A. M. Silván

Effects of six diterpenes on macrophage eicosanoid biosynthesis.

Six diterpenes (three clerodanes, two abietanes and one rosane) were tested for interactions with the cyclooxygenase and 5-lipoxygenase pathways of arachidonate metabolism and for effects of nitric oxide production. Two abietane diterpenes, aethiopinone and 11,12-dihydroxy-6-oxo-8,11,13-abietatriene and the rosane lagascatriol showed a remarkable effect on COX-1 pathway of PGE2 release in calcium ionophore A23187-stimulated peritoneal macrophages. Only the two latter diterpenes showed inhibition on COX-2 pathway of PGE2 release in E. coli LPS-stimulated peritoneal macrophages. In addition, all compounds assayed were inhibitors of LTC4 release with IC50 < or = 10 microM. Clerodane diterpenes were inactive in COX assay. None of the diterpenes assayed, except 11,12-dihydroxy-6-oxo-8,11,13-abietatriene, affected NO production. The results obtained suggest that the cellular mechanisms of action of some of these substances may involve inhibition of cyclooxygenase/lipoxygenase pathways and nitric oxide production.

Effects of furocoumarins from Cachrys trifida on some macrophage functions.

Phytochemical and biological studies aimed at the discovery and development of novel antiinflammatory agents from natural sources have been conducted in our laboratory for a number of years. In this communication, three naturally occurring furocoumarins (imperatorin, isoimperatorin and prantschimgin) were evaluated as potential inhibitors of some macrophage functions involved in the inflammatory process. These furocoumarins have been tested in two experimental systems: ionophore‐stimulated mouse peritoneal macrophages serve as a source of cyclooxygenase‐1 and 5‐lipoxygenase, and mouse peritoneal macrophages stimulated with E. coli lipopolysaccharide are the means of testing for anti‐cyclooxygenase‐2 and nitric‐oxide‐synthase activity. All above‐mentioned furocoumarins showed significant effect on 5‐lipoxygenase (leukotriene C4) with IC50 values of < 15 μM. Imperatorin and isoimperatorin exhibited strong‐to‐medium inhibition on cyclooxygenase‐1‐ and cyclooxygenase‐2‐catalysed prostaglandin E2 release, with inhibition percentages similar to those of the reference drugs, indometacin and nimesulide, respectively. Of the three furocoumarins, only imperatorin caused a significant reduction of nitric oxide generation. Imperatorin and isoimperatorin can be classified as dual inhibitors, since it was evident that both cyclooxygenase and lipoxygenase pathways of arachidonate metabolism were inhibited by these compounds. However, selective inhibition of the 5‐lipoxygenase pathway is suggested to be the primary target of action of prantschimgin.

Inhibition by hydroxyachillin, sesquiterpene lactone fromTanacetum microphyllum, of PMA-induced mouse ear oedema

Abstract4-β-phorbol 12-myristate 13-acetate (PMA), when administered topically to mouse ear, induces a pronounced inflammatory response mediated by protein kinase C (PKC). Activation of PKC is implicated in the pathogenesis of inflammation, with phospholipase A2-dependent arachidonic acid release and eicosanoid production. We have investigated the effects of hydroxyachillin, a sesquiterpene lactone fromTanacetum microphyllum DC., on mouse ear oedema induced by PMA. The effects of this compound on swelling and other inflammatory parameters are described. Hydroxyachillin significantly (p≤0.01) inhibited ear swelling in a dose-dependent manner, and was as effective as the reference drugs. The PMA-induced vascular permeability was significantly (p≤0.05) reduced by hydroxyachillin at the highest dose (3 mg/ear). Histologically, the signs of inflammation were greatly reduced in the hydroxyachillin-treated ear lesions. These data suggest that hydroxyachillin is an effective anti-inflammatory agent in this model, and that the inhibition of PKC may be one of the mechanisms of hydroxyachillins effect.

Effects of compounds extracted from Santolina oblongifolia on TXB2 release in human platelets

A group of compounds isolated from the medicinal plant, Santolina oblongifolia, have been investigated for their effects on the release of platelet cyclo-oxygenase metabolite thromboxane A2 (measured as thromboxane B2) from ionophore-stimulated human platelets. These compounds, which are dual inhibitors of cyclo-oxygenase (prostaglandin E2) and lipoxygenase (leukotriene C4) activity in vitro, are: apigenin, luteolin, quercetin, herniarin, scopoletin, scopolin and aesculetin. All compounds assayed presented a dose-related response to thromboxane B2 release, with the percentages of inhibition being slightly lower than the reference drug, ibuprofen. Inhibition was more evident with the flavonoids. Our data support the inhibition of arachidonic acid metabolism as one of the mechanisms for which flavonoids and coumarins from S. oblongifolia exert their anti-inflammatory effect

Aggravation of adjuvant arthritis by carrageenan

1. We have studied the optimum conditions for the induction of adjuvant carrageenan-induced inflammation (ACII) in male Wistar rats with limited susceptibility to adjuvant arthritis (AA). 2. ACII was induced by intradermal injection of Freunds complete adjuvant (CFA), containing 10 mg/ml Mycobacterium tuberculosis, followed by a subplantar inoculation of the nonspecific inflammatory stimulus carrageenan at different times. 3. Data obtained indicate that the arthritis of rats inoculated with CFA is significantly increased by carrageenan, particularly when it is injected 14 days after the adjuvant. Arthritis enhancement was more evident in the joints of the leg that had been previously injected with carrageenan, and remained stable around the peak level for some weeks. The development of joint inflammation was associated histologically with the appearance of inflammatory cells in the synovial membrane of those animals. 4. We found that the injection of carrageenan aggravated the course of AA in general, but very significantly when administered at the moment of the appearance of arthritis (day + 14). This aggravation affected both the intensity of inflammation and the chronicity of the disease.

EFFECT OF SANTOLINA OBLONGIFOLIA ON ACII- IMMUNIZED ANIMALS

The therapeutic effect of organic extracts of Santolina oblongifolia in adjuvant-carrageenan-induced inflammation (ACII) in Wistar rats was investigated. The present study concerns the effect of the extracts on serum copper (Cu) and zinc (Zn) levels, and on hindpaw swelling and ankle joint widths of arthritic animals. Compared with controls, the arthritic animals showed an increase in serum Cu levels, while serum Zn was decreased. The altered levels of trace elements in arthritic animals were significantly normalized in the chronic phase of the disease after treatment with most of the extracts of S. oblongifolia. Additionally, administration of the extracts significantly decreased the clinical signs of inflammation. The results of the present investigation indicated that these extracts could offer a partial protective action against changes induced by ACII in Wistar rats.

Adjuvant-carrageenan-induced inflammation in mice.

1. A study was conducted to evaluate the optimum conditions for the induction of adjuvant-carrageenan-induced inflammation (ACII) in Swiss and DBA/1 mice. 2. ACII was induced in mice under experimental conditions similar to those known to be effective in rats. Mice were immunized by subdermal injection of Freunds complete adjuvant (CFA), followed by a subplantar inoculation of carrageenan at different times. 3. The diversities of the responses on ACII between both strains of mice and rats were observed. Data obtained indicate that DBA/1 mice showed an increase in hindpaw and ankle joint swelling, which was more evident on day 21 after carrageenan injection, independently of the time of application of this phlogistic agent. At this time, the histopathological changes were similar to those seen in rats, and were characterized by epidermal hyperplasia, with leukocyte infiltration and granuloma formation. 4. We found that DBA/1 mice, instead of rats, can be used for the evaluation of anti-inflammatory drug activity. However, it is advisable also to consult the histological data to establish whether the synovial changes revert.