Lipoxin A4 promotes adipogenic differentiation and browning of mouse embryonic fibroblasts.

Recently, it has been irrefutably discovered that brown adipocytes dissipate energy as heat and protect against obesity. Researchers make great efforts to explore approaches for its activation. Lipoxin A4 (LXA4) has been proven to reverse adipose tissue inflammation and improve insulin resistance, but its function on brown adipocyte differentiation has been poorly understood, which therefore to be investigated in the present study. Mouse embryonic fibroblasts (MEFs) were induced and differentiated to model brown adipocytes, and treated with LXA4 at 0, 1, 5, and 10 nM for 0-14 d. Afterwards, Oil Red O staining detected lipid droplets. In differentiated MEFs with or without LXA4 (10 nM) treatment, western blot and quantitative real-time polymerase chain reaction (qRT-PCR) assessed adipocyte browning marker uncoupling protein 1 (UCP-1), and brown adipogenesis markers peroxisome proliferator-activated receptor gamma (PPARγ), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), cyclooxygenase-2 (COX-2), and positive regulation domain containing 16 (PRDM16) as well as lipogenic genes of stearoyl-CoA desaturase 1 (SCD1), fatty acid synthase (FASN), glucose transporter type 4 (GLUT4), and carbohydrate response element binding protein (ChREBP). The induced differentiation of MEFs toward brown adipocytes was successful. LXA4 promoted intracellular accumulation of lipid droplets of induced cells and increased UCP-1 expression in a dose- or time-dependent manner. Under the administration of LXA4, brown adipogenesis markers and lipogenic genes were further upregulated. LXA4 made a contribution to induce differentiation of MEFs to brown adipocytes, which could be regarded a new drug target for obesity management.

Safety and Preliminary Efficacy of a Novel Host-Modulatory Therapy for Reducing Gingival Inflammation.

Background: Periodontal disease is among the sixth most common inflammatory diseases worldwide with high risk to promote complications from other inflammatory diseases including diabetes, cardiovascular disease and Alzheimer's Disease. Failure of active resolution of inflammation pathways is implicated in pathogenesis of periodontal diseases, including gingivitis. Lipoxin A4 (LXA4), a member of the specialized pro-resolving lipid mediators (SPMs) that drive resolution of inflammation via GPC-receptor mediated pathways, offered therapeutic advantages in preclinical models of periodontitis. Methods: We conducted a randomized, placebo-controlled, parallel-group Phase 1 clinical trial to determine the safety and preliminary efficacy of an LXA4 analog in patients with gingival inflammation. One hundred twenty-seven (127) individuals were randomized to daily use of an oral rinse containing a LXA4 mimetic, methyl ester-benzo-lipoxin A4 (BLXA4), placebo rinse or a no-rinse control group for 28 days. Treatment emergent adverse events (TEAEs) were assessed for safety, the primary outcome. Secondary outcomes included the change in the level of gingival inflammation and periodontal pocket depth (PD). Serum SPMs were monitored using targeted lipid mediator lipidomics to assess potential systemic impact of BLXA4. Results: The frequency of TEAEs was similar in BLXA4 and placebo-treated groups with no study-related SAEs. Once-daily rinsing with BLXA4 for 28-days resulted in a greater decrease in gingival inflammation compared to placebo rinse and no-rinse control groups (mean change: 0.26 GI unit vs 0.21 and 0.17, respectively). PD reduction was also greater with BLXA4 oral rinse compared to placebo and no-rinse groups (mean reduction: 1.23 mm vs. 0.71 mm and 0.46 mm, respectively). Topical application of BLXA4 increased serum levels of SPMs. Conclusion: Treatment with BLXA4 reduces local inflammation, and increases abundance of pro-resolution molecules systemically, which may dampen inflammation that can mediate progression and course of inflammatory diseases beyond periodontitis. Clinical Trial Registration: ClinicalTrials.gov, identifier (NCT02342691).

Role of specialized pro-resolving lipid mediators and their receptors in virus infection: a promising therapeutic strategy for SARS-CoV-2 cytokine storm.

Unexpected viral infections outbreaks, significantly affect human health, leading to increased mortality and life disruption. Among them is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which emerged as a deadly pandemic, calling for intense research efforts on its pathogenicity mechanism and development of therapeutic strategies. In the SARS-CoV-2 cytokine storm, systemic inflammation has been associated with severe illness and mortality. Recent studies have demonstrated special pro-resolving lipids mediators (SPMs) lipoxins, resolvins, maresins, and protectins as potential therapeutic options for abnormal viral-triggered inflammation. Pro-resolving lipids mediators have shown great promise for the treatment of Herpes simplex virus, respiratory syncytial virus, human immunodeficiency virus, and hepatitis C virus. Based on this, studies are being conducted on their therapeutic effects in SARS-CoV-2 infection. In this review, we discussed SPMs and reviewed evidence from recent studies on SPMs as therapeutic options for viral infections, including SARS-CoV2. Based on our analysis of the previous study, we argue that SPMs are a potential treatment for SARS-CoV-2 infection and other viral infections. We expect further research on how SPMs modulate viral-triggered inflammation through G-protein-coupled receptors (GPCRs), and chemical stability and druggability of SPMs.

LXA4 protects against hypoxic-ischemic damage in neonatal rats by reducing the inflammatory response via the IκB/NF-κB pathway.

Hypoxia and the resultant decreases in cerebral blood flow in the perinatal period can lead to neonatal hypoxic-ischemic (HI) brain injury, which can, in turn, cause severe disability or even death. However, the efficacy of current treatment strategies remains limited. Several studies have demonstrated that lipoxin A4 (LXA4), as one of the earliest types of endogenous lipid mediators, can inhibit the accumulation of neutrophils, arrest inflammation, and promote the resolution of inflammation. However, research on LXA4 in the nervous system has rarely been carried out. In the present study, we sought to investigate the protective effect of LXA4 on HI brain damage in neonatal rats, as well as the underlying mechanisms. Through experiments conducted using an HI animal model, we found that the LXA4 intervention promoted the recovery of neuronal function and tissue structure following brain injury while maintaining the integrity of the blood-brain barrier in addition to reducing cerebral edema, infarct volume, and inflammatory responses. Our results suggest that LXA4 interfered with neuronal oxygen-glucose deprivation insults, reduced the expression of inflammatory factors, inhibited apoptosis, and promoted neuronal survival in vitro. Finally, the LXA4 intervention attenuated HI-induced activation of inhibitor kappa B (IκB) and degradation of nuclear factor-κB (NF-κB). In conclusion, our data suggest that LXA4 exerts a neuroprotective effect against neonatal HI brain damage through the IκB/NF-κB pathway. Our findings will help inform future studies regarding the effects of LXA4 on neuroinflammation, blood-brain barrier integrity, and neuronal apoptosis.

The prospective curative role of lipoxin A4 in induced gastric ulcer in rats: Possible involvement of mitochondrial dynamics signaling pathway.

This study purposed to examine the prospective curative role of lipoxin A4 (LXA4 ) in induced gastric ulcer in rats and explore the possible involvement of mitochondrial dynamics signaling pathway. Forty-eight male Wistar rats were divided into four groups: control, indomethacin (IND), IND + omeprazole (IND + Omez), and IND+ LXA4 groups. At the end of the experiment, the gastric pH, gastric fluid volume, total gastric acidity, ulcer index, and curative index were estimated. The gene expression of mitochondrial related protein 1 and mitofusin 2 were determined. In addition, some mitochondrial parameters include mitochondrial transmembrane potential, complex-I activity and reactive oxygen species were measured. Also, some gastric biochemical parameters, histopathological, and immunohistochemical analyses of the gastric mucosa were determined. We found that IND induced gastric ulcer, as manifested by the biochemical, histopathological, and immunohistochemical analyses. Both Omez and LXA4 treatment for 15 days alleviated the IND-induced gastric ulcer as explored by ameliorating the biochemical, histopathological, and immunohistochemical findings. We concluded that LXA4 mitigated the IND-induced gastric ulcer via improving the mitochondrial dynamic imbalance and mitochondrial dysfunction, in addition to its anti-apoptotic, anti-inflammatory, and antioxidant properties.

PUFAs, BDNF and lipoxin A4 inhibit chemical-induced cytotoxicity of RIN5F cells in vitro and streptozotocin-induced type 2 diabetes mellitus in vivo.

OBJECTIVE: To study whether minimal doses of arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and lipoxin A4 (LXA4) and brain-derived neurotrophic factor (BDNF), when used in combination can protect RIN5F cells from chemical-induced cytotoxicity. As a corollary, to know whether plasma BDNF and LXA4 are altered in STZ-induced type 2 DM animals. MATERIALS AND METHODS: RIN5F cells, alloxan (AL), streptozotocin (STZ), doxorubicin (DB), and benzo(a)pyrene (BP) were used in this study. Chemical-induced apoptosis and changes in antioxidants, lipid peroxides and nitric oxide (NO) and LXA4 and BDNF levels in RIN5F cells were studied. Alterations in plasma concentrations of BDNF and LXA4 in STZ-induced type 2 diabetes animals was estimated. RESULTS: BDNF, LXA4 and AA, EPA and DHA protected (P < 0.001 and P < 0.01 respectively) against AL/STZ/DB/BP-induced toxicity to RIN5F cells in vitro. AL/ STZ/DB/BP inhibited BDNF and LXA4 production by RIN5F cells and were restored to normal by AA, EPA and DHA. Sub-optimal doses of BDNF, LXA4, AA and EPA when used in combination protected against cytotoxic action of AL/STZ/DB/BP on RIN5F cells in vitro by restoring LXA4/BDNF levels and altered antioxidant/lipid peroxides/NO levels (P < 0.01) to normal. STZ (65 mg/kg)-induced type 2 diabetes mellitus animals showed reduced plasma BDNF and LXA4 levels (P < 0.001). DISCUSSION: AL/STZ/DB/BP-induced cytotoxicity to RIN5F cells in vitro can be prevented by BDNF, LXA4 and AA. AL/STZ/DB/BP are cytotoxic, possibly, by suppressing the production of LXA4 and BDNF in RIN5F cells. STZ-induced type 2 DM animals have decreased plasma levels of LXA4 and BDNF. CONCLUSION: The results of the present study suggest that BDNF, LXA4, EPA, DHA, AA, GLA and BDNF protect pancreatic ß cells from the cytotoxic action of various chemicals and prevent development of diabetes mellitus. LXA4 seems to be the mediator of these cytoprotective actions of BDNF and PUFAs suggesting a close interaction exists among these molecules (BDNF, PUFAs and LXA4). Hence, methods developed to deliver a combination of PUFAs (especially AA), LXA4 and BDNF may prevent development of diabetes mellitus (both type 1 and type 2).

Effects of Lipoxin A4 Pretreatment on Cognitive Function of Aged Rats after Global Cerebral Ischemia Reperfusion.

The aim of the present study was to investigate the effect of lipoxin A4 (LXA4) pretreatment on cognitive function of aged rats after global cerebral ischemia reperfusion, and to explore its possible mechanism. Thirty-six aged male Sprague-Dawley rats were randomly divided into three groups (n=2 each): sham-operation group (S group), global cerebral ischemia reperfusion group (I/R group) and LXA4-pretreatment group (L group). The rat model of global cerebral ischemia reperfüsion was established by occlusion of the bilateral common carotid artery with hypotension. The cognitive function of rats was determined by a step-down type passive avoidance test and Morris Water Maze test on the third day after reperfUsion. Rats were sacrificed after Water Maze test and the pathological changes of hippocampal CAI region were observed and the related inflammatory mediators were determined. As compared with S group, the escape latency in I/R group was prolonged from the first day to the fifth day, while that in L group was prolonged from the first day to the third day. The retention time in I/R group and L group in the first quadrant was shortened. The reaction time, frequency of reaction mistake and frequency of escape mistake in I/R group increased, and the latent period shortened. The frequency of escape mistake in L group increased, and the damage in the hippocampal CAI region of I/R group and L group was obvious. The levels of S-100ß, TNP-α, IL-lß, IL-10 and NF-κB in I/R group and L group increased. As compared with I/R group, the escape latency in L group was shortened from the first day to the fifth day, and the retention time in the first quadrant prolonged. The reaction time, frequency of reaction mistake and frequency of escape mistake in L group decreased, and the latent period prolonged. The damage in the hippocampal CAI region of L group was alleviated as well. The levels of S-100ß, TNP-α, IL-lß and NF-κB in L group decreased, and those of IL-10 increased. It can be concluded that LXA4 pretreatment can improve the cognitive function in aged rats after global cerebral ischemia reperfusion probably by inhibiting the inflammatory reaction.

[Effect of lipoxin A4 on the expression of Toll-like receptor 4 and TNF receptor-associated factor 6 in the liver of obese rats with sepsis].

OBJECTIVE: To study the protective effect of lipoxin A4 (LXA4) against sepsis induced by lipopolysaccharide (LPS) in rats with obesity and its effect on the expression of Toll-like receptor 4 (TLR4) and TNF receptor-associated factor 6 (TRAF6) in the liver. METHODS: A total of 60 male Sprague-Dawley rats aged three weeks were randomly divided into a normal group and an obesity group, with 30 rats in each group. A rat model of obesity was established by high-fat diet. Each of the two groups was further randomly divided into control group, sepsis group, and LXA4 group, and 8 rats were selected from each group. The rats in the control, sepsis, and LXA4 groups were treated with intraperitoneal injection of normal saline, LPS, and LXA4+LPS respectively. Twelve hours later, blood samples were collected from the heart and liver tissue samples were also collected. ELISA was used to measure the serum levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Western blot was used to measure the protein expression of TLR4 and TRAF6 in liver tissue. Quantitative real-time PCR was used to measure the mRNA expression of TLR4 and TRAF6. RESULTS: After being fed with high-fat diet for 6 weeks, the obesity group had significantly higher average weight and Lee's index than the normal group (P<0.05). Compared with the normal group, the obesity group had significant increases in the serum levels of IL-6 and TNF-α (P<0.05). In the normal group or the obesity group, the sepsis subgroup had significant increases in the serum levels of IL-6 and TNF-α compared with the control subgroup (P<0.05), while the LXA4 subgroup had significant reductions in the two indices compared with the sepsis subgroup (P<0.05). Compared with the normal group, the obesity group had significant increases in the protein and mRNA expression of TLR4 and TRAF6 (P<0.05). In the normal group or the obesity group, the sepsis subgroup had significant increases in the protein and mRNA expression of TLR4 and TRAF6 compared with the control subgroup (P<0.05). Compared with the sepsis subgroup, the LXA4 subgroup had significant reductions in the protein and mRNA expression of TLR4 and TRAF6 (P<0.05). CONCLUSIONS: LXA4 can reduce the serum levels of IL-6 and TNF-α and alleviate inflammatory response. LXA4 can inhibit the expression of TLR4 and TRAF6 in the liver of septic rats, possibly by inhibiting the TLR4 signaling pathway.

Reprogramming tumor stroma using an endogenous lipid lipoxin A4 to treat pancreatic cancer.

Pancreatic stellate cells (PSCs) are the precursors of cancer-associated fibroblasts (CAFs), which potentiate pancreatic tumor growth and progression. In this study, we investigated whether Lipoxin A4 (LXA4), an endogenous bioactive lipid, can inhibit the differentiation of human PSCs (hPSCs) into CAF-like myofibroblasts and thereby hPSC-induced pro-tumorigenic effects. LXA4 significantly inhibited TGF-ß-mediated differentiation of hPSCs by inhibiting pSmad2/3 signalling. Furthermore, treatment with LXA4 abolished the paracrine effects (proliferation and migration of Panc-1 tumor cells) of hPSCs in vitro. These data demonstrated that LXA4 can interrupt pro-tumoral paracrine signalling of hPSCs. Furthermore, LXA4 treatment significant decreased the size and growth rate of 3D-heterospheroids comprised of hPSC and Panc-1 and these effects were exhibited due to inhibition of hPSC-induced collagen1 expression. In vivo, we examined the therapeutic efficacy of LXA4 in a co-injection (Panc-1 and hPSCs) subcutaneous tumor model. Intriguingly, LXA4 significantly abolished the tumor growth (either injected intratumor or intraperitoneally), attributed to a significant reduction in fibrosis, shown with collagen1 expression. Altogether, this study proposes LXA4 as a potent inhibitor for hPSCs which can be applied to reprogram tumor stroma in order to treat pancreatic cancer.

Combined administration of resolvin E1 and lipoxin A4 resolves inflammation in a murine model of Alzheimer's disease.

Dysfunction in the resolution of inflammation may play a key role in Alzheimer's disease (AD). In this study, we found that the levels of specialized pro-resolving lipid mediators (SPMs) in the hippocampus of 5xFAD mice are significantly lower than in non-transgenic littermates. We, therefore, tested the hypothesis that treatment with resolvin E1 (RvE1) and lipoxin A4 (LXA4) alone or in combination will reverse the neuroinflammatory process and decrease Aß pathology. 5xFAD mice were treated intraperitoneally starting at 1month of age with RvE1 or LXA4 alone or in combination at a dose of 1.5 µg/kg, 3 times a week until 3months of age. We found that treatment with RvE1 or LXA4 alone or in combination increased the concentration of RvE1, LXA4, and RvD2 in the hippocampus as measured by ELISA. Combination treatment of RvE1 and LXA4 had a more potent effect on the activation of microglia and astrocytes than either treatment alone, measured by immunohistochemistry with Iba1 and GFAP antibodies, respectively. The concentrations of Aß40 and Aß42 were measured by ELISA and the percentage of Aß plaques were analyzed by immunohistochemistry. All treatments single and in combination, decreased the measures of Aß pathology and restored the homeostasis reversing the inflammatory process for inflammatory cytokines and chemokines (GM-CSF, IFN-γ, IL-1ß, IL-6, IL-10, TNF-α, MCP-1, MIP-1α, MIP-1ß, and RANTES) as measured by multiplex immunoassay. Overall, the study showed that the levels of SPMs in the hippocampus of 5xFAD mice were significantly lower than in wild-type mice; that treatment with RvE1 and LXA4 restored the level of these compounds, reversed the inflammatory process, and decreased the neuroinflammation associated with Aß pathology in 5xFAD mice.

Resolution Agonist 15-epi-Lipoxin A4 Programs Early Activation of Resolving Phase in Post-Myocardial Infarction Healing.

Following myocardial infarction (MI), overactive inflammation remodels the left ventricle (LV) leading to heart failure coinciding with reduced levels of 15-epi-Lipoxin A4 (15-epi LXA4). However, the role of 15-epi LXA4 in post-MI acute inflammatory response and resolving phase is unclear. We hypothesize that liposomal fusion of 15-epi-LXA4 (Lipo-15-epi-LXA4) or free 15-epi-LXA4 will expedite the resolving phase in post-MI inflammation. 8 to 12-week-old male C57BL/6 mice were subjected to permanent coronary artery ligation. Lipo-15-epi-LXA4 or 15-epi-LXA4 (1 µg/kg/day) was injected 3 hours post-MI for (d)1 or continued daily till d5. 15-epi-LXA4 activated formyl peptide receptor (FPR2) and GPR120 on alternative macrophages but inhibited GPR40 on classical macrophages in-vitro. The 15-epi-LXA4 injected mice displayed reduced LV and lung mass to body weight ratios and improved ejection fraction at d5 post-MI. In the acute phase of inflammation-(d1), 15-epi-LXA4 primes neutrophil infiltration with a robust increase of Ccl2 and FPR2 expression. During the resolving phase-(d5), 15-epi-LXA4 initiated rapid neutrophils clearance with persistent activation of FPR2 in LV. Compared to MI-control, 15-epi-LXA4 injected mice showed reduced renal inflammation along with decreased levels of ngal and plasma creatinine. In summary, 15-epi-LXA4 initiates the resolving phase early to discontinue inflammation post-MI, thereby reducing LV dysfunction.

Lipoxin A4, a 5-lipoxygenase pathway metabolite, modulates immune response during acute respiratory tularemia.

Respiratory infection with Francisella tularensis (Ft) is characterized by a muted, acute host response, followed by sepsis-like syndrome that results in death. Infection with Ft establishes a principally anti-inflammatory environment that subverts host-cell death programs to facilitate pathogen replication. Although the role of cytokines has been explored extensively, the role of eicosanoids in tularemia pathogenesis is not fully understood. Given that lipoxin A4 (LXA4) has anti-inflammatory properties, we investigated whether this lipid mediator affects host responses manifested early during infection. The addition of exogenous LXA4 inhibits PGE2 release by Ft-infected murine monocytes in vitro and diminishes apoptotic cell death. Tularemia pathogenesis was characterized in 5­lipoxygenase-deficient (Alox5-/-) mice that are incapable of generating LXA4 Increased release of proinflammatory cytokines and chemokines, as well as increased apoptosis, was observed in Alox5-/- mice as compared with their wild-type counterparts. Alox5-/- mice also exhibited elevated recruitment of neutrophils during the early phase of infection and increased resistance to lethal challenge. Conversely, administration of exogenous LXA4 to Alox5-/- mice made them more susceptible to infection thus mimicking wild-type animals. Taken together, our results suggest that 5-LO activity is a critical regulator of immunopathology observed during the acute phase of respiratory tularemia, regulating bacterial burden and neutrophil recruitment and production of proinflammatory modulators and increasing morbidity and mortality. These studies identify a detrimental role for the 5-LO-derived lipid mediator LXA4 in Ft-induced immunopathology. Targeting this pathway may have therapeutic benefit as an adjunct to treatment with antibiotics and conventional antimicrobial peptides, which often have limited efficacy against intracellular bacteria.

Immobilization and delivery of biologically active Lipoxin A4 using electrospinning technology.

Lipoxin (LX)A4 is a lipoxygenase-formed arachidonic acid metabolite with potent anti-inflammatory, pro-resolution properties. Its therapeutic efficacy has been largely demonstrated in a variety of cellular, preclinical and clinical models. Among these, periodontal disease, where LXA4 promotes tissue repair, also by modulating functions of human periodontal ligament stem cells (hPDLSCs). As medicated biomembranes may be particularly useful in clinical settings, where local stimulation of tissue repair is needed, we used electrospinning to embed LXA4 in membranes made of poly(ethylene oxide) (PEO) and poly(d,l-lactide) (PDLLA). These membranes were fully characterized by scanning electron microscopy, differential scanning calorimetry and biocompatibility with hPDLSCs. Here, we report that LXA4 is retained in these membranes and that ∼15-20% of the total LXA4 amount added to the reaction can be eluted from the membranes using an aqueous buffered medium. The eluted LXA4 fully retained its capability to stimulate hPDLSC proliferation. A similar effect was obtained by adding directly the LXA4-containing membranes to cells. These results demonstrate for the first time that LXA4 can be incorporated into biomembranes, which may be useful to combat local inflammation and promote tissue repair in selected clinical settings.

Lipoxin A4 inhibits microglial activation and reduces neuroinflammation and neuropathic pain after spinal cord hemisection.

BACKGROUND: Spinal cord injury (SCI) is a severe neurological disorder with many disabling consequences, including persistent neuropathic pain, which develops in about 40 % of SCI patients and is induced and sustained by excessive and uncontrolled spinal neuroinflammation. Here, we have evaluated the effects of lipoxin A4 (LXA4), a member of a unique class of endogenous lipid mediators with both anti-inflammatory and analgesic properties, on spinal neuroinflammation and chronic pain in an experimental model of SCI. METHODS: Spinal hemisection at T10 was carried out in adult male CD1 mice and Wistar rats. To test if LXA4 can reduce neuroinflammation and neuropathic pain, each animal received two intrathecal injections of LXA4 (300 pmol) or vehicle at 4 and 24 h after SCI. Sensitivity to mechanical stimulation of the hind paws was evaluated using von Frey monofilaments, and neuroinflammation was tested by measuring the mRNA and/or protein expression levels of glial markers and cytokines in the spinal cord samples after SCI. Also, microglia cultures prepared from murine cortical tissue were used to assess the direct effects of LXA4 on microglial activation and release of pro-inflammatory TNF-α. RESULTS: LXA4 treatment caused significant reductions in the intensity of mechanical pain hypersensitivity and spinal expression levels of microglial markers and pro-inflammatory cytokines induced by SCI, when compared to rodents receiving control vehicle injections. Notably, the increased expressions of the microglial marker IBA-1 and of the pro-inflammatory cytokine TNF-α were the most affected by the LXA4 treatment. Furthermore, cortical microglial cultures expressed ALX/FPR2 receptors for LXA4 and displayed potentially anti-inflammatory responses upon challenge with LXA4. CONCLUSIONS: Collectively, our results suggest that LXA4 can effectively modulate microglial activation and TNF-α release through ALX/FPR2 receptors, ultimately reducing neuropathic pain in rodents after spinal cord hemisection. The dual anti-inflammatory and analgesic properties of LXA4, allied to its endogenous nature and safety profile, may render this lipid mediator as new therapeutic approach for treating various neuroinflammatory disorders and chronic pain with only limited side effects.

Suplementos dietarios en periodoncia: revisión bibliográfica narrativa / Additives in periodontics: a narrative review of the literature

Se realizó la revisión de los trabajos de investigación relacionados con la utilización de resolvinas y probióticos como complementos dietarios en la terapia periodontal, tanto en animales de experimentación como en humanos, describiendo el origen, la composición y los posibles mecanismos de acción. A partir de los trabajos revisados, se concluyó que las aludidas sustencias son, en la actualidad, un tema de investigación no traspolable a la clínica y que en el mediano plano, podrían potenciar las terapias actuales para patologías periodontales específicas.

Lipoxin A4 attenuates LPS-induced mouse acute lung injury via Nrf2-mediated E-cadherin expression in airway epithelial cells.

A fundamental element of acute lung injury (ALI) is the inflammation that is part of the body's immune response to a variety of local or systemic stimuli. Lipoxins (LXs) are important endogenous lipids that mediate resolution of inflammation. Previously, we demonstrated that LXA4 reduced the LPS inhalation-induced pulmonary edema, neutrophil infiltration and TNF-α production in mice. With the same model, the current investigation focused on the role of the airway epithelium, a first-line barrier and a prime target of inhaled toxicants. We report that LXA4 strongly inhibited LPS-induced ALI in mice, in part by protecting the airway epithelium and preserving the E-cadherin expression and airway permeability. Using a cryo-imaging assay and fluorescence detection, LXA4 was shown to block LPS-induced ROS generation and preserve mitochondrial redox status both in vivo and in vitro. To further assess whether and how NF-E2-related factor 2 (Nrf2) was involved in the protective effect of LXA4, fluorescence resonance energy transfer (FRET) analysis was employed in human epithelial cell line (16HBE), to determine the relative distance between Nrf2 and its negative regulator or cytosolic inhibitor, Kelch-like ECH-associated protein 1 (Keap1). It provided us the evidence that LXA4 further promoted the dissociation of Nrf2 and Keap1 in LPS-treated 16HBE cells. The results also showed that LXA4 activates Nrf2 by phosphorylating it on Ser40 and triggering its nuclear translocation. Moreover, when the plasmid expression dominant negative mutation of Nrf2 was transfected as an inhibitor of wild-type Nrf2, the protective effect of LXA4 on E-cadherin expression was almost completely blocked. These results provide a new mechanism by which LXA4 inhibits LPS-induced ALI through Nrf2-mediated E-cadherin expression.

Early single Aspirin-triggered Lipoxin blocked morphine anti-nociception tolerance through inhibiting NALP1 inflammasome: Involvement of PI3k/Akt signaling pathway.

Clinical usage of opioids in pain relief is dampened by analgesic tolerance after chronic exposure, which is related to opioid-associated neuroinflammation. In the current study, which is based on a chronic morphine tolerance rat model and sustained morphine treatment on primary neuron culture, it was observed that Akt phosphorylation, cleaved-Caspase-1-dependent NALP1 inflammasome activation and IL-1ß maturation in spinal cord neurons were significantly enhanced by morphine. Moreover, treatment with LY294002, a specific inhibitor of PI3k/Akt signaling, significantly reduced Caspase-1 cleavage, NALP1 inflammasome activation and attenuated morphine tolerance. Tail-flick tests demonstrated that pharmacological inhibition on Caspase-1 activation or antagonizing IL-1ß dramatically blocked the development of morphine tolerance. The administration of an exogenous analogue of lipoxin, Aspirin-triggered Lipoxin (ATL), caused a decline in Caspase-1 cleavage, inflammasome activation and mature IL-1ß production and thus attenuated the development of morphine tolerance by inhibiting upstream Akt phosphorylation. Additionally, treatment with DAMGO, a selective µ-opioid receptor peptide, significantly induced Akt phosphorylation, Caspase-1 cleavage and anti-nociception tolerance, all of which were attenuated by ATL treatment. Taken together, the present study revealed the involvement of spinal NALP1 inflammasome activation in the development of morphine tolerance and the role of the µ-receptor/PI3k-Akt signaling/NALP1 inflammasome cascade in this process. By inhibiting this signaling cascade, ATL blocked the development of morphine tolerance.

Effects of Lipoxin A4 on antimicrobial actions of neutrophils in sepsis.

In sepsis, hyperactivation of neutrophils can lead to tissue injury. Later, neutrophil dysregulation with reduced levels of migration, decreased apoptosis and inadequate phagocytosis may impair the host׳s ability to clear infection. Lipoxin A4 (LXA4) is a pro-resolution lipid mediator which reduces neutrophil migration and inflammatory mediator expression. As neutrophil migration and activation are important in bacterial clearance, the role of LXA4 in regulating neutrophil function for bacterial clearance is unclear. Using the cecal ligation and puncture (CLP) rat model of sepsis, LXA4 given after 1h reduced blood bacterial load at 24h. LXA4 treatment decreased neutrophil migration to the peritoneum but augmented blood neutrophil phagocytic ability and promoted apoptosis without affecting free radical production. In contrast, LXA4 increased peritoneal neutrophil phagocytic ability without affecting apoptosis or free radical production suggesting that in vivo effects of LXA4 were compartment specific. To investigate if LXA4 acted directly on neutrophils, blood and peritoneal leukocytes were taken from CLP rats 1h after surgery and incubated ex vivo with and without LXA4. LXA4 (1nM) increased phagocytosis in blood neutrophils without affecting apoptosis or free radical production. Ex vivo LXA4 had no effect on peritoneal neutrophils which suggests that LXA4 enhanced peritoneal neutrophil phagocytic ability in vivo by an indirect mechanism. The results suggest that LXA4 reduced neutrophil migration, but increased neutrophil bacteria clearing function without excessive free radical production. This phenotype was associated with reduced blood bacteria load.

Aspirin-triggered Lipoxin A4 attenuates mechanical allodynia in association with inhibiting spinal JAK2/STAT3 signaling in neuropathic pain in rats.

Aspirin-triggered Lipoxin A4 (ATL), as a Lipoxin A4 (LXA4) epimer, is endogenously produced by aspirin-acetylated cycloxygenase-2 (COX-2) and plays a vital role in endogenous anti-inflammation via the LXA4 receptor (ALX). Recent investigations have indicated that spinal neuroinflammation and the activation of the Janus Kinase 2 (JAK2)/Signal Transducers and Transcription Activators 3 (STAT3) signaling pathway are involved in neuropathic pain states. However, the effect of ATL on neuroinflammation and JAK2/STAT3 signaling in chronic constriction injury (CCI)-induced neuropathic pain in rats has not been well-studied. The present study demonstrated the anti-inflammatory and analgesic effect of ATL on neuropathic pain and assessed the role of spinal JAK2/STAT3 signaling on the effect of ATL. Intrathecal administration of ATL significantly attenuated mechanical allodynia via spinal ALX and inhibited the upregulation of pro-inflammatory cytokines (IL-1ß, IL-6, and TNF-α) on day 7 of CCI surgery. In addition, ATL markedly suppressed the upregulation of p-STAT3 induced by the neuropathic pain. Blockade of JAK2-STAT3 signaling with intrathecal administration of the JAK2 inhibitor AG490 or the STAT3 inhibitor S3I-201 clearly reduced mechanical allodynia and the upregulation of pro-inflammatory cytokines in CCI rats. Interestingly, inhibition of JAK2/STAT3 signaling via ATL or the specific signaling inhibitor (AG49, S3I-201) further promoted the increased expression of suppressor of cytokine signaling 3 (SOCS3) mRNA in the spinal cord induced by CCI surgery. Taken together, our results suggested that the analgesic effect of ATL was mediated by inhibiting spinal JAK2/STAT3 signaling and hence the spinal neuroinflammation in CCI rats.