Involvement of guanylate cyclase and potassium channels on the delayed phase of mouse carrageenan-induced paw oedema

Involvement of the nitric oxide/soluble guanylate cyclase pathway in the anti-oedematogenic action of Pfaffia glomerata (Spreng) Pedersen in mice

Pfaffia glomerata is used in southern American countries against inflammatory diseases. We have explored the ability of a crude hydroalcoholic extract of P. glomerata root (HEPG) to prevent the oedematogenic action of several inflammatory agents in mice. We have examined also the duration of its effects and the mechanisms involved. The oral or intraperitoneal treatment of mice with HEPG (1, 10, 30, 100 or 300 mg kg−1) reduced, in a dose-dependent manner, carrageenan-induced paw oedema in the early (1–4 h) and late (48 h) periods. In the early period, the ID50 value (the median dose that caused 50% inhibition) of HEPG was 60.5 (28.5–128.71) and 20.4 (14.8–28.3) mg kg−1 after oral and intraperitoneal administration, respectively. This effect was still evident when HEPG was administered up to 6 h before carrageenan. HEPG inhibited also paw oedema induced by histamine, serotonin, bradykinin, substance P and bacterial lipopolysaccharide. In addition, oral administration of HEPG increased the levels of nitrate and nitrite in the blood of mice. Further, its anti-oedematogenic action against carrageenan was prevented fully by NG nitro-L-arginine-methyl-ester (10 mg kg−1, s.c.), as well as by methylene blue (20 mg kg−1, s.c.) or 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (2 mg kg−1, s.c.). The results indicated that stimulation of endogenous production of nitric oxide, followed by soluble guanylate cyclase activation, was implicated in the anti-oedematogenic action of HEPG.

Lack of lymphatic vessel phenotype in LYVE-1/CD44 double knockout mice

Lymphatic vessels play a key role in maintaining tissue-fluid homeostasis, immune surveillance and metastasis. The hyaluronan receptor, LYVE-1, is widely used as a molecular marker for adult and embryonic lymphatic endothelium, but its physiological functions have not yet been established in vivo. In agreement with a recent report, LYVE-1(-/-) mice, which are healthy and fertile, do not display any defects related to congenital abnormalities of the lymphatic system. One hypothesis for the absence of a phenotype in LYVE-1 null mice is that other hyaluronan receptors, such as CD44, may compensate for LYVE-1. To test this hypothesis, we created LYVE-1/CD44 double knockout mice with appropriate littermate controls. Lymphatic vessel structure and function, as determined by histological methods and intravital microscopy, show that LYVE-1(-/-), CD44(-/-) and LYVE-1(-/-)/CD44(-/-) mice are indistinguishable from wild-type mice under normal conditions. Furthermore, resolution of carrageenan-induced paw edema is comparable in all genotypes. However, LYVE-1(-/-)/CD44(-/-) mice exhibit increased edema formation in a carrageenan-induced paw inflammation model compared to wild-type mice, but not to LYVE(-/-) or CD44(-/-) mice. These data suggest that LYVE-1 and CD44 are not required for the formation or function of lymphatics, but do not rule out a role for LYVE-1 in inflammation.

Nitric oxide and vascular reactivity in sepsis

Sepsis and septic shock are major causes of morbidity and mortality in critically ill patients. Sepsis and septic shock induce a profound fall in the peripheral vascular tone. NO has been implicated as a key player in vascular changes of sepsis and septic shock. In this brief review, two points are focused in greater detail: first, the involvement of guanylate cyclase and potassium channels in NO vascular effects in sepsis; second, the role played by NO and its two effectors in the long-lasting modifications of vascular reactivity in sepsis. Some recent developments in the area are reviewed.

Apoptotic mimicry: phosphatidylserine liposomes reduce inflammation through activation of peroxisome proliferator-activated receptors (PPARs) in vivo

BACKGROUND AND PURPOSE

Recently, there has been much attention paid to understanding the molecular mechanisms underlying apoptosis and the functional consequences of apoptotic body clearance by phagocytes. In an attempt to investigate this latter aspect, the present study evaluated the anti-inflammatory effects of in vivo administration of phosphatidylserine (PS) liposomes, a well-characterised membrane component expressed during apoptosis. The participation of peroxisome proliferator-activated receptors (PPARs) in PS-mediated effects was also investigated.

EXPERIMENTAL APPROACH

The anti-inflammatory effect of PS liposomes on the delayed phase of carrageenan mouse paw oedema was studied. PS liposomes were injected at different doses and times, after carrageenan. Hind paws were collected for evaluation of interleukin-1beta (IL-1beta) levels, myeloperoxidase (MPO) and N-acetyl-glucosaminidase (NAG) activities and Evans blue dye leakage. Participation of PPAR pathways was explored by using PPAR antagonists (BADGE and GW9662).

KEY RESULTS

Administration of PS, but not phosphatidylcholine (PC), liposomes (20-200 mg kg(-1), i.p., 8 h after carrageenan) reduced the paw oedema in a dose-dependent manner. PS liposomes were effective even when administered 24 and 48 h after carrageenan, a time at which indomethacin (1 mg kg(-1), i.p.) had no significant effects. Carrageenan-induced Evans blue leakage and IL-1beta production was decreased in PS-treated paws. The PPAR antagonists (BADGE and GW9662) partially prevented the anti-inflammatory effects of PS administration.

CONCLUSIONS AND IMPLICATIONS

PS liposomes have anti-inflammatory effects in vivo that are at least partly dependent on PPAR activation. Therapeutic strategies mimicking apoptosis may be useful for the treatment of inflammatory disorders.

Selective in vivo anti-inflammatory action of the galactolipid monogalactosyldiacylglycerol

The thermophilic blue-green alga ETS-05 colonises the therapeutic thermal muds of Abano and Montegrotto, Italy. Following the isolation, purification and identification of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulphoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol from ETS-05, we here examine their in vivo anti-inflammatory activities. MGDG, DGDG and SQDG inhibit croton-oil-induced ear oedema in the mouse in a dose-dependent manner. Inhibition by MGDG is greater than that of the reference drug, betamethasone 17,21-dipropionate, and is largely abrogated following acyl group saturation. SQDG is the least potent of these glycoglycerolipids, and shows an early transient effect. In the in vivo carrageenan-induced paw oedema model in the mouse, the inhibitory effects are again dose dependent, with an enhanced efficacy of MGDG over DGDG, SQDG and the reference drug, indomethacin. These compounds are all less toxic than indomethacin. The selective and enhanced inhibitory effects of MGDG over DGDG indicate the mechanisms behind these in vivo anti-inflammatory actions.