Altered inflammatory responses in leukotriene-deficient mice

Recent advances in function and structure of two leukotriene B4 receptors: BLT1 and BLT2

Leukotriene B₄ (LTB₄) is generated by the enzymatic oxidation of arachidonic acid, which is then released from the cell membrane and acts as a potent activator of leukocytes and other inflammatory cells. Numerous studies have demonstrated the physiological and pathophysiological significance of this lipid in various diseases. LTB₄ exerts its activities by binding to its specific G protein-coupled receptors (GPCRs): BLT1 and BLT2. In mouse disease models, treatment with BLT1 antagonists or BLT1 gene ablation attenuated various diseases, including bronchial asthma, arthritis, and psoriasis, whereas BLT2 deficiency exacerbated several diseases in the skin, cornea, and small intestine. Therefore, BLT1 inhibitors and BLT2 activators could be beneficial for the treatment of several inflammatory and immune disorders. As a result, attractive compounds targeting LTB₄ receptors have been developed by several pharmaceutical companies. This review aims to understand the potential of BLT1 and BLT2 as therapeutic targets for the treatment of various inflammatory diseases. In addition, recent topics are discussed with major focuses on the structure and post-translational modifications of BLT1 and BLT2. Collectively, current evidence on modulating LTB₄ receptor functions provides new strategies for the treatment of various diseases.

Phytochemical evaluation of Cucumis prophetarum: protective effects against carrageenan-induced prostatitis in rats

Phytochemical study of the MeOH extract of Cucumis prophetarum fruits (family Cucurbitaceae) by using different chromatographic techniques led to the isolation of three metabolites; spinasterol (1), cucurbitacin B (2), and 2-O-β-D-glucopyranosylcucurbitacin E (3). Their chemical structures were created on the basis of physical, chemical, spectroscopic data 1D (¹H and ¹³C NMR), and 2D NMR (HSQC and HMBC), as well as similarity with literature data. Cucurbitacin B (Cu-B) (2) was found to be the major constituent. Potential protective activities of MeOH extract, CHCl₃, and EtOAc fractions and Cu-B were evaluated against carrageenan-induced prostatic inflammation in rats. Acute toxicity was assessed by evaluating LD₅₀. Pretreatment with CHCl₃ fraction and Cu-B ameliorated the rise in the prostate index and obviously protected against histopathological changes. Further, MeOH, extract, CHCl₃, and EtOAc fractions as well as Cu-B significantly protected against oxidative stress in prostatic tissues. The anti-inflammatory activities of the extract, fractions and Cu-B were confirmed by ameliorating the rise in prostatic content of the inflammatory mediators TNF-α, IL-1β, COX-2, and iNOS induced by carrageenan. In addition, the rise in the chemotactic factors were myeloperoxidase (MPO), F4-80, and monocyte chemoattractant protein-1 (MCP-1) was significantly hampered. In conclusion, three known compounds (1-3) were isolated from Cucumis prophetarum fruits. Cu-B (2) was the major identified compound. Particularly, CHCl₃ fraction and isolated Cu-B exhibited potent anti-inflammatory activity against carrageenan-induced prostatitis. The anti-inflammatory activity can be attributed, at least partly, to inhibition of neutrophil and macrophage infiltration into prostatic tissues.

Central leukotrienes modulate fever tolerance to LPS in rats

Leukotrienes mediate several inflammatory events such as neutrophil chemoattraction, leukocyte adhesion, and central-release of cytokines and fever. However, there is no information available about their putative role in lipopolysaccharide (LPS) tolerance. The rational of the present study was to find out if central leukotrienes are involved in the development of LPS tolerance. Thus, we inhibited central leukotriene synthesis in tolerant rats using a pharmacological tool, i.e., a selective inhibitor of leukotriene synthesis MK-886 injected into the third ventricle (3V) of rats. Body core temperature (Tb) was measured using a datalogger placed inside the abdominal cavity. A low-dose of LPS (100 μg/kg ip) was given for 4 consecutive days to induce LPS tolerance. At day 4, rats received a microinjection of MK-886 into the 3V immediately before LPS, whereas control groups were treated with vehicle (saline). We observed that LPS failed to induce plasma cytokines surges, increased hypothalamic PGE₂ levels and fever 3 days post LPS treatment, aptly characterizing the tolerance. When MK-886 was given to control rats treated with saline, no significant change in Tb was observed. However, a full LPS-induced fever was observed in tolerant rats pretreated with MK-886, which was associated with an enhancement in the hypothalamic PGE₂ levels, that were not accompanied by plasma cytokines (IL-1β, and IL-6) and PGE₂ surges. These data are consistent with the notion that central leukotrienes play a role in fever tolerance to LPS.

Treatment with either COX-2 inhibitor or 5-LOX inhibitor causes no compensation between COX-2 pathway and 5-LOX pathway in chronic aluminum overload-induced liver injury in rats

This study was designed to observe the compensation between cyclooxygenase-2 pathway and 5-lipoxygenase pathway in chronic aluminum overload-induced liver injury rats. A rat hepatic injury model of chronic aluminum injury was established by the intragastric administration of aluminum gluconate (Al3 + 200 mg/kg per day, 5 days a week for 20 weeks). The COX-2 inhibitor [meloxicam (1 mg/kg)] and 5-LOX inhibitor [caffeic acid (30 mg/kg)] were intragastrically administered 1 h after aluminum administration. The histopathology was detected by hematoxylin-eosin staining. A series of biochemical indicators were measured with biochemistry assay or ELISAs. The expressions of COX-2 and 5-LOX were measured by immunohistochemistry. Our experimental results showed that aluminum overload caused a significant damage to the liver and also significantly increased the expressions of COX-2, 5-LOX and the levels of inflammation and oxidative stress. The administration of meloxicam and caffeic acid significantly protected livers against histopathological injury, significantly decreased plasma ALT, AST, and ALP levels, significantly decreased TNF-α, IL-6, IL-1β levels, and oxidative stress. However, the administration of caffeic acid did not significantly increase the expression of COX-2 compared with the model group. On the other hand, the administration of meloxicam also did not significantly increase the expression of 5-LOX compared with the model group. Our results indicate that there is no compensation between COX-2 pathway and 5-LOX pathway by inhibiting either COX-2 or 5-LOX in chronic aluminum overload-induced liver injury rat.

LOX inhibitor HOEC interfered arachidonic acid metabolic flux in collagen-induced arthritis rats

Arachidonic acid (AA) metabolic network generates a variety of products that mediate or modulate inflammatory reactions. (+)-2-(1-hydroxyl-4-oxocyclohexyl) ethyl caffeate (HOEC), isolated from Incarvillea mairei var. granditlora (Wehrhahn) Grierson, was found as an inhibitor of 5-LOX and 15-LOX in vitro. When evaluated in collagen-induced arthritis (CIA) rats, however, lowdose of HOEC (1 mg/kg) showed better efficacy than that of high dose (10 mg/kg). To study how HOEC interfered the AA metabolic pathway, in this study, we dynamically observed the changes of plasma AA metabolites (LTB4, LTC4, 15-HETE, PGE2, TXB2 and PGD2) in the CIA rats treated with different doses of HOEC by using enzyme-linked immunosorbent assay (ELISA). The results showed that eicosanoids were elevated synchronously at three time points in different treated rats. The incidence of arthritis had a higher correlation with LOX pathway while the COX pathway might be more important in the severity of arthritis. HOEC in all doses could inhibit LOX pathway in the beginning of arthritis while highdose of HOEC could induce the increase of COX metabolites in the later stage of disease. These dynamic changes of eicosanoids, depending on the regulation of metabolic flux, can be interfered by HOEC and thus affect the output of efficacy.

miR-146a suppresses 5-lipoxygenase activating protein (FLAP) expression and Leukotriene B4 production in lung cancer cells

Arachidonic acid (AA) can be converted into prostaglandins (PGs) or leukotrienes (LTs) by the enzymatic actions of cyclooxygenases (COX-1 and COX-2) or 5-lipoxygenase (5-LO), respectively. PGs and LTs are lipid signaling molecules that have been implicated in various diseases, including multiple cancers. 5-LO and its activating protein (FLAP) work together in the first two conversion steps of LT production. Previous work has suggested a role for LTs in cancer development and progression. MicroRNAs (miRNAs) are small RNA molecules that negatively regulate gene expression post-transcriptionally, and have previously been shown to be involved in cancer. Here, we show that high FLAP expression is associated with lower overall survival in lung adenocarcinoma patients, and FLAP protein is overexpressed in lung cancer cells compared to normal lung cells. Our lab has previously shown that miR-146a regulates COX-2 in lung cancer cells, and this miRNA is also predicted to target FLAP. Transient and stable transfections of miR-146a repress endogenous FLAP expression in lung cancer cells, and reporter assays show this regulation occurs through a direct interaction between the FLAP 3′ untranslated region (UTR) and miR-146a. Restoration of miR-146a also results in decreased cancer cell Leukotriene B4 (LTB₄) production. Additionally, methylation analysis indicates the miR-146a promoter is hypermethylated in lung cancer cell lines. Taken together, this study and previous work from our lab suggest miR-146a is an endogenous dual inhibitor of AA metabolism in lung cancer cells by regulating both PG and LT production through direct targeting of the COX-2 and FLAP 3’ UTRs.

The hidden mechanism beyond ginger (Zingiber officinale Rosc.) potent in vivo and in vitro anti-inflammatory activity

ETHNOPHARMACOLOGICAL RELEVANCE

Ginger (Zingiber officinale Roscoe) is a well known anti-inflammatory drug in the Egyptian, Indian and Chinese folk medicines, yet its mechanism of action is unclear.

AIM OF THE STUDY

To explore its mechanism of action and to correlate it to its biophytochemicals.

MATERIALS AND METHODS

Various extracts viz. water, 50%, 70%, 80%, and 90% ethanol were prepared from ginger rhizomes. Fractionation of the aqueous extract (AE) was accomplished using Diaion HP-20. In vitro anti-inflammatory activity of the different extracts and isolated compounds was evaluated using protein denaturation inhibition, membrane stabilization, protease inhibition, and anti-lipoxygenase assays. In vivo anti-inflammatory activity of AE was estimated using carrageenan-induced rat paw edema in rats at doses 25, 50, 100 and 200mg/kg b.wt.

RESULTS

All the tested extracts showed significant (p< 0.1) in vitro anti-inflammatory activities. The strongest anti-lipoxygenase activity was observed for AE that was more significant than that of diclofenac (58% and 52%, respectively) at the same concentration (125μg/ml). Purification of AE led to the isolation of 6-poradol (G1), 6-shogaol (G2); methyl 6- gingerol (G3), 5-gingerol (G4), 6-gingerol (G5), 8-gingerol (G6), 10-gingerol (G7), and 1-dehydro-6-gingerol (G8). G1, G2 and G8 exhibited potent activity in all the studied assays, while G4 and G5 exhibited moderate activity. In vivo administration of AE ameliorated rat paw edema in a dose-dependent manner. AE (at 200mg/kg) showed significant reduction in production of PGE2, TNF-α, IL-6, monocyte chemoattractant protein-1 (MCP-1), regulated upon activation, normal T-cell expressed and secreted (RANTES), myeloperoxidase (MPO) activity by 60%, 57%, 60%, 41%, 32% and 67%, respectively. AE at 100 and 200mg/kg was equipotent to indomethacin in reduction of NOx level and in increasing the total antioxidant capacity (TAC). Histopathological examination revealed very few inflammatory cells infiltration and edema after administration of AE (200mg/kg) prior to carrageenan.

CONCLUSIONS

Ginger anti-inflammatory activity is mediated by inhibiting macrophage and neutrophils activation as well as negatively affecting monocyte and leukocyte migration. This was evidenced by the dose-dependent decrease in pro-inflammatory cytokines and chemokines and replenishment the total antioxidant capacity.

Leptin Mediates In Vivo Neutrophil Migration: Involvement of Tumor Necrosis Factor-Alpha and CXCL1

Leptin directly activates macrophages and lymphocytes, but the role of leptin in neutrophil activation and migration is still controversial. Here, we investigate the in vivo mechanisms of neutrophil migration induced by leptin. The intraperitoneal injection of leptin (1 mg/kg) induces a time- and concentration-dependent neutrophil influx. We did not observe the enhancement of lipid bodies/droplets in neutrophils, after leptin treatment, as we had observed previously in peritoneal macrophages. The participation of leukotriene B₄ (LTB₄) in neutrophil recruitment triggered by leptin was investigated using different strategies. Leptin-induced neutrophil recruitment occurs both in the absence of 5-lipoxygenase activity in 5-lipoxygenase (5-LO)^-/- mice and after the administration of either 5-LO inhibitor (Zileuton) or the LTB₄ receptor antagonist (U-75302). Moreover, no direct induction of LTB₄ by leptin could be observed. Neutrophil influx could not be prevented by the mammalian target of rapamycin (mTOR) inhibitor, rapamycin, contrasting with the leptin-induced signaling for lipid body formation in macrophage that is mTOR-dependent. Leptin administration led to tumor necrosis factor-alpha (TNFα) production by the peritoneal cells both in vivo and in vitro. In addition, neutrophil recruitment was inhibited in tumor necrosis factor receptor 1 (TNFR1^-/-) mice, indicating a role for TNF in leptin-induced neutrophil recruitment to the peritoneal cavity. Leptin-induced neutrophil influx was PI3Kγ-dependent, as it was absent in PI3Kγ^-/- mice. Accordingly, leptin induced the peritoneal cells to produce CXCL1, both in vivo and in vitro, and the neutrophil influx was ablated after using an antibody against CXCL1. Our results establish TNFα/TNFR1- and CXCL1-dependent signaling as important pathways for leptin-induced neutrophil migration in vivo.

Inhibition of 5-lipoxygenase attenuates inflammation and BONE resorption in lipopolysaccharide-induced periodontal disease

BACKGROUND

Arachidonate-5-lipoxygenase (5-LO) activity and increased leukotriene B4 (LTB4) production have been implicated in various inflammatory conditions. Increased production of leukotrienes has been associated with periodontal diseases; however, their relative contribution to tissue destruction is unknown. In this study, an orally active specific 5-LO inhibitor is used to assess its role in inflammation and bone resorption in a murine model of lipopolysaccharide (LPS)-induced periodontal disease.

METHODS

Periodontal disease was induced in Balb/c mice by direct injections of LPS into the palatal gingival tissues adjacent to the maxillary first molars three times per week for 4 weeks. Animals were treated with biochemical inhibitor (2 mg/kg/daily) or the same volume of the vehicle by oral gavage. Microcomputed tomography analysis was used to assess bone resorption. Enzyme immunoassay determined LTB4, and enzyme-linked immunosorbent assays quantified tumor necrosis factor (TNF), interleukin (IL)-12, and IL-10 in gingival tissues. Histologic sections were used for the morphometric analysis (number of neutrophils and mononuclear cells). Osteoclasts were counted in tartrate-resistant acid phosphatase-stained sections.

RESULTS

Administration of 5-LO inhibitor effectively reduced production of LTB4 (23.7% decrease) and significantly reduced TNF and IL-12 levels in gingival tissues. Moreover, reduction of LTB4 levels in gingival tissues was associated with a significant decrease in bone resorption and a marked reduction in number of osteoclasts and inflammatory cells.

CONCLUSION

5-LO activity plays a relevant role in inflammation and bone resorption associated with the LPS model of experimental periodontal disease.

The role of 5-lipoxygenase in Aggregatibacter actinomycetemcomitans-induced alveolar bone loss

AIM

Leukotrienes (LTs) are pro-inflammatory lipid mediators formed by the enzyme 5-lipoxygenase (5-LO). The involvement of 5-LO metabolites in periodontal disease (PD) is not well defined. This study aimed to assess the role of 5-LO in experimental PD induced by Aggregatibacter actinomycetemcomitans (Aa).

MATERIAL AND METHODS

In vivo experiments were carried out using SV129 wild-type (WT) and 5-LO-deficient (5lo^-/- ) mice inoculated with Aa. Osteoclasts were stimulated in vitro with AaLPS in the presence or not of selective inhibitors of the 5-LO pathway, or LTB4 or platelet-activating factor (PAF), as PAF has already been shown to increase osteoclast activity.

RESULTS

In 5lo^-/- mice, there were no loss of alveolar bone and less TRAP-positive osteoclasts in periodontal tissues, after Aa inoculation, despite local production of TNF-α and IL-6. The differentiation and activity of osteoclasts stimulated with AaLPS were diminished in the presence of BLT1 antagonist or 5-LO inhibitor, but not in the presence of cysteinyl leukotriene receptor antagonist. The osteoclast differentiation induced by PAF was impaired by the BLT1 antagonism.

CONCLUSION

In conclusion, LTB4 but not CysLTs is important for Aa-induced alveolar bone loss. Overall, LTB4 affects osteoclast differentiation and activity and is a key intermediate of PAF-induced osteoclastogenesis.

Cerebral Ischemic Reperfusion Injury Following Recanalization of Large Vessel Occlusions

Although stroke has recently dropped to become the nation's fifth leading cause of mortality, it remains the top leading cause of morbidity and disability in the US. Recent advances in stroke treatment, including intravenous fibrinolysis and mechanical thromboembolectomy, allow treatment of a greater proportion of stroke patients than ever before. While intra-arterial fibrinolysis with recombinant tissue plasminogen is an effective for treatment of a broad range of acute ischemic strokes, endovascular mechanical thromboembolectomy procedures treat severe strokes due to large artery occlusions, often resistant to intravenous drug. Together, these procedures result in a greater proportion of revascularized stroke patients than ever before, up to 88% in 1 recent trial (EXTEND-IA). Subsequently, there is a growing need for neurointensivists to develop more effective strategies to manage stroke patients following successful reperfusion. Cerebral ischemic reperfusion injury (CIRI) is defined as deterioration of brain tissue suffered from ischemia that concomitantly reverses the benefits of re-establishing cerebral blood flow following mechanical or chemical therapies for acute ischemic stroke. Herein, we examine the pathophysiology of CIRI, imaging modalities, and potential neuroprotective strategies. Additionally, we sought to lay down a potential treatment approach for patients with CIRI following emergent endovascular recanalization for acute ischemic stroke.

Complement C5a Receptor is the Key Initiator of Neutrophil Adhesion Igniting Immune Complex-induced Arthritis

The deposition of immune complexes (IC) in tissues induces a "type III hypersensitivity" that results in tissue damage and underlies the pathogenesis of many autoimmune diseases. The neutrophil is the first immune cell recruited into sites of IC deposition and plays a critical role in shaping the overall tissue response. However, the mechanism by which IC initiate and propagate neutrophil infiltration into tissue is not known. Here, using intravital multiphoton joint imaging of IC-induced arthritis in live mice, we found that the complement C5a receptor (C5aR) was the key initiator of neutrophil adhesion on joint endothelium. C5a presented on joint endothelium induced β2 integrin-dependent neutrophil arrest, facilitating neutrophil spreading and transition to crawling, and subsequent leukotriene B₄ receptor (BLT1)-mediated extravasation of the first neutrophils. The chemokine receptor CCR1 promoted neutrophil crawling on the joint endothelium while CXCR2 amplified late neutrophil recruitment and survival once in the joint. Thus, imaging arthritis has defined a new paradigm for type III hypersensitivity where C5a directly initiates neutrophil adhesion on the joint endothelium igniting inflammation.

Cytochrome P450 and Lipoxygenase Metabolites on Renal Function

Arachidonic acid metabolites have a myriad of biological actions including effects on the kidney to alter renal hemodynamics and tubular transport processes. Cyclooxygenase metabolites are products of an arachidonic acid enzymatic pathway that has been extensively studied in regards to renal function. Two lesser-known enzymatic pathways of arachidonic acid metabolism are the lipoxygenase (LO) and cytochrome P450 (CYP) pathways. The importance of LO and CYP metabolites to renal hemodynamics and tubular transport processes is now being recognized. LO and CYP metabolites have actions to alter renal blood flow and glomerular filtration rate. Proximal and distal tubular sodium transport and fluid and electrolyte homeostasis are also significantly influenced by renal CYP and LO levels. Metabolites of the LO and CYP pathways also have renal actions that influence renal inflammation, proliferation, and apoptotic processes at vascular and epithelial cells. These renal LO and CYP pathway actions occur through generation of specific metabolites and cell-signaling mechanisms. Even though the renal physiological importance and actions for LO and CYP metabolites are readily apparent, major gaps remain in our understanding of these lipid mediators to renal function. Future studies will be needed to fill these major gaps regarding LO and CYP metabolites on renal function.

Matrikines are key regulators in modulating the amplitude of lung inflammation in acute pulmonary infection

Bioactive matrix fragments (matrikines) have been identified in a myriad of disorders, but their impact on the evolution of airway inflammation has not been demonstrated. We recently described a pathway where the matrikine and neutrophil chemoattractant proline–glycine–proline (PGP) could be degraded by the enzyme leukotriene A₄ hydrolase (LTA₄H). LTA₄H classically functions in the generation of pro-inflammatory leukotriene B₄, thus LTA₄H exhibits opposing pro- and anti-inflammatory activities. The physiological significance of this secondary anti-inflammatory activity remains unknown. Here we show, using readily resolving pulmonary inflammation models, that loss of this secondary activity leads to more pronounced and sustained inflammation and illness owing to PGP accumulation. PGP elicits an exacerbated neutrophilic inflammation and protease imbalance that further degrades the extracellular matrix, generating fragments that perpetuate inflammation. This highlights a critical role for the secondary anti-inflammatory activity of LTA₄H and thus has consequences for the generation of global LTA₄H inhibitors currently being developed.

Proteases degrade extracellular matrix during inflammation, releasing peptides that can recruit neutrophils. Here the authors show that degradation of such bioactive peptide by the enzyme leukotriene A4 hydrolase is critical to limit pulmonary inflammation during bacterial infection in mice.

The role of lipoxygenases in pathophysiology; new insights and future perspectives

Lipoxygenases (LOXs) are dioxygenases that catalyze the formation of corresponding hydroperoxides from polyunsaturated fatty acids such as linoleic acid and arachidonic acid. LOX enzymes are expressed in immune, epithelial, and tumor cells that display a variety of physiological functions, including inflammation, skin disorder, and tumorigenesis. In the humans and mice, six LOX isoforms have been known. 15-LOX, a prototypical enzyme originally found in reticulocytes shares the similarity of amino acid sequence as well as the biochemical property to plant LOX enzymes. 15-LOX-2, which is expressed in epithelial cells and leukocytes, has different substrate specificity in the humans and mice, therefore, the role of them in mammals has not been established. 12-LOX is an isoform expressed in epithelial cells and myeloid cells including platelets. Many mutations in this isoform are found in epithelial cancers, suggesting a potential link between 12-LOX and tumorigenesis. 12R-LOX can be found in the epithelial cells of the skin. Defects in this gene result in ichthyosis, a cutaneous disorder characterized by pathophysiologically dried skin due to abnormal loss of water from its epithelial cell layer. Similarly, eLOX-3, which is also expressed in the skin epithelial cells acting downstream 12R-LOX, is another causative factor for ichthyosis. 5-LOX is a distinct isoform playing an important role in asthma and inflammation. This isoform causes the constriction of bronchioles in response to cysteinyl leukotrienes such as LTC4, thus leading to asthma. It also induces neutrophilic inflammation by its recruitment in response to LTB4. Importantly, 5-LOX activity is strictly regulated by 5-LOX activating protein (FLAP) though the distribution of 5-LOX in the nucleus. Currently, pharmacological drugs targeting FLAP are actively developing. This review summarized these functions of LOX enzymes under pathophysiological conditions in mammals.

The role of leukotrienes in allergic diseases

Leukotrienes (LTs), both LTB4 and the cysteinyl LTs (CysLTs) LTC4, LTD4 and LTE4, are implicated in a wide variety of inflammatory disorders. These lipid mediators are generated from arachidonic acid via multistep enzymatic reactions through which arachidonic acid is liberated from membrane phospholipids through the action of phospholipase A2. LTB4 and CysLTs exert their biological effects by binding to cognate receptors, which belong to the G protein-coupled receptor superfamily. LTB4 is widely considered to be a potent chemoattractant for most subsets of leukocytes, whereas CysLTs are potent bronchoconstrictors that have effects on airway remodeling. LTs play a central role in the pathogenesis of asthma and many other inflammatory diseases. This review will provide an update on the synthesis, biological function, and relevance of LTs to the pathobiology of allergic diseases, and examine the current and future therapeutic prospects of LT modifiers.

Absence of ALOX5 gene prevents stress-induced memory deficits, synaptic dysfunction and tauopathy in a mouse model of Alzheimer's disease

Although the initial events of Alzheimer's disease (AD) are still not known, it is clear that the disease in its sporadic form results from the combination of genetic and environmental risk factors. Among the latter, behavioral stress has been increasingly recognized as an important factor in the propagation of AD. However, the mechanisms underlying this modulation remain to be fully investigated. Since stress up-regulates the ALOX5 gene product, 5-lipoxygenase (5LO), herein we investigated its role in modulating stress-dependent development of the AD phenotype. To reach this goal, triple transgenic (3xTg) mice and 3xTg genetically deficient for 5LO were investigated after undergoing a restraint/isolation paradigm. In the present paper, we found that 28 days of restraint/isolation stress worsened tau phosphorylation and solubility, increased glycogen synthase kinase 3β activity, compromised long-term potentiation and impaired fear-conditioned memory recall in 3xTg animals, but not in 3xTg animals lacking 5LO (3xTg/5LO-/-). These results highlight the novel functional role that the ALOX5 gene plays in the development of the biochemical, electrophysiological and behavioral sequelae of stress in the AD context. They provide critical support that this gene and its expressed protein are viable therapeutic targets to prevent the onset or delay the progression of AD in individuals exposed to this risk factor.

First report of interruption of mast cell degranulation and endothelial cells activation by anti-inflammatory drugs controlling the acute response provoked by Pseudoplatystoma fasciatum fish venom

This is the first report describing in mice the envenoming that possible to occur in humans provoked by Pseudoplatystomafasciatum and evaluated the different class of mediators involved in the inflammatory injury, identifying important targets for drugs intervention. First we demonstrate that P. fasciatum venom induces an acute inflammatory response characterized by the recruitment of immune cells into peripheral tissues choreographed by chemoattractants including lipid mediators (LTB4 and PGE2), cytokines (IL-1β and TNF-α), and chemokines (KC and MCP-1). Intravital microscopy studies showed that only high dose (60 μg) of venom promoted hemodynamic changes inducing an abundant number of thrombi of varying sizes in venules leading to transient venular stasis with reduced blood flow. We found that serotonin, leukotrine and prostaglandin are involved in edematogenic and nociceptive responses, since a selective COX-2 inhibitor, a non-specific inhibitor for cytokines and COX-2, and a non-selective 5-HT receptor antagonist were able to reduce both symptoms. In conclusion, our data show that the main symptoms of acute inflammation as pain provoked by P. fasciatum fish venom could be well managed by available drugs as COX-2 inhibitors as well dexamethasone or non-selective 5-HT receptor antagonists.

Gene knockout of 5-lipoxygenase rescues synaptic dysfunction and improves memory in the triple-transgenic model of Alzheimer's disease

5-Lipoxygenase (5LO) is upregulated in Alzheimer's disease (AD) and in vivo modulates the amyloidotic phenotype of amyloid precursor protein transgenic mice. However, no data are available on the effects that 5LO has on synaptic function, integrity and cognition. To address this issue, we used a genetic and a pharmacological approach by generating 3 × Tg mice deficient for 5LO and administering 3 × Tg mice with a 5LO inhibitor. Compared with controls, we found that even before the development of overt neuropathology, both animals manifested significant memory improvement, rescue of their synaptic dysfunction and amelioration of synaptic integrity. In addition, later in life, these mice had a significant reduction of Aβ and tau pathology. Our findings support a novel functional role for 5LO in regulating synaptic plasticity and memory. They establish this protein as a pleiotropic contributor to the development of the full spectrum of the AD phenotype, making it a valid therapeutic target for the treatment of AD.

Altered leukotriene B4 metabolism in CYP4F18-deficient mice does not impact inflammation following renal ischemia

Inflammatory responses to infection and injury must be restrained and negatively regulated to minimize damage to host tissue. One proposed mechanism involves enzymatic inactivation of the pro-inflammatory mediator leukotriene B4, but it is difficult to dissect the roles of various metabolic enzymes and pathways. A primary candidate for a regulatory pathway is omega oxidation of leukotriene B4 in neutrophils, presumptively by CYP4F3A in humans and CYP4F18 in mice. This pathway generates ω, ω-1, and ω-2 hydroxylated products of leukotriene B4, depending on species. We created mouse models targeting exons 8 and 9 of the Cyp4f18 allele that allows both conventional and conditional knockouts of Cyp4f18. Neutrophils from wild-type mice convert leukotriene B4 to 19-hydroxy leukotriene B4, and to a lesser extent 18-hydroxy leukotriene B4, whereas these products were not detected in neutrophils from conventional Cyp4f18 knockouts. A mouse model of renal ischemia-reperfusion injury was used to investigate the consequences of loss of CYP4F18 in vivo. There were no significant changes in infiltration of neutrophils and other leukocytes into kidney tissue as determined by flow cytometry and immunohistochemistry, or renal injury as assessed by histological scoring and measurement of blood urea nitrogen. It is concluded that CYP4F18 is necessary for omega oxidation of leukotriene B4 in neutrophils, and is not compensated by other CYP enzymes, but loss of this metabolic pathway is not sufficient to impact inflammation and injury following renal ischemia-reperfusion in mice.

The role of inflammation in colon cancer

Colorectal cancer (CRC) is the one of the leading causes of cancer-related deaths in the world. CRC is responsible for more than 600,000 deaths annually and incidence rates are increasing in most of the developing countries. Epidemiological and laboratory investigations suggest that environmental factors such as western style dietary habits, tobacco-smoking, and lack of physical activities are considered as risks for CRC. Molecular pathobiology of CRC implicates pro-inflammatory conditions to promote the tumor malignant progression, invasion, and metastasis. It is well known that patients with inflammatory bowel disease are at higher risk of CRC. Many evidences exist reiterating the link between Inflammation and CRC. Inflammation involves interaction between various immune cells, inflammatory cells, chemokines, cytokines, and pro-inflammatory mediators, such as cyclooxygenase (COX) and lipoxygenase (LOX) pathways, which may lead to signaling towards, tumor cell proliferation, growth, and invasion. Thus, this review will focus on mechanisms by which pro-inflammatory mediators and reactive oxygen/nitrogen species play a role in promoting CRC. Based on these mechanisms, various preventive strategies, involving anti-inflammatory agents, such as COX inhibitors, COX-LOX inhibitors, iNOS inhibitors, natural supplements/agents, and synthetic agents, that blocks the inflammatory pathways and suppress CRC are discussed in this review.

Effect of ascophyllan from brown algae Padina tetrastromatica on inflammation and oxidative stress in carrageenan-induced rats

Sulfated polysaccharide ascophyllan was isolated from the brown algae Padina tetrastromatica and purified by ion-exchange chromatography. Anti-inflammatory effect of ascophyllan fraction against carrageenan-induced paw edema in rats was studied. Paw edema in rats was induced by injecting 0.1 ml, 1 % carrageenan suspension in 0.9 % NaCl solution into the sub-plantar tissue of the right hind paw. Carrageenan caused a significant increase in the activity of inflammatory marker enzymes like lipoxygenases and cyclooxygenase in peripheral blood mononuclear cells and paw tissue and also increased the concentration of prostaglandin E2 (PGE2) and myeloperoxidase (MPO) in paw tissue. When compared to the reference drug diclofenac, ascophyllan fraction-3 (AF3) treatment significantly reduced the activities of anti-inflammatory enzymes, concentration of PGE2 and MPO. AF3 treatment decreased the mRNA level expression of TNF-α and IL-6. Concentration of thiobarbituric acid reactive substances was decreased. Activities of antioxidant enzymes and reduced glutathione level were increased on treatment with AF3. Histopathology of paw tissue showed decreased edema formation and cellular infiltration on supplementation with AF3. Thus the results demonstrated the potential beneficiary effect of ascophyllan fraction on carrageenan-treated rats.

Modulation of lipopolysaccharide-induced memory insult, γ-secretase, and neuroinflammation in triple transgenic mice by 5-lipoxygenase

Besides amyloid and tau pathology, a constant feature of Alzheimer's disease (AD) is an intense inflammatory response, which is considered an active player in its pathogenesis. The 5-Lipoxygenase (5LO) is a proinflammatory enzyme and an endogenous modulator of AD-like phenotype in mouse models of the disease. To further understand the role of 5LO in AD pathogenesis, we exposed the triple transgenic (3×Tg) and 3×Tg/5LO knockout mice to lipopolysaccharide (LPS), a known inducer of neuroinflammation, and evaluated its effect on their AD-like phenotype. 3×Tg mice treated with LPS manifested a worsening of behavior, γ-secretase up-regulation, and increased neuroinflammatory responses. These effects were completely prevented in 3×Tg mice genetically deficient for 5LO. By contrast, the absence of 5LO did not protect against increase in tau phosphorylation at specific epitopes that were mediated by the activation of the cyclin-dependent kinase 5. Our data demonstrate that the 5LO pathway affects key neuropathological features of the AD-like phenotype (behavior, abeta, microgliosis, astrocytosis) but not others (tau pathology) in the LPS-dependent neuroinflammation model. The opposite ways whereby 5LO influences the LPS-dependent effects in vivo supports the complex nature of the neuroinflammatory response in AD and its differential role in modulating amyloid and tau neuropathology.

Evaluation of Artemisia amygdalina D. for Anti-Inflammatory and Immunomodulatory Potential

Artemisia amygdalina D. is a critically endangered endemic medicinal plant of Kashmir Himalayas. In the current study anti-inflammatory and immunomodulatory activity of the plant was carried out. Carrageenan paw edema model was used to study the potential of the drug in inflammation in Wistar rats. SRBC-specific haemagglutination titre and DTH assays were carried out in Balb/C mice for observing the effect of test drugs on immune system. The plant extracts used as test drugs showed to have anti-inflammatory potential. The methanolic fraction was observed to have the maximum effect on the inhibition of paw edema formation with the inhibitory potential of 42.26%, while in the immunomodulation studies the test drugs were found to have the immunosuppressant activity with methanolic fraction again showing the maximum potential for the suppression of both humoral (55.89% and 47.91%) and cell-mediated immunity (62.27% and 57.21%). The plant in total seems to have the anti-inflammatory potential. The suppression of immune system suggests some mechanistic way by which the inhibition of inflammation takes place. Since, in chronic inflammation like arthritis, there is the involvement of immune system, the plant in that way may serve as an alternative for the treatment of such autoimmune diseases.

Knockout of 5-lipoxygenase prevents dexamethasone-induced tau pathology in 3xTg mice

Emerging evidence suggests that dysregulation stress hormones, such as glucocorticoids, in aged persons put them at a higher risk to develop Alzheimer's disease (AD). However, the mechanisms underlying such vulnerability remain to be unraveled. Pharmacologic inhibition of 5-lipoxygenase (5LO), an active player in AD pathogenesis whose protein level increases with aging in the human, has been shown to blunt glucocorticoid-mediated amyloid β (Ab) formation in vitro. In this article, we investigated the role of this pathway in modulating the development of the corticosteroid-dependent AD-like phenotype in the triple transgenic mice (3xTg). Dexamethasone was administered for 1 week to 3xTg or 3xTg genetically deficient for 5LO (3xTg/5LO-/-) mice, and its effect on memory, amyloid-β and tau levels, and metabolism assessed. At the end of the treatment, we observed that dexamethasone did not induce changes in behavior. Compared with controls, treated mice did not show significant alterations in brain soluble Aβ levels. While total tau protein levels were unmodified in all groups, we found that dexamethasone significantly increased tau phosphorylation at S396, as recognized by the antibody PHF-13, which was specifically associated with an increase in the GSK3β activity. Additionally, dexamethasone-treated mice had a significant increase in the tau insoluble fraction and reduction in the postsynaptic protein PDS-95. By contrast, these modifications were blunted in the 3xTg/5LO-/- mice. Our findings highlight the functional role that 5LO plays in stress-induced AD tau pathology and support the hypothesis that pharmacologic inhibition of this enzyme could be a useful tool for individuals with this risk factor.

5-Lipoxygenase facilitates healing after myocardial infarction

Early healing after myocardial infarction (MI) is characterized by a strong inflammatory reaction. Most leukotrienes are pro-inflammatory and are therefore potential mediators of healing and remodeling after myocardial ischemia. The enzyme 5-lipoxygenase (5-LOX) has a key role in the transformation of arachidonic acid in leukotrienes. Thus, we tested the effect of 5-LOX on healing after MI. After chronic coronary artery ligation, early mortality was significantly increased in 5-LOX^−/− when compared to matching wildtype (WT) mice due to left ventricular rupture. This effect could be reproduced in mice treated with the 5-LOX inhibitor Zileuton. A perfusion mismatch due to the vasoactive potential of leukotrienes is not responsible for left ventricular rupture since local blood flow assessed by magnetic resonance perfusion measurements was not different. However, after MI, there was an accentuation of the inflammatory reaction with an increase of pro-inflammatory macrophages. Yet, mortality was not changed in chimeric mice (WT vs. 5-LOX^−/− bone marrow in 5-LOX^−/− animals), indicating that an altered function of 5-LOX^−/− inflammatory cells is not responsible for the phenotype. Collagen production and accumulation of fibroblasts were significantly reduced in 5-LOX^−/− mice in vivo after MI. This might be due to an impaired migration of 5-LOX^−/− fibroblasts, as shown in vitro to serum. In conclusion, a lack or inhibition of 5-LOX increases mortality after MI because of healing defects. This is not mediated by a change in local blood flow, but through an altered inflammation and/or fibroblast function.

Anti-inflammatory effect of quinoline alkaloid skimmianine isolated from Ruta graveolens L

OBJECTIVE

The present study evaluates the anti-inflammatory effect of the quinoline alkaloid skimmianine (SKM), isolated from Ruta graveolens L., against carrageenan-induced acute inflammation.

METHODS

SKM at a dose of 5.0 mg/kg body weight was found to be the minimal concentration for maximal edema inhibition. Carrageenan suspension was administered into the sub-plantar tissue of the right hind paw 1 h after SKM and diclofenac (20 mg/kg) administration (i.p.). Paw edema was determined 3 h after carrageenan administration. The rats were then killed and mRNA expressions of TNF-α and IL-6, levels of PGE2 and TBARS, activities of COX-2, 5-LOX, SOD, catalase, glutathione peroxidase (GPx) and myeloperoxidase (MPO) and the level of nitrite were measured.

RESULTS

SKM treatment resulted in a decrease in the mRNA levels of TNF-α and IL-6, which are upstream events of the inflammatory cascade. The levels of PGE2 and NO and the activities of COX-2 and 5-LOX were also significantly reduced after SKM treatment. Neutrophil infiltration, lipid peroxidation and associated oxidative stress in the paw tissue were reduced following SKM treatment.

CONCLUSION

These results support the anti-inflammatory properties of skimmianine and its multi-targeted mechanism of action, suggesting its potential therapeutic efficacy in various inflammatory diseases.

Anti-inflammatory activity of lycopene isolated from Chlorella marina on type II collagen induced arthritis in Sprague Dawley rats

The role of commercially available lycopene (all-trans) from tomato in controlling arthritis has been reported. Even though many reports are available that the cis form of lycopene is more biologically active, no report seems to be available on lycopene (cis and trans) isolated from an easily available and culturable sources. In the present study, the anti-arthritic effect of lycopene (cis and trans) from the algae Chlorella marina (AL) has been compared with lycopene (all-trans) from tomato (TL) and indomethacin (Indo). Arthritis (CIA) was developed in male Sprague dawley rats by collagen and the following parameters were studied. The activities of inflammatory marker enzymes like cyclooxygenase (COX), lipoxygenase (LOX) and myeloperoxidase (MPO) were found to be decreased on treatment with AL when compared to TL and Indo. Changes in Erythrocyte sedimentation rate (ESR), white blood cell (WBC) count, red blood cells (RBC) count, hemoglobin (Hb), C-reactive protein (CRP), rheumatoid factor (RF), and ceruloplasmin levels observed in the blood of arthritic animals were brought back to normal by AL when compared to TL and Indo. Histopathology of paw and joint tissues showed marked reduction in edema on supplementation of AL. Thus these results indicate the potential beneficiary effect of algal lycopene on collagen induced arthritis in rats when compared to TL and even to the commonly used anti-inflammatory drug indomethacin. Therefore lycopene from C. marina would be recommended as a better natural source with increased activity and without side effects in the treatment of anti-inflammatory diseases.

Structure and ligand based drug design strategies in the development of novel 5- LOX inhibitors

Lipoxygenases (LOXs) are non-heme iron containing dioxygenases involved in the oxygenation of polyunsaturated fatty acids (PUFAs) such as arachidonic acid (AA). Depending on the position of insertion of oxygen, LOXs are classified into 5-, 8-, 9-, 12- and 15-LOX. Among these, 5-LOX is the most predominant isoform associated with the formation of 5-hydroperoxyeicosatetraenoic acid (5-HpETE), the precursor of non-peptido (LTB₄) and peptido (LTC₄, LTD₄, and LTE₄) leukotrienes. LTs are involved in inflammatory and allergic diseases like asthma, ulcerative colitis, rhinitis and also in cancer. Consequently 5-LOX has become target for the development of therapeutic molecules for treatment of various inflammatory disorders. Zileuton is one such inhibitor of 5-LOX approved for the treatment of asthma.

In the recent times, computer aided drug design (CADD) strategies have been applied successfully in drug development processes. A comprehensive review on structure based drug design strategies in the development of novel 5-LOX inhibitors is presented in this article. Since the crystal structure of 5-LOX has been recently solved, efforts to develop 5-LOX inhibitors have mostly relied on ligand based rational approaches. The present review provides a comprehensive survey on these strategies in the development of 5-LOX inhibitors.

The complement system in ischemia-reperfusion injuries

Tissue injury and inflammation following ischemia and reperfusion of various organs have been recognized for many years. Many reviews have been written over the last several decades outlining the role of complement in ischemia/reperfusion injury. This short review provides a current state of the art knowledge on the complement pathways activated, complement components involved and a review of the clinical biologics/inhibitors used in the clinical setting of ischemia/reperfusion. This is not a complete review of the complement system in ischemia and reperfusion injury but will give the reader an updated view point of the field, potential clinical use of complement inhibitors, and the future studies needed to advance the field.

Target Identification and Validation of (+)-2-(1-Hydroxyl-4-Oxocyclohexyl) Ethyl Caffeate, an Anti-Inflammatory Natural Product

(+)-2-(1-hydroxyl-4-oxocyclohexyl) ethyl caffeate (HOEC) was isolated from Incarvillea mairei var. granditlora (Wehrhahn) Grierson. The plants of the Incarvillea genus have long been used as folk medicines for the treatment of inflammation-related diseases in China. 5-Lipoxygenase (5-LOX), a key enzyme in the arachidonic acid (AA) cascade, was identified as a potential target of HOEC by a pulldown assay, and then extensively validated by biosensor-based affinity detection, enzyme-based activity assays, cell-based AA metabolite analysis and computer-aided AA network simulation. Further in vivo studies of AA-induced ear oedema, ovalbumin (OVA)-induced lung inflammation and collagen-induced arthritis demonstrated the anti-inflammatory potency and validated the therapeutic target of HOEC. This work revealed that HOEC acted as an anti-inflammatory agent targeting 5-LOX, which not only confirmed the key role of 5-LOX in inflammation but also provided a paradigm for the exploration of natural product mechanisms of action.

Anti-inflammatory activity of methyl palmitate and ethyl palmitate in different experimental rat models

Methyl palmitate (MP) and ethyl palmitate (EP) are naturally occurring fatty acid esters reported as inflammatory cell inhibitors. In the current study, the potential anti-inflammatory activity of MP and EP was evaluated in different experimental rat models. Results showed that MP and EP caused reduction of carrageenan-induced rat paw edema in addition to diminishing prostaglandin E2 (PGE2) level in the inflammatory exudates. In lipopolysaccharide (LPS)-induced endotoxemia in rats, MP and EP reduced plasma levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). MP and EP decreased NF-κB expression in liver and lung tissues and ameliorated histopathological changes caused by LPS. Topical application of MP and EP reduced ear edema induced by croton oil in rats. In the same animal model, MP and EP reduced neutrophil infiltration, as indicated by decreased myeloperoxidase (MPO) activity. In conclusion, this study demonstrates the effectiveness of MP and EP in combating inflammation in several experimental models.

Role of lipoxins, resolvins, and other bioactive lipids in colon and pancreatic cancer

Unresolved inflammation, due to insufficient production of proresolving anti-inflammatory lipid mediators, can lead to an increased risk of tumorigenesis and tumor cell invasiveness. Various bioactive lipids, particularly those formed by cyclooxygenase (COX) and lipoxygenase (LOX) enzymes, have been well established as therapeutic targets for many epithelial cancers. Emerging studies suggest that there is a role for anti-inflammatory bioactive lipids and their mediators during the resolution phase of inflammation. These proresolving bioactive lipids, including lipoxins (LXs) and resolvins (RVs), have potent anti-inflammatory and anti-carcinogenic properties. The molecular signaling pathways controlling generation and degradation of the proresolving mediators LXs and RVs are now being elucidated, and the component molecules may serve as new targets for regulation of inflammation and inflammation-associated cancers like colon and pancreatic cancers. This review will highlight the recent advances in our understanding of how these bioactive lipids and proresolving mediators may function with various immune cells and cytokines in inhibiting tumor cell proliferation and progression and invasiveness of colon and pancreatic cancers.

2-(4-(Biphenyl-4-ylamino)-6-chloropyrimidin-2-ylthio)octanoic acid (HZ52)--a novel type of 5-lipoxygenase inhibitor with favourable molecular pharmacology and efficacy in vivo

BACKGROUND AND PURPOSE

5-Lipoxygenase (5-LO) is the key enzyme in the biosynthesis of pro-inflammatory leukotrienes (LTs) representing a potential target for pharmacological intervention with inflammation and allergic disorders. Although many LT synthesis inhibitors are effective in simple in vitro test systems, they frequently fail in vivo due to lack of efficacy. Here, we attempted to assess the pharmacological potential of the previously identified 5-LO inhibitor 2-(4-(biphenyl-4-ylamino)-6-chloropyrimidin-2-ylthio)octanoic acid (HZ52).

EXPERIMENTAL APPROACH

We evaluated the efficacy of HZ52 in vivo using carrageenan-induced pleurisy in rats and platelet-activating factor (PAF)-induced lethal shock in mice. We also characterized 5-LO inhibition by HZ52 at the cellular and molecular level in comparison with other types of 5-LO inhibitor, that is, BWA4C, ZM230487 and hyperforin.

KEY RESULTS

HZ52, 1.5 mg·kg⁻¹ i.p., prevented carrageenan-induced pleurisy accompanied by reduced LTB(4) levels and protected mice (10 mg·kg⁻¹, i.p.) against PAF-induced shock. Detailed analysis in cell-based and cell-free assays revealed that inhibition of 5-LO by HZ52 (i) does not depend on radical scavenging properties and is reversible; (ii) is not impaired by an increased peroxide tone or by elevated substrate concentrations; and (iii) is little affected by the cell stimulus or by phospholipids, glycerides, membranes or Ca²⁺.

CONCLUSIONS AND IMPLICATIONS

HZ52 is a promising new type of 5-LO inhibitor with efficacy in vivo and with a favourable pharmacological profile. It possesses a unique 5-LO inhibitory mechanism different from classical 5-LO inhibitors and seemingly lacks the typical disadvantages of former classes of LT synthesis blockers.

ONZIN deficiency attenuates contact hypersensitivity responses in mice

ONZIN is abundantly expressed in immune cells of both the myeloid and lymphoid lineage. Expression by lymphoid cells has been reported to further increase after cutaneous exposure of mice to antigens and haptens capable of inducing contact hypersensitivity (CHS), suggesting that ONZIN has a critical role in this response. Here, we report that indeed ONZIN-deficient mice develop attenuated CHS to a number of different haptens. Dampened CHS responses correlated with a significant reduction in pro-inflammatory IL-6 at the challenge site in ONZIN-deficient animals, compared with wild-type controls. Together the study of these animals indicates that loss of ONZIN impacts the effector phase of the CHS response through the regulation of pro-inflammatory factors.

Role of neutrophils in acrylonitrile-induced gastric mucosal damage

Acrylonitrile (ACN) is a widely used intermediate in the manufacture of plastics, acrylic fibers, synthetic rubbers and resins that are used in a variety of products including food containers and medical devices. ACN is a possible human carcinogen and a documented animal carcinogen, with the stomach being an important target of its toxicity. ACN has been previously reported to require metabolic activation to reactive intermediates and finally to cyanide (CN⁻). The current study aimed at exploring the potential role of neutrophils in ACN-induced gastric damage in rats. Experimental neutropenia was attained by injecting rats with methotrexate. This significantly ameliorated gastric mucosal injury induced by ACN. This is evidenced by protection against the increase in gastric ulcer index, myeloperoxidase (MPO) activity and CN⁻ level. Also, neutropenia guarded against the decrease in prostaglandin E2 (PGE2), induction of oxidative stress and reduction of total nitrites and alleviated histopathological alterations in rat stomachs. These data indicate that neutrophil infiltration is, at least partly, involved in ACN-induced gastric damage in rats.

Anti-inflammatory effects of the chloroform extract of Pulicaria guestii ameliorated the neutrophil infiltration and nitric oxide generation in rats

Pulicaria guestii Rech.f. & Rawi is a fragrant, perennial herb, which grows wild, west of Al-Madinah, Saudi Arabia. Several reports were published on the anti-inflammatory activity of the sesquiterpene lactones, phenolics and flavonoids, which constitute the main active constituents of the members of the genus Pulicaria. The present study was designed to explore the potential anti-inflammatory effect of P. guestii in several experimental models. The methanol extract of the dried aerial parts of P. guestii was extracted with petroleum ether, chloroform and n-butanol. The chloroform extract was analysed on TLC and examined under UV and visible light in presence of AlCl(3) spray. The free radical scavenging activity and the total phenolic content in the CHCl(3) extract were estimated. The crude methanol extract and the CHCl(3) fraction were examined against carrageenin-induced paw edema and ear edema induced by croton oil application. The crude methanolic extract significantly reduced carrageenin-induced rat paw edema. After fractionation, the chloroform fraction caused significant reduction in carrageenin-induced rat paw edema in addition to diminishing prostaglandin E(2) (PGE(2)) in the inflammatory exudates. Topical application of chloroform fraction significantly reduced rat ear edema induced by croton oil application. In the same model, chloroform fraction reduced neutrophil infiltration, as indicated by the significant decrease in myeloperoxidase activity, and ameliorated histopathological changes induced by croton oil application. In lipopolysaccharide-induced inflammation in rat air pouch, chloroform fraction significantly reduced the nitric oxide level and tumor necrosis factor-α release. In conclusion, the chloroform fraction of P. guestii extract possesses anti-inflammatory activity in several experimental models. Further investigations are needed to identify the active constituents responsible for this anti-inflammatory activity.

Molecular targets of phytochemicals for cancer prevention

Although successful for a limited number of tumour types, the efficacy of cancer therapies, especially for late-stage disease, remains poor overall. Many have argued that this could be avoided by focusing on cancer prevention, which has now entered the arena of targeted therapies. During the process of identifying preventive agents, dietary phytochemicals, which are thought to be safe for human use, have emerged as modulators of key cellular signalling pathways. The task now is to understand how these chemicals perturb these pathways by modelling their interactions with their target proteins.

Role of TNFR-related 2 mediated immune responses in dextran sulfate sodium-induced inflammatory bowel disease

Previous work has suggested that the LIGHT-TR2 costimulatory pathway plays a role in the acute and chronic stages of dextran sulfate sodium (DSS)-induced colitis [Steinberg et al. (2008); Wang et al. (2005)]. To clarify the role of TNFR-related 2 (TR2) signaling in the maintenance of intestinal homeostasis, we generated a TR2 knock-out (KO) mouse. Using DSS to induce colitis, we compared the colitic symptoms and pathological changes in wild type (WT) and TR2 KO mice, and the production of cytokines by the diseased colons. We also studied the role of TR2 in suppressing innate and adaptive immunity in the DSS model. TR2 deficient mice were characterized by reduced symptoms of intestinal inflammation compared with wild-type mice, and reduced production of cytokines. We therefore generated a monoclonal antibody against mouse TR2 which was specific to TR2 and capable of blocking TR2 signals. With this antibody, we demonstrated that antagonizing TR2 during the development of DSS-induced colitis reduced the symptoms of inflammation. Our findings suggest that TR2 is an important mediator in colitis, and may serve as a therapeutic target in inflammatory bowel disease.

Joint tissues amplify inflammation and alter their invasive behavior via leukotriene B4 in experimental inflammatory arthritis

Mechanisms by which mesenchymal-derived tissue lineages participate in amplifying and perpetuating synovial inflammation in arthritis have been relatively underinvestigated and are therefore poorly understood. Elucidating these processes is likely to provide new insights into the pathogenesis of multiple diseases. Leukotriene B(4) (LTB(4)) is a potent proinflammatory lipid mediator that initiates and amplifies synovial inflammation in the K/BxN model of arthritis. We sought to elucidate mechanisms by which mesenchymal-derived fibroblast-like synoviocytes (FLSs) perpetuate synovial inflammation. We focused on the abilities of FLSs to contribute to LTB(4) synthesis and to respond to LTB(4) within the joint. Using a series of bone marrow chimeras generated from 5-lipoxygenase(-/-) and leukotriene A(4) (LTA(4)) hydrolase(-/-) mice, we demonstrate that FLSs generate sufficient levels of LTB(4) production through transcellular metabolism in K/BxN serum-induced arthritis to drive inflammatory arthritis. FLSs-which comprise the predominant lineage populating the synovial lining-are competent to metabolize exogenous LTA(4) into LTB(4) ex vivo. Stimulation of FLSs with TNF increased their capacity to generate LTB(4) 3-fold without inducing the expression of LTA(4) hydrolase protein. Moreover, LTB(4) (acting via LTB(4) receptor 1) was found to modulate the migratory and invasive activity of FLSs in vitro and also promote joint erosion by pannus tissue in vivo. Our results identify novel roles for FLSs and LTB(4) in joints, placing LTB(4) regulation of FLS biology at the center of a previously unrecognized amplification loop for synovial inflammation and tissue pathology.

Redox control in mammalian embryo development

The development of an embryo constitutes a complex choreography of regulatory events that underlies precise temporal and spatial control. Throughout this process the embryo encounters ever changing environments, which challenge its metabolism. Oxygen is required for embryogenesis but it also poses a potential hazard via formation of reactive oxygen and reactive nitrogen species (ROS/RNS). These metabolites are capable of modifying macromolecules (lipids, proteins, nucleic acids) and altering their biological functions. On one hand, such modifications may have deleterious consequences and must be counteracted by antioxidant defense systems. On the other hand, ROS/RNS function as essential signal transducers regulating the cellular phenotype. In this context the combined maternal/embryonic redox homeostasis is of major importance and dysregulations in the equilibrium of pro- and antioxidative processes retard embryo development, leading to organ malformation and embryo lethality. Silencing the in vivo expression of pro- and antioxidative enzymes provided deeper insights into the role of the embryonic redox equilibrium. Moreover, novel mechanisms linking the cellular redox homeostasis to gene expression regulation have recently been discovered (oxygen sensing DNA demethylases and protein phosphatases, redox-sensitive microRNAs and transcription factors, moonlighting enzymes of the cellular redox homeostasis) and their contribution to embryo development is critically reviewed.

Significance of COX-2, PPARγ and NF-κB p65 expression in ulcerative colitis

AIM: To investigate the significance of cyclooxygenase-2 COX-2), peroxisome proliferator-activated receptor γ (PPARγ), and nuclear transcription factor-kappa B (NF-κB) p65 expression in ulcerative colitis (UC) and to analyze their correlation.

METHODS: The colonic biopsies were collected from 32 UC patients and 26 healthy controls at West China Hospital. The endoscopic grades of UC were assessed according to the Baron Scale. The pathological grades of UC were classified according to the Riley-Mani-Goodman classification. The expression of COX-2, PPARγ and NF-κB P65 proteins in colonic mucosa was determined by immunohistochemistry.

RESULTS: According to Riley-Mani-Goodman classification, 19 UC patients had grade I disease, 9 had grade II disease, and 4 had grade III disease. COX-2 and NF-κB p65 proteins were mainly distributed in epithelial cells and lamina propria inflammatory cells in UC, but were negatively or weakly expressed in normal colonic mucosa. The expression levels of COX-2 and NF-κB p65 proteins in UC patients were significantly higher than those in healthy controls (both P < 0.05). PPARγ was mainly expressed in the cytoplasm of colonic epithelial cells. The expression of PPARγ protein in UC patients was significantly lower than that in healthy controls (P < 0.05). Although the expression of COX-2 protein was not correlated with the histological grade of UC, a good correlation between the expression of PPARγ and NF-κB p65 and histological grade was noted (H = 411, P < 0.05; H = 16.77, P < 0.01). There is a positive correlation between COX-2 and NF-κB p65 protein expression in UC (r = 0.92, P < 0.01), while a negative correlation was found between NF-κB P65 and PPARγ protein expression (r = 0.905, P < 0.01).

CONCLUSION: NF-κB expression is involved in the development and progression of UC. COX-2 and PPARγ are also involved in the process of inflammation/injury in UC. COX-2 affects the process of inflammation in UC possibly by acting upon the PPARγ-NF-κB p65 signaling pathway. COX-2, PPARγ and NF-κB p65 may be used as targets for UC therapy.