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LE Magazine October 2003

Licofelone (ML-3000), a dual inhibitor of 5-lipoxygenase and cyclooxygenase, reduces the level of cartilage chondrocyte death in vivo in experimental dog osteoarthritis: inhibition of pro-apoptotic factors.
OBJECTIVE: To evaluate in vivo therapeutic efficacy of licofelone, a novel competitive dual inhibitor of 5-lipoxygenase (5-LOX) and cyclooxygenase (COX) in chondrocyte death in the canine ligament transection model of osteoarthritis (OA), and to explore its effect on factors involved in the apoptotic phenomenon, i.e., caspase-3, COX-2 and inducible nitric oxide synthase (iNOS). METHODS: Cartilage specimens were obtained from three experimental groups of dogs: Group 1, dogs subjected to sectioning of the anterior cruciate ligament of the right knee and given placebo treatment; Groups 2 and 3, operated dogs that received oral treatment with licofelone (2.5 or 5.0 mg/kg/day, respectively) for eight weeks starting immediately after surgery. All dogs were killed eight weeks postsurgery. The cartilage level of chondrocyte death was detected by TUNEL reaction. Cartilage distribution of caspase-3, COX-2 and iNOS was documented by immunohistochemistry using specific antibodies, and other levels were quantified by morphometric analysis. RESULTS: In cartilage specimens from placebo treated dogs a large number of chondrocytes in the superficial layers stained positive for TUNEL reaction. Treatment with therapeutic concentrations of licofelone (2.5 and 5.0 mg/kg/day) markedly reduced the level of chondrocyte apoptosis to the same extent in both therapeutic groups (p < 0.0001, p < 0.002, respectively). In these groups, the levels of caspase-3, COX-2 and iNOS in cartilage from both condyles and plateaus were also significantly decreased (p < 0.0001, p < 0.0001, p < 0.0002, respectively) compared to the control (placebo) group. CONCLUSION: Licofelone is an effective treatment in vivo, capable of reducing the level of OA chondrocyte death. This effect is likely mediated by a decrease in the level of caspase-3 activity, which may be related to the reduced production of two major factors involved in chondrocyte apoptosis, NO and prostaglandin E2. These findings may explain some of the mechanisms by which licofelone reduces the progression of experimental OA.

J Rheumatol. 2002 Jul;29(7):1446-53.

Differential regulation of prostaglandin E2 and thromboxane A2 production in human monocytes: implications for the use of cyclooxygenase inhibitors.
There is an autocrine relationship between eicosanoid and cytokine synthesis, with the ratio of prostaglandin E2 (PGE2)/thromboxane A2 (TXA2) being one of the determinants of the level of cytokine synthesis. In monocytes, cyclooxygenase type 1 (COX-1) activity appears to favor TXA2 production and COX-2 activity appears to favor PGE2 production. This has led to speculation regarding possible linkage of COX isozymes with PGE and TXA synthase. We have studied the kinetics of PGE2 and TXA2 synthesis under conditions that rely on COX-1 or -2 activity. With small amounts of endogenously generated prostaglandin H2 (PGH2), TXA2 synthesis was greater than PGE2. With greater amounts of endogenously generated PGH2, PGE2 synthesis was greater than TXA2. Also, TXA synthase was saturated at lower substrate concentrations than PGE synthase. This pattern was observed irrespective of whether PGH2 was produced by COX-1 or COX-2 or whether it was added directly. Furthermore, the inhibition of eicosanoid production by the action of nonsteroidal anti-inflammatory drugs or by the prevention of COX-2 induction with the p38 mitogen-activated protein kinase inhibitor SKF86002 was greater for PGE2 than for TXA2. It is proposed that different kinetics of PGE synthase and TXA synthase account for the patterns of production of these eicosanoids in monocytes under a variety of experimental conditions. These properties provide an alternative explanation to notional linkage or compartmentalization of COX-1 or -2 with the respective terminal synthases and that therapeutically induced changes in eicosanoid ratios toward predominance of TXA2 may have unwanted effects in long-term anti-inflammatory and anti-arthritic therapy.

J Immunol. 2000 Aug 1;165(3):1605-11

Thromboxane A2 induces leukotriene B4 synthesis that in turn mediates neutrophil diapedesis via CD 18 activation.
Previous studies have indicated that thromboxane (Tx) and leukotriene (LT) B4 act synergistically to induce neutrophil (PMN) adhesion in the microvasculature. This study explores the ability of Tx to induce LTB4 synthesis, which then leads to activation of PMN and endothelial adhesion receptors. Tx-mimic (U46619, 1 microgram/ml) was administered into abraded skin chambers placed on the backs of rabbits (n = 6). After three hours LTB4 was synthesized in the blister fluid at 385 pg/ml, a value higher than levels in saline-treated blisters, 10 pg/ml (P less than 0.05). The LTB4 generation following Tx-mimic was correlated (P less than 0.05, r = 0.70) with neutrophil diapedesis. These averaged 645 PMN/mm3, values higher than saline values of 20 PMN/mm3 (P less than 0.05). Intravenous (iv) treatment of other rabbits (n = 4) with the lipoxygenase inhibitor diethylcarbamazine at 60 mg/kg, followed by 40 mg/kg/hr, prevented Tx-mimic-induced LTB4 synthesis (10 pg/ml) and diapedesis (19 PMN/mm3) (both P less than 0.05). Intravenous treatment of yet other rabbits (n = 4) with the anti-CD 18 monoclonal antibody R 15.7 at 1 mg/kg abolished Tx-induced diapedesis (3 PMN/mm3) (P less than 0.05). In contrast, local administration of 3 ng of the protein synthesis inhibitor actinomycin D, to prevent expression of endothelial adhesion proteins, limited TNF- but not Tx-induced diapedesis. The data indicate that Tx-induced diapedesis is mediated by the generation of LTB4 and the activation of neutrophil CD 18 but not endothelial adhesion proteins.

Microvasc Res. 1991 May;41(3):367-75

Anti-cytokine therapy in chronic destructive arthritis.
Tumor necrosis factor (TNF) and interleukin-1 (IL-1) are considered to be master cytokines in chronic, destructive arthritis. Therapeutic approaches in rheumatoid arthritis (RA) patients have so far focused mainly on TNF, which is a major inflammatory mediator in RA and a potent inducer of IL-1; anti-TNF therapy shows great efficacy in RA patients. However, it is not effective in all patients, nor does it fully control the arthritic process in affected joints of good responders. Directed therapy for IL-1, with IL-1 receptor antagonist, mainly reduces erosions and is marginally anti-inflammatory. It is as yet unclear whether the limited effect is akin to the RA process or linked to suboptimal blocking of IL-1. Analysis of cytokine patterns in early synovial biopsies of RA patients reveals a marked heterogeneity, with variable staining of TNF and IL-1 beta, indicative of TNF-independent IL-1 production in at least some patients. Evidence for this pathway emerged from experimental arthritises in rodents, and is summarized in this review. If elements of the models apply to the arthritic process in RA patients, it is necessary to block IL-1 beta in addition to TNF.

Arthritis Res. 2001;3(1):18-26. Epub 2000 Nov 10

Ex-vivo in-vitro inhibition of lipopolysaccharide stimulated tumor necrosis factor-alpha and interleukin-1 beta secretion in human whole blood by extractum urticae dioicae foliorum.
An extract of Urtica dioica folium (IDS 23, Rheuma-Hek), monographed positively for adjuvant therapy of rheumatic diseases and with known effects in partial inhibition of prostaglandin and leukotriene synthesis in vitro, was investigated with respect to effects of the extract on the lipopolysaccharide (LPS) stimulated secretion of proinflammatory cytokines in human whole blood of healthy volunteers. In the assay system used, LPS stimulated human whole blood showed a straight increase of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) secretion reaching maximum concentrations within 24 hours following a plateau and slight decrease up to 65 hours, respectively. The concentrations of these cytokines was strongly positively correlated with the number of monocytes/macrophages of each volunteer. TNF-alpha and IL-1 beta concentration after LPS stimulation was significantly reduced by simultaneously given IDS 23 in a strictly dose dependent manner. At time 24 hours these cytokine concentrations were reduced by 50.8% and 99.7%, respectively, using the highest test IDS 23 assay concentration of 5 mg/ml (p < 0.001). After 65 hours the corresponding inhibition was 38.9% and 99.9%, respectively (p < 0.001). On the other hand IDS 23 showed no inhibition but stimulated IL-6 secretion in absence of LPS alone. Simultaneously given LPS and IDS 23 resulted in no further increase. In contrast to described effects on arachidonic acid cascade in vitro, tested Urtica dioica phenol carbon acid derivates and flavonoids such as caffeic malic acid, caffeic acid, chlorogenic acid, quercetin and rutin did not influence LPS stimulated TNF-alpha, IL-1 beta and IL-6 secretion in tested concentrations up to 5 x 10(-5) mol/l. These further findings on the pharmacological mechanism of action of Urticae dioica folia may explain the positive effects of this extract in the treatment of rheumatic diseases.

Arzneimittelforschung. 1996 Apr;46(4):389-94

Plant extracts from stinging nettle (Urtica dioica), an antirheumatic remedy, inhibit the proinflammatory transcription factor NF-kappaB.
Activation of transcription factor NF-kappaB is elevated in several chronic inflammatory diseases and is responsible for the enhanced expression of many proinflammatory gene products. Extracts from leaves of stinging nettle (Urtica dioica) are used as antiinflammatory remedies in rheumatoid arthritis. Standardized preparations of these extracts (IDS23) suppress cytokine production, but their mode of action remains unclear. Here we demonstrate that treatment of different cells with IDS23 potently inhibits NF-kappaB activation. An inhibitory effect was observed in response to several stimuli, suggesting that IDS23 suppressed a common NF-kappaB pathway. Inhibition of NF-kappaB activation by IDS23 was not mediated by a direct modification of DNA binding, but rather by preventing degradation of its inhibitory subunit IkappaB-alpha. Our results suggests that part of the antiinflammatory effect of Urtica extract may be ascribed to its inhibitory effect on NF-kappaB activation.

FEBS Lett. 1999 Jan 8;442(1):89-94

Effects of the antirheumatic remedy Hox alpha-a new stinging nettle leaf extract-on matrix metalloproteinases in human chondrocytes in vitro.
Inflammatory joint diseases are characterized by enhanced extracellular matrix degradation which is predominantly mediated by cytokine-stimulated upregulation of matrix metalloproteinase (MMP) expression. Besides tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) produced by articular chondrocytes and synovial macrophages, is the most important cytokine stimulating MMP expression under inflammatory conditions. Blockade of these two cytokines and their downstream effectors are suitable molecular targets of antirheumatic therapy. Hox alpha is a novel stinging nettle (Urtica dioica/Urtica urens) leaf extract used for treatment of rheumatic diseases. The aim of the present study was to clarify the effects of Hox alpha and the monosubstance 13-HOTrE (13-Hydroxyoctadecatrienic acid) on the expression of matrix metalloproteinase-1, -3 and -9 proteins (MMP-1, -3, -9). Human chondrocytes were cultured on collagen type-II-coated petri dishes, exposed to IL-1beta and treated with or without Hox alpha and 13-HOTrE. A close analysis by immunofluorescence microscopy and western blot analysis showed that Hox alpha and 13-HOTrE significantly suppressed IL-1beta-induced expression of matrix metalloproteinase-1, -3 and -9 proteins on the chondrocytes in vitro. The potential of Hox alpha and 13-HOTrE to suppress the expression of matrix metalloproteinases may explain the clinical efficacy of stinging nettle leaf extracts in treatment of rheumatoid arthritis. These results suggest that the monosubstance 13-HOTrE is one of the more active antiinflammatory substances in Hox alpha and that Hox alpha may be a promising remedy for therapy of inflammatory joint diseases.

Histol Histopathol. 2002 Apr;17(2):477-85

Oral aspirin and ibuprofen increase cytokine-induced synthesis of IL-1 beta and of tumour necrosis factor-alpha ex vivo.
We investigated the effect of oral aspirin and ibuprofen on the ex vivo synthesis of interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-2, IL-6, tumor necrosis factor-alpha (TNF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) by stimulated peripheral blood mononuclear cells (PBMC) from healthy volunteers. Seven volunteers took 325 mg of aspirin daily for 14 days. Three weeks after ending aspirin medication, ex vivo IL-1 beta and TNF synthesis induced by exogenous IL-1 alpha was elevated threefold compared to the pre-aspirin value (P = 0.01 and P = 0.005, respectively). Using lipopolysaccharide (LPS) as a stimulus, no influence of oral aspirin was observed. The increase in cytokine synthesis did not parallel decreased synthesis of prostaglandin E2 (PGE2). Seven weeks after discontinuation of aspirin, cytokine and PGE-2 production returned to pre-aspirin levels. Another seven volunteers took 200 mg of ibuprofen daily for 12 days. Again, there was no effect on LPS- or Staphylococcus epidermidis-induced cytokine synthesis. However, IL-1 alpha-induced synthesis of IL-1 beta was elevated to a mean individual increase of 538% (P < 0.001) and synthesis of TNF was elevated to 270% (P < 0.001) at the end of ibuprofen medication and two weeks after discontinuation of ibuprofen. There were parallel increases in PGE2 and both returned to their pre-ibuprofen levels five weeks after stopping. Although inhibitors of cyclo-oxygenase blunt PGE2-mediated symptoms such as fever and pain, we conclude that short term use of either aspirin or ibuprofen results in a 'rebound' increase in cytokine-induced cytokine synthesis that is not observed in LPS-induced cytokines.

Immunology. 1996 Feb;87(2):264-70

Mechanism of 5-lipoxygenase inhibition by acetyl-11-keto-beta-boswellic acid.
The formation of 5-lipoxygenase (EC products from endogenous substrate by intact rat neutrophilic granulocytes and from exogenous arachidonic acid by rat granulocyte 105,000 x g supernatants and affinity chromatography-purified human leukocyte 5-lipoxygenase was inhibited by acetyl-11-keto-beta-boswellic acid (IC50 values of 1.5 microM, 8 microM, and 16 microM respectively). With other pentacyclic triterpenes lacking the 11-keto function and/or the carboxyl function on ring A (e.g., amyrin and ursolic acid), no 5-lipoxygenase inhibition was observed. The presence of the noninhibitory pentacyclic triterpenes both in intact cells and in the cell-free system caused a concentration-dependent reversal of the 5-lipoxygenase inhibition by acetyl-11-keto-beta-boswellic acid, whereas the inhibitory actions of 5-lipoxygenase inhibitors from different chemical classes (MK-886, L-739,010, ZM-230,487 and nordihydroguaiaretic acid) were not modified. The inhibition by acetyl-11-keto-beta-boswellic acid and the antagonism by noninhibitory pentacyclic triterpenes were not due to nonspecific lipophilic interactions, because lipophilic four-ring compounds (cholesterol, cortisone and testosterone) neither inhibited the activity of the 5-lipoxygenase nor antagonized the inhibitory action of acetyl-11-keto-beta-boswellic acid. Therefore, we conclude that acetyl-11-keto-beta-boswellic acid acts directly on the 5-lipoxygenase enzyme at a selective site for pentacyclic triterpenes that is different from the arachidonate substrate binding site.

Mol Pharmacol. 1995 Jun;47(6):1212-6

Inhibition of prostaglandin and leukotriene biosynthesis by gingerols and diarylheptanoids.
The rhizomes of Zingiber officinale (ginger) and Alpinia officinarum contain potent inhibitors against prostaglandin biosynthesizing enzyme (PG synthetase). Gingerols and diarylhepatanoids were identified as active compounds. Their possible mechanism of action which was deduced from the structures of active compounds indicated that the inhibitors would also be active against arachidonate 5-lipoxygenase, an enzyme of leukotriene (LT) biosynthesis. This was verified by testing their inhibitory effects on 5-lipoxygenase prepared from RBL-1 cells. A diarylheptanoid with catechol group was the most active compound against 5-lipoxygenase, while yakuchinone A was the most active against PG synthetase.

Chem Pharm Bull (Tokyo). 1992 Feb;40(2):387-91.

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