dermatitis was probably due to its repression on NF-κB signaling. Collectively, Co-Q10 may represent a potential molecular target for prevention and treatment of inflammatory skin diseases.

Naringenin inhibits spinal cord injury-induced activation of neutrophils through miR-223

Naringenin (NR), a flavonoid abundant in citrus fruits has been reported to possess anti-inflammatory properties. The present study aimed to investigate the protective of naringenin in rats after spinal cord injury (SCI) and the underlying mechanisms associated with neuroinflammation. Adult male Sprague-Dawley rats were subjected to laminectomy at T9-T11 and compression with a vascular clip. The spinal cords spanning the injury site about 0.8cm were collected for testing. There were five groups (n=7 in each group): (a) Control group; (b) sham group group; (c) SCI+saline; (d) SCI+NR (50mg/kg, p.o.) group and (e) SCI+NR (100mg/kg, p.o.) group. Different doses of NR (50mg/kg, p.o. and 100mg/kg, p.o.) or saline were administered once daily for 11 consecutive days, from 3days prior to surgery to 7days after surgery. The expression level of miR-223, NLRP3 and IL-1β were measured by RT- qPCR. The accumulation of neutrophils at the site of compression, as evaluated by measuring the tissue myeloperoxidase activity, significantly increased with time following the compression, peaking at 24h post compression. The expression of miR-223 was significant elevated in (b). However, spinal cord myeloperoxidase activity and the expression of miR-223 did not increase in sham-operated animals. NR significantly inhibited a SCI-induced activation of neutrophils through repressed miR-223 in group (d) and (e). There was a better effect in group (e) than group (d). miR-223 is thought to act as a fine-tuner of granulocyte production and the inflammatory response. Our findings suggested that repeated administration of naringenin (100mg/kg, p.o) may provide the protective effect of the spinal cord injury in rats, possibly through inhibiting neuroinflammation.