Platelet activating factor is a lipid mediator of inflammation, and in recent decades, it has emerged as an important factor in tumor outcomes. Platelet activating factor acts by specific binding to its receptor, which is present in both tumor cells and cells that infiltrate tumors. Pro-tumorigenic effects of platelet activating factor receptor in tumors includes promotion of tumor cell proliferation, production of survival signals, migration of vascular cells and formation of new vessels and stimulation of dendritic cells and macrophages suppressor phenotype. In experimental models, blocking of platelet activating factor receptor reduced tumor growth and increased animal survival. During chemotherapy and radiotherapy, tumor cells that survive treatment undergo accelerated proliferation, a phenomenon known as tumor cell repopulation. Work from our group and others showed that these treatments induce overproduction of platelet activating factor-like molecules and increase expression of its receptor in tumor cells. In this scenario, antagonists of platelet activating factor markedly reduced tumor repopulation. Here, we note that combining chemo- and radiotherapy with platelet activating factor antagonists could be a promising strategy for cancer treatment.

OBJETIVO: Investigar o papel do óxido nítrico (NO) no influxo celular (IC) e a incapacitação articular (IA) na artrite por zymosan (AZy). MÉTODOS: Ratos Wistar receberam injeção de Zy (1mg) no joelho direito. Grupos-controles receberam salina. A IA foi avaliada pelo Teste de incapacitação articular para ratos. Após sacrifício, o IC e a liberação de PGE2 foram avaliados no lavado articular. Avaliou-se o edema pela diferença peso úmido/peso seco do tecido articular. Grupos foram tratados i.p. com L-NAME - inibidor de sintases de NO (NOS) (LN=30-300mg/kg) ou aminoguanidina (AG= 30-300mg/kg) - inibidor seletivo de iNOS 30 min antes ou 2 h após o Zy. RESULTADOS: O pré-tratamento com L-NAME ou AG inibiu de forma dose-dependente a IA e o IC, mas não o edema ou a liberação de PGE2, sendo máximo para LN ou AG (100mg/kg). L-arginina (1g/kg) co-injetada com LN (100mg/kg) reverteu a inibição da IA e do IC. D-NAME (100mg/kg) não teve efeito. Co-injeção de naloxona (antagonista opióide) reverteu o efeito de LN e AG sobre a IA. A pressão arterial média elevou-se (p<0,01) após LN (100mg/kg), mas não com AG (100mg/kg). LN e AG (100mg/kg) dados 2 h após Zy não tiveram efeito. Azul de metileno (inibidor de GMPc), e não hemoglobina (scavenger de NO), reduziu IA e IC (p<0,01). Nitroprussiato de sódio (doador de NO) dado 2 h após Zy, reduziu a IA, mas não o IC (p<0,01). CONCLUSÕES: A antinocicepção na AZy por inibição da iNOS só ocorre como pré-tratamento, por efeito antiinflamatório via GMPc, independentemente de NO exógeno ou de PGE2, associada à liberação de opióides endógenos. Um doador de NO produz analgesia na AZy. Enfim, o trabalho demonstra efeito analgésico de um doador de NO em um modelo de periartrite, abrindo a perspectiva do uso dessas substâncias em humanos.

OBJECTIVE: To study the role of nitric oxide (NO) in the cell influx (CI) and the articular incapacitation (AI) in the zymosan induced-arthritis (ZyA). METHODS: Wistar rats received 1 mg of zymosan (Zy) into the right knee joint, and controls received saline. The AI was evaluated by the Test for AI in rats. After sacrifice, the CI and the release of prostaglandin E2 (PGE2) were assessed in the joint exudate. The joint edema was measured by the wet/dry weight ratio of the articular tissue. Groups were treated i.p. with L-NAME - NO synthase (NOS) inhibitor (LN = 30-300 mg/kg) or aminoguanidine (AG = 30-300 mg/kg) - selective iNOS inhibitor - 30 minutes before or 2 hours after the Zy. RESULTS: Pretreatment with L-NAME or AG dose-dependently inhibited the AI and the CI, but not altering edema or PGE2 release, being maximal for the 100 mg/kg doses of L-N and AG. Coinjection of L-arginine (1g/kg) and LN (100 mg/kg) reversed the inhibition of the AI and of the CI. D-NAME (100 mg/kg) had no effect. Coinjection of naloxone (opioid antagonist) reversed LN or AG effect on the AI. Mean arterial pressure increased (p<0,01) with LN (100 mg/kg), but not with AG (100 mg/ kg). LN and AG (100 mg/kg) given 2 hours after the Zy had no effect. Methylene blue (GMPc inhibitor), but not hemoglobin (NO scavenger) reversed AI and CI (p<0,01). Sodium nitroprusside (NO donor) given 2 hours after Zy reduced significantly AI, but not CI (p<0,01). CONCLUSIONS: The antinociceptive effect of iNOS inhibition in ZyA happens only with a prophylactic administration, due to an anti-inflammatory effect via GMPc, independently of exogenous NO or PGE2 release, but is associated to endogenous opioid release. The administration of an NO donor produces analgesia in ZyA.

We summarize here the main characteristics of a novel model of pulmonary hypersensitivity. Mice were immunized with a subcutaneous implant of a fragment of heat solidified chicken egg white and 14 days later challenged with ovalbumin given either by aerosol or by intratracheal instillation. This procedure induces a persistent eosinophilic lung inflammation, a marked bone marrow eosinophilia, and Th2-type isotypic profile with histopathological findings that resemble human asthma. Further, this model is simple to perform, reproducible in different strains of mice, does not require adjuvants nor multiple boosters. Based on these characteristics we propose it as a suitable murine model of allergic eosinophilic lung inflammation.