A new method for measuring auricular inflammation in the mouse

Investigation of inflammatory mechanisms induced by croton oil in mouse ear

Croton oil is liquid at room temperature, with a pale-yellow color and spicy odor. It is commonly used in combination with phenol as a chemical peeling agent in dermatology, which reveals its caustic exfoliating effects. Topical use of croton oil at a high dose produces skin irritation, inflammation, swelling, pain, and even tumors. Therefore, croton oil has been widely used for inflammation, pain, and tumor related research, with different animal models having been established. However, mechanistic studies through which croton oil induces skin swelling, injury and activates tissue repair/regeneration are limited. The present study used croton oil to induce mouse ear edema and examined tissue responses 4 h after exposure. To this end, croton oil was applied to the ventral side of mouse ears, followed by tissue collection. Samples were analyzed by hematoxylin and eosin (H&E) staining, toluidine blue staining, and immunohistochemistry staining for myeloperoxidase (MPO) and matrix metalloproteinase-9 (MMP-9). Western blotting and ELISA were also carried out for MMP-9 together with unbiased proteomic analysis using mass-spectrometry. Results from our study demonstrated that as soon as 4 h of exposure to 2.5 % croton oil, the expression levels of MPO and MMP-9 in the dermis significantly increased compared to acetone-treated (vehicle) control ears, as did other inflammatory reactions such as swelling and neutrophil aggregation and infiltration. Subsequently, proteomic analysis confirmed that croton oil treatment resulted in significant upregulation of proteins such as myeloperoxidase (MPO), matrix metalloproteinase-9 (MMP-9), and matrix metalloproteinase-8 (MMP-8) in the ear skin. Interestingly, mouse ears treated with acetone vehicle showed differential expression of 2,478 proteins relative to naïve tissues; among those differentially expressed in acetone-treated samples were members of the phosphatidylinositol-glycan biosynthesis class N, T and U proteins (PIGN, PIGT, and PIGU). Overall, this work confirms the presence of neutrophil-derived MPO and MMP-9 and extends the body of knowledge to show that MMP-8 is also present during croton oil-mediated skin inflammation in the mouse ear; moreover, we find that acetone vehicle is not inert and has effects on the skin that should be considered moving forward.

Rosmarinus officinalis essential oil: A review of its phytochemistry, anti-inflammatory activity, and mechanisms of action involved

ETHNOPHARMACOLOGICAL RELEVANCE

Plant species Rosmarinus officinalis L. (Lamiaceae; Synonyms: Salvia rosmarinus Schleid. and Rosmarinus angustifolius Mill.) is a herb widely used worldwide. In local and traditional medicine, its used for inflammation-related diseases. Currently, studies report anti-inflammatory activity in its essential oil (EORO). However, to better understand EORO's anti-inflammatory activity its necessary to understand its phytochemistry and the signaling pathways affected by it. Hence, this review aimed to describe EORO phytochemical profile, ethnopharmacological uses, some biological activities of EORO will be described but emphasizing its anti-inflammatory potential and possible mechanisms of action involved.

MATERIALS AND METHODS

The research was performed using the databases Medline, Embase, BVS Regional Portal, Science Direct, CAPES Journals, and Scopus; using the keywords "Rosmarinus officinalis", "anti-inflammatory" and "essential oil". Additional information was gathered from related textbooks, reviews, and documents.

RESULTS AND DISCUSSION

Until now about 150 chemical compounds were identified in EORO samples, more frequently reported molecules were 1,8-cineole, α-pinene, and camphor. Studies suggest that the anti-inflammatory activity of EORO occur mainly through inhibition of NF-κB transcription and suppression of arachidonic acid cascade. Its antioxidant activity also aids by preventing injury caused by the reactive species of inflammation; its smooth muscle relaxant activity contributes to ameliorating airway inflammatory diseases. Lastly, toxicity assessments indicate low toxicity to EORO.

CONCLUSIONS

Current evidence indicates anti-inflammatory activity in EORO, supporting its ethnopharmacological uses in inflammatory-related diseases, and potential future applications. However, although considerable acute inflammatory models were tested, more chronic inflammatory models are needed; clinical studies are still absent, this may be due to the high doses needed for essential oils to exert pharmacological effects, but recent studies show this issue can be bypassed using the oil formulated as nanoemulsions to improve its bioavailability.

Anti-nociceptive and anti-inflammatory activity of sophocarpine

AIM OF THE STUDY

This study aimed to assess the anti-nociceptive and anti-inflammatory activity of sophocarpine in rodents.

MATERIALS AND METHODS

The anti-nociceptive effect was evaluated in two experimental animal models and anti-inflammatory effect in three animal models, and sophocarpine was given by tail vein injection for the above study.

RESULTS

Pretreatment with a single dose of sophocarpine (20 and 40 mg/kg) produced dose-dependent anti-nociceptive effects in thermally and chemically induced mouse pain models. Pretreatment with a single dose of sophocarpine also produced significant dose-dependent anti-inflammatory effects on carrageenan-induced rat hind paw edema (15 and 30 mg/kg), xylene-induced mouse ear edema (20 and 40 mg/kg) and acetic acid-induced mouse vascular permeation (20 and 40 mg/kg).

CONCLUSIONS

Sophocarpine possesses peripheral and central analgesic properties as well as anti-inflammatory activity on acute inflammatory processes.

The involvement of 5-HT3 and 5-HT4 receptors in two models of gastrointestinal transit in mice

Our aim was to study the involvement of 5-hydroxytryptamine (5-HT)(3) and 5-HT(4) receptors in two models of gastrointestinal transit (GIT) in mice: the 5-hydroxytryptophan (5-HTP)-induced diarrhea and intestinal inflammation produced by an irritant agent, croton oil (CO). 5-HTP (10 mg/kg) produced diarrhea that was significantly inhibited after pretreatment with ondansetron (5-HT(3) antagonist) or RS 39604 (5-HT(4) antagonist) (1-5 mg/kg). The GIT speed was increased after CO and 5-HTP administration. 5-HT(3-4) antagonists decreased GIT after 5-HTP-treatment but not after CO-treatment. Our results show that 5-HT(3) and 5-HT(4) receptors are involved in 5-HTP-induced diarrhea. This may be the reason why 5-HT(3-4) antagonists could be useful in the treatment of carcinoid syndrome diarrhea. 5-HT(3-4) antagonists were not effective in the modifications of GIT; nevertheless, they could be useful in the treatment of inflammatory bowel diseases because some symptoms as abdominal pain, discomfort or abnormal bowel function are modulated via 5-HT(3).

Antisense oligodeoxynucleotides to mu- and delta-opioid receptor mRNA block the enhanced effects of opioids during intestinal inflammation

Intestinal inflammation enhances the inhibitory effects of mu- and delta-opioids in the gut, possibly related to an increased receptor expression. We evaluated the effects of opioids after intraperitoneal administration of antisense oligodeoxynucleotides to mu- and/or delta-opioid receptor mRNA. Inflammation was induced in mice by intragastric administration of croton oil; gastrointestinal transit was assessed with charcoal and permeability with [51Cr]etylenediaminetetraacetate ([51Cr]EDTA). Baseline values were unaltered after antisense oligodeoxynucleotides. In controls, antisense oligodeoxynucleotides to mu-opioid receptor mRNA decreased the antitransit effects of morphine (27%) and [N-MePhe3D-Pro4]morphiceptin (PL017) (26%), and the reduction was significantly greater during inflammation (50% and 47%). A similar effect was observed on permeability (control: 41-21% decrease; inflamed: 66-45%). In both assays, antisense oligodeoxynucleotides to delta-opioid receptor mRNA also reduced the effects of [D-Pen2,5]enkephalin (DPDPE) in a higher percentage during inflammation (43-32% controls, 60-49% inflamed). We show that antisense oligodeoxynucleotides to mu- and/or delta-opioid receptor mRNA are efficiently blocking the intestinal effects of opioids during inflammation, suggesting that an increased transcription of these receptors in the gut mediates the enhanced effects of opioids during inflammation.

The inhibitory effects of alpha(2)-adrenoceptor agonists on gastrointestinal transit during croton oil-induced intestinal inflammation

1. The peripheral effects of alpha(2)-adrenoceptor agonists were investigated in a model of intestinal inflammation induced by intragastric administration of croton oil (CO). Our hypothesis was that inflammation would 'sensitize' adrenoceptors in peripheral and/or central terminals of myenteric and submucous plexus neurones, and enhance systemic effects of alpha(2)-adrenoceptor agonists. 2. Male swiss CD-1 mice, received intragastrically CO (0.05 ml), castor oil (CA, 0.1 ml) or saline (SS) 3 h before the study: gastrointestinal transit (GIT) was evaluated 20 min afterwards with a charcoal meal. The presence of inflammation was assessed by electron microscopy. 3. The intragastric administration of CA or CO caused an increase in GIT and weight loss, but only CO induced an inflammatory response. Both clonidine (imidazoline1/alpha(2)-agonist) and UK-14304 (alpha(2)-agonist) produced dose-related inhibitions of GIT in all groups. During inflammatory diarrhoea (CO), potencies of systemic (s.c.) clonidine and UK-14304 were significantly increased 3.5 and 2.1 times, respectively, while potencies remained unaltered in the presence of diarrhoea without inflammation (CA). The effects were reversed by administration (s.c.) of receptor-specific adrenoceptor antagonists, but not by naloxone. 4. Clonidine was 8.3 (SS) and 2.8 (CO) times more potent when administered intracerebroventricularly (i.c.v.), than when administered s.c. Inflammation of the gut did not alter the potency of i.c.v. clonidine, demonstrating that enhanced effects of s.c. clonidine are mediated by peripheral receptors. During inflammation, i.c.v. efaroxan did not antagonize low doses of s.c. clonidine (ED20 and ED50S), but partially reversed ED80S, further supporting the peripheral effects of the agonists in CO treated animals. 5. The results demonstrate that inflammation of the gut enhances the potency of alpha(2)-adrenoceptor agonists by a peripheral mechanism. The results also suggest that the inflammatory response induces an up-regulation or sensitization of alpha(2)-adrenoceptors and/or imidazoline receptors.

Characterization and pharmacological modulation of antigen-induced peritonitis in actively sensitized mice

1. The intraperitoneal (i.p.) injection of 1 or 10 micrograms ovalbumin to sensitized Balb/c mice led to an acute histamine release, firstly evidenced 1 min after the challenge and returning to basal levels 30 min thereafter. This phenomenon was unaccompanied by protein extravasation. A dose-dependent increase in the amounts of immunoreactive leukotriene (LT) C4 and LTB4 was observed in the peritoneal washing from sensitized mice 6 h after 1 or 10 micrograms ovalbumin administration. In separate experiments, the i.p. administration of 1 mg activated zymosan to non-immunized mice was followed by a marked protein extravasation, and by immunoreactive LTC4 and LTB4, but not histamine, release in mouse peritoneum 1 h after its injection. 2. Mediator release in the mice peritoneal cavity was concomitant with a transient neutrophil infiltration, which peaked at 6 h and returned to basal levels therefore. An intense eosinophil accumulation starting at 24 h, peaking at 48 h and returning to basal values at 164 h, was also observed. 3. Ovalbumin (1 microgram)-induced eosinophilia, observed at 24 h, was reduced by the pretreatment of the animals with dexamethasone (1 mg kg-1, s.c.) or with the 5-lipoxygenase inhibitor, BWA4C (20 mg kg-1, s.c.), whereas indomethacin (2 mg kg-1, s.c.) and the platelet-activating factor (PAF)-antagonist SR 27417 (10 mg kg-1, s.c.) were ineffective. These results indicate that metabolites of arachidonic acid of lipoxygenase pathway, but not cyclo-oxygenase derivatives or PAF, mediate antigen-induced eosinophil accumulation in the mouse peritoneum. 4. The histamine HI receptor antagonist drug, cetirizine (15-30 mg kg-1, s.c.) markedly reduced ovalbumin-induced eosinophil accumulation under conditions where terfenadine was ineffective, suggesting that the effect of cetirizine was not related to the inhibition of the H1 receptor effects of histamine.5. The immunosuppressive agent, FK-506 (1-2 mg kg-1, s.c.) and the protein synthesis inhibitor,cylcoheximide, when administered either in situ (0.06 ng/cavity) or systemically (5 mg kg-1, s.c.),prevented antigen-induced eosinophil accumulation in the mouse peritoneum, contributing to the concept that substances (probably cytokines) originating from lymphocytes may be involved in the modulation of the eosinophilotactic response in this model.6. The results of the present study indicate that the i.p. administration of ovalbumin to actively sensitized mice induced late eosinophil accumulation in the peritoneal cavity. This phenomenon, which may be in part mediated by the release of lipoxygenase metabolites and/or by newly generated factors,such as T-lymphocytes-derived eosinophilotactic cytokines, offers an interesting tool to investigate the mechanism of action of anti-allergic and anti-inflammatory drugs.