Mechanisms underlying the modulatory action of platelet activating factor (PAF) on the upregulation of kinin B1 receptors in the rat paw

Bradykinin release following trauma and hemorrhagic shock causes pulmonary alveolar leak in a rodent model

BACKGROUND

Hemorrhage accounts for 40% of the preventable death following severe injury. Activation of systemic coagulation produces bradykinin (BK), which may cause leak from the plasma to the extravascular space and to the tissues, which is part of the complex pathophysiology of trauma-induced end-organ injury. We hypothesize that BK, released during activation of coagulation in severe injury, induces pulmonary alveolar leak.

METHODS

Isolated neutrophils (PMNs) were pretreated with a specific BK receptor B2 antagonist HOE-140/icatibant and BK priming of the PMN oxidase was completed. Rats underwent tissue injury/hemorrhagic shock (TI/HS), TI/icatibant/HS, and controls (no injury). Evans blue dye was instilled, and the percentage leak from the plasma to the lung was calculated from the bronchoalveolar lavage fluid (BALF). CINC-1 and total protein were measured in the BALF, and myeloperoxidase was quantified in lung tissue.

RESULTS

The BK receptor B2 antagonist HOE140/icatibant inhibited (85.0 ± 5.3%) BK priming of the PMN oxidase ( p < 0.05). The TI/HS model caused activation of coagulation by increasing plasma thrombin-antithrombin complexes ( p < 0.05). Versus controls, the TI/HS rats had significant pulmonary alveolar leak: 1.46 ± 0.21% versus 0.36 ± 0.10% ( p = 0.001) and increased total protein and CINC-1 in the BALF ( p < 0.05). Icatibant given after the TI significantly inhibited lung leak and the increase in CINC-1 in the BALF from TI/icatibant/HS rats versus TI/HS ( p < 0.002 and p < 0.05) but not the total protein. There was no PMN sequestration in the lungs. Conclusions: This mixed injury model caused systemic activation of hemostasis and pulmonary alveolar leak likely due to BK release.

CONCLUSION

This mixed injury model caused systemic activation of hemostasis and pulmonary alveolar leak likely due to BK release.

LEVEL OF EVIDENCE

Original Article, Basic Science.

The role of kinin B1 and B2 receptors in the mouse model of oxazolone-induced atopic dermatitis

This study evaluated the role of kinin B₁ and B₂ receptors in the pre-clinical mouse model of oxazolone-induced atopic dermatitis. The B₁ R715 or B₂ HOE140 receptor antagonists were dosed at different schemes of treatment. After assessment of clinical lesion scores and pruritus, lesional skin samples were collected for histopathological analysis. The plasma extravasation and the expression of the metalloproteinase ADAMTS5 were also assessed. The immunopositivity for kinin receptors was evaluated in the skin, dorsal root ganglion (DRG), thoracic spinal cord and brain cortex sections. Marked upregulation of B₁ and B₂ receptors was observed in the skin of oxazolone-treated mice. The induction of atopic dermatitis led to a downregulation of both receptors in the DRG, without any alteration in the spinal cord and brain cortex. The repeated administration of HOE140 (50 nmol/kg; i.p.) partially inhibited the oxazolone-related pruritus, associated with a reduction of ADAMTS5 immunolabelling in the skin. Alternatively, R715 (438 nmol/kg; i.p.) produced a mild inhibition of plasma extravasation in oxazolone-challenged mice. Noteworthy, the repeated i.d. injection of R715 (30 nmol/site) or HOE140 (3 nmol/site) significantly reduced the histiocyte numbers, according to the histopathological analysis. Either B₁ or B₂ kinin antagonists, irrespective of the protocol of treatment, did not alter any other evaluated clinical or histological parameters. Data brings novel evidence about the role of kinin receptors in allergy-related conditions, such as atopic dermatitis. Further studies to test different protocols of treatment with kinin antagonists on in-depth cellular alterations underlying oxazolone-induced atopic dermatitis remain to be performed.

The kinin B1 and B2 receptors and TNFR1/p55 axis on neuropathic pain in the mouse brachial plexus

Tumour necrosis factor (TNF) and kinins have been associated with neuropathic pain-like behaviour in numerous animal models. However, the way that they interact to cause neuron sensitisation remains unclear. This study assessed the interaction of kinin receptors and TNF receptor TNFR1/p55 in mechanical hypersensitivity induced by an intraneural (i.n.) injection of rm-TNF into the lower trunk of brachial plexus in mice. The i.n. injection of rm-TNF reduced the mechanical withdrawal threshold of the right forepaw from the 3rd to the 10th day after the injection, indicating that TNF1/p55 displays a critical role in the onset of TNF-elicited neuropathic pain. The connection between TNF1/p55 and kinin B₁ and B₂ receptors (B₁R and B₂R) was confirmed using both knockout mice and mRNAs quantification in the injected nerve, DRG and spinal cord. The treatment with the B₂R antagonist HOE 140 or with B₁R antagonist des-Arg⁹-Leu⁸-BK reduced both BK- and DABK-induced hypersensitivity. The experiments using kinin receptor antagonists and CPM inhibitor (thiorphan) suggest that BK does not only activate B₂R as an orthosteric agonist, but also seems to be converted into DABK that consequently activates B₁R. These results indicate a connection between TNF and the kinin system, suggesting a relevant role for B₁R and B₂R in the process of sensitisation of the central nervous systems by the cross talk between the receptor and CPM after i.n. injection of rm-TNF.

Synthetic chalcones as potential tool for acute- and chronic-pain control

The purpose of this study was to validate the potential anti-hypersensitive activity of two chalcones, (2E)-1-(4-aminophenyl)-3-(4-nitrophenyl)prop-2-en-1-one (ANCh) and N-{4-[(2E)-3-(4-nitrophenyl)prop-2-enoil]phenyl}acetamide (AcANCh), by different models of acute and persistent pain in mice, besides in silico analysis. Molecules computational investigation for prediction of Lipinki's and Veber's rules to determine solubility, % absorption, drug likeness and toxicity liabilities was performed. Male and female C57BL/6 mice (20-30 g, n = 6) were used. Firstly, mice were pre-treated with the compounds ANCh or AcANCh and then submitted to the models of acute hypersensitivity by the intraplantar injection of different phlogistic agents. The mechanical sensitivity was assessed using von Frey hairs (0.6 g). The obtained data shows that both compounds presented important inhibitory effects on mechanical hypersensitivity induced by carrageenan (with oral bioavailability). The anti-hypersensitive effect was also accompanied by the interference in leukocyte migration, interleukin-1β (IL-1β) and tumour necrosis factor (TNF) levels reduction and by the absence of unspecific effects. Added to the in vivo results, the in silico analysis presented none violation in Lipinski's or Veber's rules, good probability to cell membrane permeability and oral bioavailability, positive values of drug likeness and few risk of computational toxicity. ANCh partially reduced the hypersensitivity induced by IL-1β and TNF, epinephrine and prostaglandin E₂ (PGE₂). AcANCh had similar effect, except for the absent of inhibition in PGE₂-injected mice. Both compounds were capable of reducing the mechanical hypersensitivity presented in all persistent models of hypersensitivity (inflammatory pain, chronic nerve constriction and cancer pain), with emphasis for ANCh. These results suggest that both chalcones could represent good strategies for the control of acute and chronic pain, without important side effects. ANCh seems to involve cell migration and cytokines production as the main mechanism, together with interference in PGE2 neuronal sensitization pathway. In vivo and in silico analyses reinforce the potential characteristics of the compounds to become future drugs.

Where's the Leak in Vascular Barriers? A Review

Edema is typically presented as a secondary effect from injury, illness, disease, or medication, and its impact on patient wellness is nested within the underlying etiology. Therefore, it is often thought of more as an amplifier to current preexisting conditions. Edema, however, can be an independent risk factor for patient deterioration. Improper management of edema is costly not only to the patient, but also to treatment and care facilities, as mismanagement of edema results in increased lengths of hospital stay. Direct tissue trauma, disease, or inappropriate resuscitation and/or ventilation strategies result in edema formation through physical disruption and chemical messenger-based structural modifications of the microvascular barrier. Derangements in microvascular barrier function limit tissue oxygenation, nutrient flow, and cellular waste removal. Recent studies have sought to elucidate cellular signaling and structural alterations that result in vascular hyperpermeability in a variety of critical care conditions to include hemorrhage, burn trauma, and sepsis. These studies and many others have highlighted how multiple mechanisms alter paracellular and/or transcellular pathways promoting hyperpermeability. Roles for endothelial glycocalyx, extracellular matrix and basement membrane, vesiculo-vacuolar organelles, cellular junction and cytoskeletal proteins, and vascular pericytes have been described, demonstrating the complexity of microvascular barrier regulation. Understanding these basic mechanisms inside and out of microvessels aid in developing better treatment strategies to mitigate the harmful effects of excessive edema formation.

Effects of the compounds resveratrol, rutin, quercetin, and quercetin nanoemulsion on oxaliplatin-induced hepatotoxicity and neurotoxicity in mice

Oxaliplatin (OXA) is a platinum compound widely used in the treatment of some solid tumors, especially colorectal cancer. Despite its usefulness, oxaliplatin-associated neurotoxicity represents the main dose-limiting factor of this drug, and until now, there is no suitable treatment. Chemotherapy with oxaliplatin also increases the rate of developing hepatic damages with inflammatory activity, termed chemotherapy-associated steatohepatitis (CASH). In the present study, we aimed to compare the effects of a series of antioxidant compounds on simultaneous development of oxaliplatin-induced hepato- and neurotoxicity in mice. Mice BALB/c were treated with oxaliplatin for 6 weeks, 10 mg/kg, intraperitoneally, resulting in mechanical allodynia and hepatic steatosis. We administered the following antioxidant compounds--rutin (RT) (20 mg/kg), resveratrol (RVS) (100 mg/kg), quercetin (QT) (20 mg/kg), and quercetin nanoemulsion (NQT) (20 mg/kg)--daily by gavage to BALB/c, and N-acetylcysteine (NAC) was used as positive control. Treatments with RSV, RUT, or NQT were able to prevent mechanical allodynia when compared to the OXA group, and this effect was associated with decreased c-Fos immunopositivity in the lumbar spinal cord. Regarding the effects on steatohepatitis, RVS, QT, and NQT almost completely reversed the mean liver weight increase induced by OXA. In accordance with these previous data, histological evaluation indicated attenuation of all features of hepatic steatosis evaluated in RSV, RUT, QT, and NQT groups. These compounds were able to reduce the immunopositivity for the apoptosis marker caspase-3. On the other hand, only QT and NQT treatments were able to reduce neutrophil migration measured by myeloperoxidase (MPO) activity. These results suggest that the compounds tested, RSV, RUT, QT, and NQT, would be useful for the clinical treatment of neuro- and hepatoxicity induced by oxaliplatin.

Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors

Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.

Superoxide generation and leukocyte accumulation: key elements in the mediation of leukotriene B₄-induced itch by transient receptor potential ankyrin 1 and transient receptor potential vanilloid 1

The underlying mechanisms of itch are poorly understood. We have investigated a model involving the chemoattractant leukotriene B₄ (LTB₄) that is up-regulated in common skin diseases. Intradermal injection of LTB4 (0.1 nmol/site) into female CD1 mice induced significant scratching movements (used as an itch index) compared with vehicle-injected (0.1% bovine serum albumin-saline) mice. Intraperitoneal transient receptor potential (TRP) channel antagonist treatment significantly inhibited itch as follows: TRP vanilloid 1 (TRPV1) antagonist SB366791 (0.5 mg/kg, by 97%) and the TRP ankyrin 1 (TRPA1) antagonists TCS 5861528 (10 mg/kg; 82%) and HC-030031 (100 mg/kg; 76%). Leukotriene B₄ receptor 2 antagonism by LY255283 (5 mg/kg i.p.; 62%) reduced itch. Neither TRPV1-knockout (TRPV1-KO) nor TRPA1-knockout (TRPA1-KO mice exhibited LTB₄-induced itch compared with their wild-type counterparts. The reactive oxygen species scavengers N-acetylcysteine (NAC; 204 mg/kg i.p.; 86%) or superoxide dismutase (SOD; 10 mg/kg i.p.; 83%) also inhibited itch. LTB4-induced superoxide release was attenuated by TCS 5861528 (56%) and HC-030031 (66%), NAC (58%), SOD (50%), and LY255283 (59%) but not by the leukotriene B4 receptor 1 antagonist U-75302 (9 nmol/site) or SB366791. Itch, superoxide, and myeloperoxidase generation were inhibited by the leukocyte migration inhibitor fucoidan (10 mg/kg i.v.) by 80, 61, and 34%, respectively. Myeloperoxidase activity was also reduced by SB366791 (35%) and SOD (28%). TRPV1-KO mice showed impaired myeloperoxidase release, whereas TRPA1-KO mice exhibited diminished production of superoxide. This result provides novel evidence that TRPA1 and TRPV1 contribute to itch via distinct mechanisms.

β-Caryophyllene inhibits dextran sulfate sodium-induced colitis in mice through CB2 receptor activation and PPARγ pathway

Cannabinoid receptor 2 (CB2) activation is suggested to trigger the peroxisome proliferator-activated receptor-γ (PPARγ) pathway, and agonists of both receptors improve colitis. Recently, the plant metabolite (E)-β-caryophyllene (BCP) was shown to bind to and activate CB2. In this study, we examined the anti-inflammatory effect of BCP in dextran sulfate sodium (DSS)-induced colitis and analyzed whether this effect was mediated by CB2 and PPARγ. Oral treatment with BCP reduced disease activity, colonic macro- and microscopic damage, myeloperoxidase and N-acetylglucosaminidase activities, and levels and mRNA expression of colonic tumor necrosis factor-α, IL-1β, interferon-γ, and keratinocyte-derived chemokine. BCP treatment also inhibited the activation of extracellular signal-regulated kinase 1/2, nuclear factor κB, IκB-kinase α/β, cAMP response element binding and the expression of caspase-3 and Ki-67. Moreover, BCP enhanced IL-4 levels and forkhead box P3 mRNA expression in the mouse colon and reduced cytokine levels (tumor necrosis factor-α, keratinocyte-derived chemokine, and macrophage-inflammatory protein-2) in a culture of macrophages stimulated with lipopolysaccharide. The use of the CB2 antagonist AM630 or the PPARγ antagonist GW9662 significantly reversed the protective effect of BCP. Confirming our results, AM630 reversed the beneficial effect of BCP on pro-inflammatory cytokine expression in IEC-6 cells. These results demonstrate that the anti-inflammatory effect of BCP involves CB2 and the PPARγ pathway and suggest BCP as a possible therapy for the treatment of inflammatory bowel disease.

Stability and local toxicity evaluation of a liposomal prilocaine formulation

This study reports a physicochemical stability evaluation of a previously reported liposomal prilocaine (PLC(LUV)) formulation (Cereda et al. J. Pharm. Pharmaceut. Sci. 7:235, 2004) before and after steam sterilization as well as its local toxicity evaluation. Prilocaine (PLC) was encapsulated into extruded unilamellar liposomes (LUVs) composed by egg phosphatidylcholine:cholesterol:alfa-tocopherol (4:3:0.07, mole %). Laser light-scattering analysis (p > 0.05) and thiobarbituric acid reaction (p > 0.05) were used to evaluate the liposomes physical (size) and chemical (oxidation) stability, respectively. The prilocaine chemical stability was followed by (1)H-nuclear magnetic resonance. These tests detected no differences on the physicochemical stability of PLC or PLC(LUV), sterilized or not, up to 30 days after preparation (p > 0.05). Finally, the paw edema test and histological analysis of rat oral mucosa were used to assess the possible inflammatory effects of PLC(LUV). PLC(LUV) did not evoke rat paw edema (p > 0.05), and no significant differences were found in histological analysis, when compared to the control groups (p > 0.05). The present work shows that PLC(LUV) is stable for a 30-day period and did not induce significant inflammatory effects both in the paw edema test and in histological analysis, giving supporting evidence for its safety and possible clinical use in dentistry.

Neuropathic pain-like behavior after brachial plexus avulsion in mice: the relevance of kinin B1 and B2 receptors

The relevance of kinin B(1) (B(1)R) and B(2) (B(2)R) receptors in the brachial plexus avulsion (BPA) model was evaluated in mice, by means of genetic and pharmacological tools. BPA-induced hypernociception was absent in B(1)R, but not in B(2)R, knock-out mice. Local or intraperitoneal administration of the B(2)R antagonist Hoe 140 failed to affect BPA-induced mechanical hypernociception. Interestingly, local or intraperitoneal treatment with B(1)R antagonists, R-715 or SSR240612, dosed at the time of surgery, significantly reduced BPA-evoked mechanical hypernociception. Intrathecal or intracerebroventricular administration of these antagonists, at the surgery moment, did not prevent the hypernociception. Both antagonists, dosed by intraperitoneal or intrathecal routes (but not intracerebroventricularly) 4 d after the surgery, significantly inhibited the mechanical hypernociception. At 30 d after the BPA, only the intracerebroventricular treatment effectively reduced the hypernociception. A marked increase in B(1)R mRNA was observed in the hypothalamus, hippocampus, thalamus, and cortex at 4 d after BPA and only in the hypothalamus and cortex at 30 d. In the spinal cord, a slight increase in B(1)R mRNA expression was observed as early as at 2 d. Finally, an enhancement of B(1)R protein expression was found in all the analyzed brain structures at 4 and 30 d after the BPA, whereas in the spinal cord, this parameter was augmented only at 4 d. The data provide new evidence on the role of peripheral and central kinin B(1)R in the BPA model of neuropathic pain. Selective B(1)R antagonists might well represent valuable tools for the management of neuropathic pain.

Low level laser therapy modulates kinin receptors mRNA expression in the subplantar muscle of rat paw subjected to carrageenan-induced inflammation

Low level laser therapy (LLLT) has been used clinically in order to treat inflammatory processes. In this work, we evaluated if LLLT alters kinin receptors mRNA expression in the carrageenan-induced rat paw edema. Experimental groups were designed as followed: A1 (Control-saline), A2 (Carrageenan-only), A3 (Carrageenan+laser 660 nm) and A4 (Carrageenan+laser 684 nm). Edema was measured by a plethysmometer. Subplantar tissue was collected for kinin receptors mRNA quantification by Real time-PCR. LLLT of both 660 and 684 nm wavelengths administrated 1 h after carrageenan injection was able to promote the reduction of edema produced by carrageenan. In the A2 group, B1 receptor expression presented a significantly increase when compared to control group. Kinin B1 receptor mRNA expression significantly decreased after LLLT's 660 or 684 nm wavelength. Kinin B2 receptor mRNA expression also diminished after both laser irradiations. Our results suggest that expression of both kinin receptors is modulated by LLLT, possibly contributing to its anti-inflammatory effect.

Anti-inflammatory effects of compounds alpha-humulene and (−)-trans-caryophyllene isolated from the essential oil of Cordia verbenacea

This study evaluated the anti-inflammatory properties of two sesquiterpenes isolated from Cordia verbenacea's essential oil, alpha-humulene and (-)-trans-caryophyllene. Our results revealed that oral treatment with both compounds displayed marked inhibitory effects in different inflammatory experimental models in mice and rats. alpha-humulene and (-)-trans-caryophyllene were effective in reducing platelet activating factor-, bradykinin- and ovoalbumin-induced mouse paw oedema, while only alpha-humulene was able to diminish the oedema formation caused by histamine injection. Also, both compounds had important inhibitory effects on the mouse and rat carrageenan-induced paw oedema. Systemic treatment with alpha-humulene largely prevented both tumor necrosis factor-alpha (TNFalpha) and interleukin-1beta (IL-1beta) generation in carrageenan-injected rats, whereas (-)-trans-caryophyllene diminished only TNFalpha release. Furthermore, both compounds reduced the production of prostaglandin E(2) (PGE(2)), as well as inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) expression, induced by the intraplantar injection of carrageenan in rats. The anti-inflammatory effects of alpha-humulene and (-)-trans-caryophyllene were comparable to those observed in dexamethasone-treated animals, used as positive control drug. All these findings indicate that alpha-humulene and (-)-trans-caryophyllene, derived from the essential oil of C. verbenacea, might represent important tools for the management and/or treatment of inflammatory diseases.

Targeting the bradykinin B1 receptor to reduce pain

The bradykinin B1 receptor is an inducible G-protein-coupled receptor. It is induced or upregulated at the site of inflammation or injury. A large body of preclinical data supports the development of B1 antagonists as novel therapeutics for the treatment of pain and inflammation. The necessary in vitro and in vivo drug discovery tools are currently available to evaluate novel B1 antagonists. Two major classes of small-molecule B1 antagonists, arylsulfonamide-based and biphenyl-based B1 antagonists, have been disclosed in the last few years.

Anti-edematogenic effects of velutinol A isolated from Mandevilla velutina: evidence for a selective inhibition of kinin B1 receptor-mediated responses

This study assesses the effects of compound velutinol A obtained from M. velutina in the rat paw edema induced by several phlogistic agents. Attempts were made to analyze how velutinol A is able to inhibit kinin B(1) receptor-mediated inflammatory responses. Velutinol A (100 nmol/paw) partially reduced (about 30%) the edema evoked by carrageenan (300 microg/paw). However, velutinol A (100 nmol/paw) failed to affect the edema induced by histamine (200 nmol/paw), substance P (30 nmol/paw), PAF (10 nmol/paw) or BK (3 nmol/paw). Interestingly, the edema caused by the selective kinin B(1) receptor agonist des-Arg(9)-BK (100 nmol/paw) in animals pre-treated with PAF or LPS was significantly inhibited by velutinol A (100 nmol/paw) (48 and 46%, respectively). A similar inhibition of des-Arg(9)-BK-induced edema after pre-treatment with PAF was obtained with the non-peptidic and selective B(1) receptor antagonist SSR 240612 (60 nmol/paw) (46%). In addition, the systemic administration of velutinol A (10 mg/kg, i.p.) or SSR 240612 (1 mg/kg, i.p.) also caused a significant reduction of des-Arg(9)-BK (100 nmol/paw)-induced edema in PAF-treated rats (51 and 43%, respectively). The results provide convincing evidence that velutinol A selectively blocks the edema responses mediated by B(1) receptor activation in vivo. This compound might represent a new non-peptidic and selective antagonist for kinin B(1) receptors.

Mechanisms underlying lipopolysaccharide-induced kinin B1 receptor up-regulation in the pig iris sphincter in vitro

Kinin B1 receptors are known to be highly induced after inflammatory stimuli in several biological systems. We report that incubation of pig iris sphincter with lipopolysaccharide from Escherichia coli caused a marked and time-related up-regulation of B1, accompanied by a reduction of B2 receptor-mediated contractile responses. The up-regulation of B1 receptors by lipopolysaccharide stimulation was decreased by the inhibitors of protein synthesis, cycloheximide and actinomycin D, and by dexamethasone and the nuclear factor-kappaB (NF-kappaB) inhibitor pyrrolidinedithiocarbamate (PDTC). In addition, lipopolysaccharide-induced up-regulation of B1 receptors in the pig iris sphincter was significantly reduced by the p38 inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580) and to a lesser extent by the extracellular signal-regulated kinases 1 and 2 (ERK1/2) blocker 2'-amino-3'-methoxyflavone (PD98059). Molecular biology experiments demonstrated that in vitro incubation with lipopolysaccharide resulted in a time-dependent and remarkable activation of NF-kappaB and of p38 and ERK1/2 mitogen-activated protein (MAP) kinases, in pig iris sphincter preparations. While attempting to verify how MAP kinases are part of the B1 receptor-activated signaling transduction pathways, we observed that PD98059 was able to markedly reduce the contraction induced by B1 receptor activation in lipopolysaccharide-pretreated pig iris sphincter muscle but that this response was only partially decreased by SB203580. Our results extend the previous evidence on the mechanisms underlying the B1 receptor upregulation processes and demonstrate for the first time how this takes place in an ocular tissue, the pig iris sphincter. It is therefore possible to define B1 receptors as therapeutic targets for the treatment of infectious and inflammatory alterations of the eye.

Cytokines and neutrophils as important mediators of platelet-activating factor-induced kinin B1 receptor expression

PAF injection into the rat paw is accompanied by the concomitant activation of NF-kappaB and neutrophil influx, which appears to be relevant to the up-regulation of kinin B1 receptors. Herein, we analyse the role of TNF-alpha and IL-1beta production for PAF-induced B1 receptor upregulation in the rat paw. Additionally, we evaluate how cytokine production and neutrophil migration fit into the temporal sequence of events leading to PAF-induced B1 receptor upregulation. In our experiments, treatment with PAF resulted in a marked increase of B1 receptor-mediated paw oedema and in situ production of TNF-alpha at 1 h and IL-1beta at 3 and 6 h later. B1 receptor-mediated paw oedema was significantly inhibited by anti-TNF-alpha antibody and by interleukin-1 receptor antagonist (IRA). TNF-alpha was necessary for the local PAF-induced IL-1beta production. NF-kappaB blocker PDTC prevented the production of both TNF-alpha and IL-1beta, indicating that cytokine production is NF-kappaB dependent. Depletion of neutrophils with an anti-PMN antibody prevented IL-1beta, but not TNF-alpha, production. Although both TNF-alpha and IL-1beta are relevant to functional B1 receptor upregulation, PAF-induced increase in B1 receptor mRNA was markedly suppressed by anti-TNF-alpha and, to a lesser extent, by IRA. B1 receptor mRNA expression was also prevented by the anti-PMN antibody. In conclusion, the activation of the TNF-alpha/neutrophil axis by PAF seems to be sufficient for B1 receptor mRNA production. However, the TNF-alpha/neutrophil axis is also necessary for IL-1beta production. These two processes might lead to the appearance of functional kinin B1 upregulation receptors in vivo after PAF treatment.

Assessment of TNFα contribution to the functional up-regulation of kinin B1 receptors in the mouse paw after treatment with LPS

It has been widely demonstrated that LPS is able to induce kinin B(1) receptor up-regulation throughout several models of inflammation. Using an in-vivo system in which LPS was administered systemically, we assessed the participation of the pro-inflammatory cytokine TNFalpha in the functional up-regulation of B(1) receptors in the mouse paw. Systemic treatment with LPS (10 microg/animal, i.v. 24 h before) resulted in a marked increase (about 5-fold) in the mouse paw edema induced by the selective B(1) receptor agonist des-Arg(9)-BK (50 nmol/paw) in both Swiss and C57/BL6 mice. The up-regulation of des-Arg(9)-BK-caused edema following LPS treatment was found to be greatly diminished in TNFalpha p55(-/-) receptor knockout mice. In addition, the paw edema evoked by des-Arg(9)-BK was significantly reduced when mice received the anti-TNFalpha antibody (100 [corrected] microg/kg, i.v.) 5 min before the LPS treatment. A similar inhibition of B(1) receptor-mediated paw edema was observed when mice were treated with thalidomide (30 mg/kg, s.c.) [corrected] a drug known for reducing TNFalpha synthesis, 5 min prior to LPS administration. ELISA experiment [corrected] revealed that TNFalpha serum levels were maximal at 1 h following LPS systemic treatment. Taken together, the present results suggest that the early production of the pro-inflammatory cytokine TNFalpha is probably responsible for driving the sequence of events involved in the functional up-regulation of B(1) receptors in the mouse paw.

Transient inflammatory response induced by apoptotic cells is an important mediator of melanoma cell engraftment and growth

Two murine melanoma cell lines, Tm1 and Tm5, were derived from a nontumorigenic lineage of pigmented murine melanocytes, melan-a. Both Tm1 and Tm5 are invariably tumorigenic in syngeneic mice when inoculated s.c. in doses higher than 10(4) cells; 10(3) or fewer cells rarely give rise to tumors. We demonstrate that subtumorigenic inocula of Tm1 or Tm5 cells (10(3)) as well as of a known murine melanoma cell line (B16F10) develop as vigorously growing tumor grafts only when coinoculated with apoptotic, but not necrotic cells. The presence of apoptotic cells correlates with a transient inflammatory infiltrate, composed mainly of neutrophils and macrophages. Kinin B1 receptor-deficient mice, which have impaired transmigration of neutrophils to inflamed tissues, had significant growth inhibition of subtumorigenic doses of melanoma cells coinjected with apoptotic cells. Using the same model, tumor take in athymic mice was similar to that seen in wild-type mice, suggesting that a T cell-dependent inflammatory response is not necessary to promote the survival and growth of subtumorigenic doses of melanoma cells. Taken together, our results describe how tumor engraftment and growth can be profoundly affected by microenvironmental alterations in response to the presence of apoptotic cells. Disrupting the delicate balance between apoptotic cells and leukocyte infiltration may provide potentially important insights for understanding and interfering with tumor cell viability during treatment with either gamma-radiation or apoptosis-inducing drugs.

Kinin B1 receptors: key G-protein-coupled receptors and their role in inflammatory and painful processes

Kinins are a family of peptides implicated in several pathophysiological events. Most of their effects are likely mediated by the activation of two G-protein-coupled receptors: B(1) and B(2). Whereas B(2) receptors are constitutive entities, B(1) receptors behave as key inducible molecules that may be upregulated under some special circumstances. In this context, several recent reports have investigated the importance of B(1) receptor activation in certain disease models. Furthermore, research on B(1) receptors in the last years has been mainly focused in determining the mechanisms and pathways involved in the process of induction. This was essentially favoured by the advances obtained in molecular biology studies, as well as in the design of selective and stable peptide and nonpeptide kinin B(1) receptor antagonists. Likewise, development of kinin B(1) receptor knockout mice greatly helped to extend the evidence about the relevance of B(1) receptors during pathological states. In the present review, we attempted to remark the main advances achieved in the last 5 years about the participation of kinin B(1) receptors in painful and inflammatory disorders. We have also aimed to point out some groups of chronic diseases, such as diabetes, arthritis, cancer or neuropathic pain, in which the strategic development of nonpeptidic oral-available and selective B(1) receptor antagonists could have a potential relevant therapeutic interest.

Kinin B1 receptor up-regulation after lipopolysaccharide administration: role of proinflammatory cytokines and neutrophil influx

Several studies have now clearly established the ability of LPS to induce bradykinin B(1) receptor up-regulation in vivo and the functional relevance of this up-regulation for the pathophysiological effects of LPS. Using an in vivo system in which LPS is injected locally into the rat paw, we have examined the potential contribution of proinflammatory cytokines, NF-kappaB activation, and neutrophil influx for the functional and molecular up-regulation of the bradykinin B(1) receptor. Treatment with LPS resulted in a rapid and sustained functional up-regulation of B(1) receptors in the rat paw that correlated with the increase in B(1) receptor mRNA levels. B(1) receptor up-regulation is preceded by the rapid activation of the transcription factor NF-kappaB and the production of proinflammatory cytokines, including TNF-alpha and IL-1beta. More importantly, blockade of NF-kappaB translocation, TNF-alpha, or IL-1beta prevented the functional and molecular up-regulation of B(1) receptors. Injection of LPS also induced the influx of neutrophils that followed the peak of cytokine production and associated with the persistent activation of NF-kappaB and functional B(1) receptor up-regulation. Blockade of neutrophil influx with platelet-activating factor receptor antagonists or cell adhesion molecule blockers prevented B(1) receptor up-regulation. Thus, by acting in cooperation and in a coordinated, timely manner, TNF-alpha, IL-1beta, neutrophils, and the transcription factor NF-kappaB are major and essential players in the ability of LPS to induce B(1) receptor expression in vivo.