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Four antibodies that inhibit interleukin (IL)-23 are approved for the treatment of moderate-to-severe plaque psoriasis. Here, we present non-clinical data comparing ustekinumab, guselkumab, tildrakizumab and risankizumab with regard to thermostability, IL-23 binding affinity, inhibitory-binding mode, in vitro potency and in vivo efficacy. Risankizumab and guselkumab exhibited 5-fold higher affinity for IL-23 and showed more potent inhibition of IL-23 signaling than ustekinumab and tildrakizumab. Risankizumab and guselkumab completely blocked the binding of IL-23 to IL-23Rα as expected, whereas tildrakizumab did not. In vitro, risankizumab and guselkumab blocked the terminal differentiation of TH17 cells in a similar manner, while tildrakizumab had minimal impact on TH17 differentiation. In a human IL-23-induced ear-swelling mouse model, risankizumab and guselkumab were more effective than ustekinumab and tildrakizumab at reducing IL-17, IL-22, and keratinocyte gene expression. Our results indicate that the four clinically approved antibodies targeting IL-23 differ in affinity and binding epitope. These attributes contribute to differences in in vitro potency, receptor interaction inhibition mode and in vivo efficacy in preclinical studies as described in this report, and similarly may affect the clinical performance of these drugs.

Background:Losartan, a blocker of the angiotensin II type I receptor, is an important part of the standard of care for diabetic nephropathy (DN). The obese ZSF-1 rats display many aspects of the clinical features of human Type II DN. The current study was designed to examine the treatment effects of losartan on obese ZSF-1 rats and to evaluate the impact of the onset of dosing on efficacy.Methods:The rats (7–10 weeks) underwent a right uninephrectomy (Unx) or sham surgery. Losartan (3, 10, 30 mg/kg) was dosed 3 or 9 weeks post-Unx and continued for 12 weeks.Results:Treatment with losartan reduced urinary protein excretion and blood lipids (triglyceride and cholesterol) dose-dependently in both studies. The glomerular filtration rate (GFR) was significantly lower in obese ZSF-1 rats compared with those in lean rats, and losartan was efficacious against this endpoint, in particular with the earlier onset of treatment. Losartan also decreased tubulointerstitial fibrosis, and similar to GFR, earlier treatment conferred beneficial actions even at the lowest dose of 3 mg/kg. Several urinary biomarkers were elevated in the obese ZSF-1 rats, but the levels of sTNFR1, TIMP-1, L-FABP and KIM-1 were the only markers decreased by losartan.Conclusions:Losartan was renoprotective in the ZSF-1 rats with DN, improving both the pathological and functional parameters of the disease. Importantly, the data also highlight the importance of treatment at earlier stages of the disease for protecting against decline in the GFR and the development of fibrosis.

Introduction The adenine model of kidney disease typically involves dietary delivery of adenine over several weeks. This model can be variable in its disease progression and can result in significant mortality. In the current study, the amount of adenine delivered to rats was controlled by utilizing oral gavage administration over a short period in an attempt to induce robust renal pathology while addressing variability and viability of the animals. Methods Adenine (150 or 200 mg/kg) was administered via oral gavage for 10 consecutive days, and assessed over a total of 20 days. Results Both adenine dose groups manifested pathophysiological features of kidney disease such as proteinuria, elevated serum creatinine and BUN, and tubulointerstitial fibrosis. The animals also displayed a decline in glomerular filtration rate. Renal mRNA expression of genes associated with injury, inflammation, and fibrosis (i.e., Col1a1, Acta2, Serpine1, Timp1, Fn-Eda, Tgfb1, Ccl2, Nlrp3, Aqp1 and Ccnd1) were elevated as were urinary biomarkers that have translational utility (i.e., clusterin, KIM-1, MCP-1, OPN, NGAL, B2M, calbindin, and cystatin C). All disease endpoints were more pronounced in the 200 mg/kg group, however, while measures of tissue fibrosis were sustained, there was partial recovery by day 20 in functional readouts. No mortality was observed in either dose group. Discussion Short-term delivery of adenine via precise gavage delivery induced a robust model with hallmarks of fibrotic kidney disease, had limited variance between animals, and no animal morbidity within the 20 days studied. This model represents a methodical alternative to long-term dietary dosing of adenine.

A novel 4-aminocyclopentapyrrolidine series of N-type Ca(2+) channel blockers have been discovered. Enantioselective synthesis of the 4-aminocyclopentapyrrolidines was enabled using N-tert-butyl sulfinamide chemistry. SAR studies demonstrate selectivity over L-type Ca(2+) channels. N-type Ca(2+) channel blockade was confirmed using electrophysiological recording techniques. Compound 25 is an N-type Ca(2+) channel blocker that produces antinociception in inflammatory and nociceptive pain models without exhibiting cardiovascular or motor liabilities.

The aim of this study was to compare a diverse set of peptide and small-molecule calcium channel blockers for inactivated-state block of native and recombinant N-type calcium channels using fluorescence-based and automated patch-clamp electrophysiology assays.The pharmacology of calcium channel blockers was determined at N-type channels in IMR-32 cells and in HEK cells overexpressing the inward rectifying K(+) channel Kir2.1. N-type channels were opened by increasing extracellular KCl. In the Kir2.1/N-type cell line the membrane potential could be modulated by adjusting the extracellular KCl, allowing determination of resting and inactivated-state block of N-type calcium channels. The potency and degree of state-dependent inhibition of these blockers were also determined by automated patch-clamp electrophysiology.N-type-mediated calcium influx in IMR-32 cells was determined for a panel of blockers with IC(50) values of 0.001-7 μM and this positively correlated with inactivated-state block of recombinant channels measured using electrophysiology. The potency of several compounds was markedly weaker in the state-dependent fluorescence-based assay compared to the electrophysiology assay, although the degree of state-dependent blockade was comparable.The present data demonstrate that fluorescence-based assays are suitable for assessing the ability of blockers to selectively interact with the inactivated state of the N-type channel.

Background and purpose: Acute activation of P2X7 receptors rapidly opens a non-selective cation channel. Sustained P2X7 receptor activation leads to the formation of cytolytic pores, mediated by downstream recruitment of hemichannels to the cell surface. Species- and single-nucleotide polymorphism-mediated differences in P2X7 receptor activation have been reported that complicate understanding of the physiological role of P2X7 receptors. Studies were conducted to determine pharmacological differences between human, rat and mouse P2X7 receptors. Experimental approach: Receptor-mediated changes in calcium influx and Yo-Pro uptake were compared between recombinant mouse, rat and human P2X7 receptors. For mouse P2X7 receptors, wild-type (BALB/c) and a reported loss of function (C57BL/6) P2X7 receptor were also compared. Key results: BzATP [2,3-O-(4-benzoylbenzoyl)-ATP] was more potent than ATP in stimulating calcium influx and Yo-Pro uptake at rat, human, BALB/c and C57BL/6 mouse P2X7 receptors. Two selective P2X7 receptor antagonists, A-740003 and A-438079, potently blocked P2X7 receptor activation across mammalian species. Several reported P2X1 receptor antagonists [e.g. MRS 2159 (4-[(4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl}-2-pyridinyl)azo]-benzoic acid), PPNDS and NF279] blocked P2X7 receptors. NF279 fully blocked human P2X7 receptors, but only partially blocked BALB/c P2X7 receptors and was inactive at C57BL/6 P2X7 receptors. Conclusions and implications: These data provide new insights into P2X7 receptor antagonist pharmacology across mammalian species. P2X7 receptor pharmacology in a widely used knockout background mouse strain (C57BL/6) was similar to wild-type mouse P2X7 receptors. Several structurally novel, selective and competitive P2X7 receptor antagonists show less species differences compared with earlier non-selective antagonists.

ATP-sensitive P2X7 receptors are localized on cells of immunological origin including peripheral macrophages and glial cells in the CNS. Activation of P2X7 receptors leads to rapid changes in intracellular calcium concentrations, release of the pro-inflammatory cytokine IL-1beta, and following prolonged agonist exposure, the formation of cytolytic pores in plasma membranes. Data from gene knockout studies and recently described selective antagonists indicate a role for P2X7 receptor activation in inflammation and pain. While several species selective P2X7 antagonists exist, A-804598 represents a structurally novel, competitive, and selective antagonist that has equivalent high affinity at rat (IC50 = 10 nM), mouse (IC50 = 9 nM) and human (IC50 = 11 nM) P2X7 receptors. A-804598 also potently blocked agonist stimulated release of IL-1beta and Yo-Pro uptake from differentiated THP-1 cells that natively express human P2X7 receptors. A-804598 was tritiated ([3H]A-804598; 8.1Ci/mmol) and utilized to study recombinant rat P2X7 receptors expressed in 1321N1 cells. [3H]A-804598 labeled a single class of high affinity binding sites (Kd=2.4 nM and apparent Bmax=0.56 pmol/mg). No specific binding was observed in untransfected 1321N1 cells. The pharmacological profile for P2X antagonists to inhibit [3H]A-804598 binding correlated with their ability to block functional activation of P2X7 receptors (r=0.95, P

The goal of this study was to identify a structurally distinct D(4)-selective agonist with superior oral bioavailability to our first-generation clinical candidate 1a (ABT-724) for the potential treatment of erectile dysfunction. Arylpiperazines such as (heteroarylmethyl)piperazine 1a, benzamide 2, and acetamides such as 3a,b exhibit poor oral bioavailability. Structure-activity relationship (SAR) studies with the arylpiperidine template provided potent partial agonists such as 4d and 5k that demonstrated no improvement in oral bioavailability. Further optimization with the (N-oxy-2-pyridinyl)piperidine template led to the discovery of compound 6b (ABT-670), which exhibited excellent oral bioavailability in rat, dog, and monkey (68%, 85%, and 91%, respectively) with comparable efficacy, safety, and tolerability to 1a. The N-oxy-2-pyridinyl moiety not only provided the structural motif required for agonist function but also reduced metabolism rates. The SAR study leading to the discovery of 6b is described herein.

P2X(7) receptor activation by ATP results in the release of IL-1beta and IL-18. Prolonged stimulation can lead to pore formation and cell death. In this study we pharmacologically characterized P2X(7) receptors on rat peritoneal cells (RPC) and on 1321N1 cells transfected with rat P2X(7) receptor (1321rP2X(7)-11).RPC were isolated from rats by lavage. P2X(7) agonist induced pore formation in RPC was measured by EtBr uptake. P2X(7)-stimulated pore formation and Ca(++) influx in 1321rP2X(7)-11 cells were measured by a fluorometric imaging plate reader. The effects of pyridoxal phosphate-6-azo phenyl -2'-4'-disulfonic acid (PPADS) on pore formation and Ca(++) influx were examined in both RPC and 1321rP2X(7)-11. P2X(7)-mediated IL-1beta release in RPC and the effect of PPADS were determined.RPC express functional P2X(7) receptors that were activated by ATP analogs with a rank order of potency of 2'- 3'-O-(4-Benzoylbenzoyl) adenosine 5'-triphosphate (BzATP)ATPalpha,beta-methylene ATP. Activation of P2X(7) receptors by BzATP was inhibited by PPADS. Similar results were also obtained in 1321rP2X(7)-11 cells. Activation of P2X(7) receptors on RPC resulted in IL-1 beta secretion, which was inhibited by PPADS.RPC express functional P2X(7) receptors that form pores and mediate the release of IL-1beta.

The goal of this study was to develop a new approach to study the pharmacology of the dopamine D 4 receptor that could be used in comparative studies with dopamine D 2 and D 3 receptors. Stable HEK-293 cell lines co-expressing recombinant human D 2L , D 3 or D 4 receptors along with Gα qo5 cDNA were prepared. Dopamine induced a robust, transient calcium signal in these cell lines with EC 50 s for D 2L , D 3 and D 4 of 18.0, 11.9 and 2.2 nM, respectively. Reported D 4 -selective agonists CP226269 and PD168077 were potent, partial D 4 agonists exhibiting 31–1700-fold selectivity for D 4 over D 3 or D 2 . Non-selective D 2 -like agonists apomorphine and quinpirole showed full efficacy but did not discriminate across the three receptors. D 3 -selective agonists 7-hydroxy-DPAT and PD128907 were potent but non-selective D 2 -like agonists. The reported D 3 partial agonist BP-897 exhibited minimal agonist activity at D 3 but was a potent D 3 antagonist and a partial D 4 agonist. Other D 2 -like antagonists, haloperidol, clozapine, and domperidone showed concentration-dependent inhibition of dopamine responses at all three receptors with K i ranging from 0.05 to 48.3 nM. The D 3 selective antagonist S33084 and D 4 -selective antagonist L-745870 were highly selective for D 3 and D 4 receptors with K b of 0.7 and 0.1 nM, respectively. Stable co-expression of D 2 -like receptors with chimeric Gα qo5 proteins in HEK-293 cells is an efficient method to study receptor activation in a common cellular background and an efficient method for direct comparison of ligand affinity and efficacy across human D 2L , D 3 and D 4 receptors.

Nonsteriodal anti-inflammatory drugs (NSAIDs) are efficacious for the treatment of pain associated with inflammatory disease. Clinical experience with marketed selective cyclooxygenase-2 (COX-2) inhibitors (celecoxib, rofecoxib, and valdecoxib) has confirmed the utility of these agents in the treatment of inflammatory pain with an improved gastrointestinal safety profile relative to NSAID comparators. These COX-2 inhibitors belong to the same structural class. Each contains a core heterocyclic ring with two appropriately substituted phenyl rings appended to adjacent atoms. Here, we report the identification of vicinally disubstituted pyridazinones as potent and selective COX-2 inhibitors. The lead compound in the series, ABT-963 [2-(3,4-difluoro-phenyl)-4-(3-hydroxy-3-methyl-butoxy)-5-(4-methanesulfonyl-phenyl)-2H-pyridazin-3-one], has excellent selectivity (ratio of 276, COX-2/COX-1) in human whole blood, improved aqueous solubility compared with celecoxib and rofecoxib, high oral anti-inflammatory potency in vivo, and gastric safety in the animal studies. After oral administration, ABT-963 reduced prostaglandin E2 production in the rat carrageenan air pouch model (ED50 of 0.4 mg/kg) and reduced the edema in the carrageenan induced paw edema model with an ED30 of 1.9 mg/kg. ABT-963 dose dependently reduced nociception in the carrageenan hyperalgesia model (ED50 of 3.1 mg/kg). After 14 days of dosing in the adjuvant arthritis model, ABT-963 had an ED(50) of 1.0 mg/kg in reducing the swelling of the hind paws. Magnetic resonance imaging examination of the diseased paws in the adjuvant model showed that ABT-963 significantly reduced bone loss and soft tissue destruction. ABT-963 is a highly selective COX-2 inhibitor that may have utility in the treatment of the pain and inflammation associated with arthritis.

Adenosine triphosphate (ATP) activates two receptor superfamilies, metabotropic P2Y and ionotropic P2X receptors. The P2X receptors are nonselective cation channels that are widely expressed on excitable cells including neurons, glia, and smooth muscle cells. The protocols in this unit are useful for evaluating ligands that interact with P2X receptors on native cells or that are cloned and expressed in recombinant heterologous cell systems. Calcium imaging methods are described for the pharmacological characterization of fast or slowly desensitizing P2X receptors. While these methods are readily applicable to a wide variety of ligand-gated ion channels, the protocols provided herein detail how they can be used to measure activation of homomeric P2X3 (fast desensitizing) and heteromeric P2X2/3 (slowly desensitizing) receptors. Appropriate agonists and/or calcium dyes can be substituted to assess activity at other P2X receptor subtypes. An additional protocol is provided for measuring P2X7 receptor-mediated pore formation in THP-1, a native human acute monocytic leukemia cell line that can be used to study homomeric P2X7 (non-desensitizing) receptors that are expressed on macrophages and microglial cells.

We disclose the design of a novel series of cyanoguanidines that are potent (IC(50) approximately 10-100 nM) and selective (> or = 100-fold) P2X(7) receptor antagonists against the other P2 receptor subtypes such as the P2Y(2), P2X(4), and P2X(3). We also found that these P2X(7) antagonists effectively reduced nociception in a rat model of neuropathic pain (Chung model). Particularly, analogue 53 proved to be effective in the Chung model, with an ED(50) of 38 micromol/kg after intraperitoneal administration. In addition compound 53 exhibited antiallodynic effects following oral administration and maintained its efficacy following repeated administration in the Chung model. These results suggest an important role of P2X(7) receptors in neuropathic pain and therefore a potential use of P2X(7) antagonists as novel therapeutic tools for the treatment of this type of pain.

A novel series of cyanoguanidine-piperazine P2X(7) antagonists were identified and structure-activity relationship (SAR) studies described. Compounds were assayed for activity at human and rat P2X(7) receptors in addition to their ability to inhibit IL-1 beta release from stimulated human whole blood cultures. Compound 27 possesses potent activity (0.12 microM) in this latter assay and demonstrates moderate clearance in-vivo.

Growing evidence supports a role for the immune system in the induction and maintenance of chronic pain. ATP is a key neurotransmitter in this process. Recent studies demonstrate that the glial ATP receptor, P2X7, contributes to the modulation of pathological pain. To further delineate the endogenous mechanisms that are involved in P2X7-related antinociception, we utilized a selective P2X7 receptor antagonist, A-438079, in a series of in vivo and in vitro experiments. Injection of A-438079 (10-300 micromol/kg, i.p.) was anti-allodynic in three different rat models of neuropathic pain and it attenuated formalin-induced nocifensive behaviors. Using in vivo electrophysiology, A-438079 (80 micromol/kg, i.v.) reduced noxious and innocuous evoked activity of different classes of spinal neurons (low threshold, nociceptive specific, wide dynamic range) in neuropathic rats. The effects of A-438079 on evoked firing were diminished or absent in sham rats. Spontaneous activity of all classes of spinal neurons was also significantly reduced by A-438079 in neuropathic but not sham rats. In vitro, A-438079 (1 microM) blocked agonist-induced (2,3-O-(4-benzoylbenzoyl)-ATP, 30 microM) current in non-neuronal cells taken from the vicinity of the dorsal root ganglia. Furthermore, A-438079 dose-dependently (0.3-3 microM) decreased the quantity of the cytokine, interleukin-1beta, released from peripheral macrophages. Thus, ATP, acting through the P2X7 receptor, exerts a wide-ranging influence on spinal neuronal activity following a chronic injury. Antagonism of the P2X7 receptor can in turn modulate central sensitization and produce antinociception in animal models of pathological pain. These effects are likely mediated through immuno-neural interactions that affect the release of endogenous cytokines.

ATP-sensitive P2X(7) receptors are localized on cells of immunological origin including glial cells in the central nervous system. Activation of P2X(7) receptors leads to rapid changes in intracellular calcium concentrations, release of the proinflammatory cytokine interleukin-1beta (IL-1beta), and following prolonged agonist exposure, cytolytic plasma membrane pore formation. P2X(7) knockout mice show reduced inflammation as well as decreased nociceptive sensitivity following peripheral nerve injury. A-740003 (N-(1-{[(cyanoimino)(5-quinolinylamino) methyl] amino}-2,2-dimethylpropyl)-2-(3,4-dimethoxyphenyl)acetamide) is a novel competitive antagonist of P2X(7) receptors (IC(50) values = 40 nM for human and 18 nM for rat) as measured by agonist-stimulated changes in intracellular calcium concentrations. A-740003 showed weak or no activity (IC(50) > 10 muM) at other P2 receptors and an array of other neurotransmitter and peptide receptors, ion channels, reuptake sites, and enzymes. A-740003 potently blocked agonist-evoked IL-1beta release (IC(50) = 156 nM) and pore formation (IC(50) = 92 nM) in differentiated human THP-1 cells. Systemic administration of A-740003 produced dose-dependent antinociception in a spinal nerve ligation model (ED(50) = 19 mg/kg i.p.) in the rat. A-740003 also attenuated tactile allodynia in two other models of neuropathic pain, chronic constriction injury of the sciatic nerve and vincristine-induced neuropathy. In addition, A-740003 effectively reduced thermal hyperalgesia observed following intraplantar administration of carrageenan or complete Freund's adjuvant (ED(50) = 38-54 mg/kg i.p.). A-740003 was ineffective in attenuating acute thermal nociception in normal rats and did not alter motor performance at analgesic doses. These data demonstrate that selective blockade of P2X(7) receptors in vivo produces significant antinociception in animal models of neuropathic and inflammatory pain.

A new series of dopamine D4 receptor agonists, 1-aryl-3-(4-pyridinepiperazin-1-yl)propanone oximes, was designed through the modification of known dopamine D4 receptor agonist PD 168077. Replacement of the amide group with a methylene-oxime moiety produced compounds with improved stability and efficacy. Structure-activity relationsips (SAR) of the aromatic ring linked to the N-4-piperazine ring confirmed the superiority of 2-pyridine as a core for D4 agonist activity. A two-methylene linker between the oxime group and the N-1-piperazine ring displayed the best profile. New dopamine D4 receptor agonists, exemplified by (E)-1-(4-chlorophenyl)-3-(4-pyridin-2-ylpiperazin-1-yl)propan-1-one O-methyloxime (59a) and (E)-1-(3-chloro-4-fluorophenyl)-3-(4-pyridin-2-ylpiperazin-1-yl)propan-1-one O-methyloxime (64a), exhibited favorable pharmacokinetic profiles and showed oral bioavailability in rat and dog. Subsequent evaluation of 59a in the rat penile erection model revealed in vivo activity, comparable in efficacy to apomorphine. Our results suggest that the oximes provide a novel structural linker for 4-arylpiperazine-based D4 agonists, possessing leadlike quality and with potential to develop a new class of potent and selective dopamine D4 receptor agonists.

2-[4-(3,4-Dimethylphenlyl)piperazin-1-ylmethyl]-1H benzoimidazole (A-381393) was identified as a potent dopamine D4 receptor antagonist with excellent receptor selectivity. [3H]-spiperone competition binding assays showed that A-381393 potently bound to membrane from cells expressing recombinant human dopamine D4.4 receptor (Ki=1.5 nM), which was 20-fold higher than that of clozapine (Ki=30.4 nM). A-381393 exhibited highly selective binding for the dopamine D4.4 receptor (>2700-fold) when compared to D1, D2, D3 and D5 dopamine receptors. Furthermore, in comparison to clozapine and L-745870, A-381393 exhibits better receptor selectivity, showing no affinity up to 10 microM for a panel of more than 70 receptors and channels, with the exception of moderate affinity for 5-HT2A (Ki=370 nM). A-381393 potently inhibited the functional activity of agonist-induced GTP-gamma-S binding assay and 1 microM dopamine induced-Ca2+ flux in human dopamine D4.4 receptor expressing cells, but not in human dopamine D2L or D3 receptor cells. In contrast to L-745870, A-381393 did not exhibit any significant intrinsic activity in a D4.4 receptor. In vivo, A-381393 has good brain penetration after subcutaneous administration. A-381393 inhibited penile erection induced by the selective D4 agonist PD168077 in conscious rats. Thus, A-381393 is a novel selective D4 antagonist that will enhance the ability to study dopamine D4 receptors both in vitro and in vivo.

A new class of agents with potential utility for the treatment of erectile dysfunction has been discovered, guided by the hypothesis that selective D4 agonists are erectogenic but devoid of the side effects typically associated with dopaminergic agents. The lead agent 2-(4-pyridin-2-ylpiperazin-1-ylmethyl)-1H-benzimidazole (1, ABT-724) was discovered by optimization of a series of benzimidazole arylpiperazines. This highly selective D4 agonist was found to be very potent and efficacious in vivo, eliciting penile erections in rats at a dose of 0.03 micromol/kg, with a positive response rate of 77% erectile incidence. Even at high doses, it was devoid of side effects in animal models of central nervous system behaviors, emesis, or nausea. The structure-activity relationship of the parent benzimidazole series leading to 1 is described, with the detailed in vitro and in vivo profiles described. Distinctive structural features were discovered that are associated with D4 selective agonism in this series of analogues.

Brief activation of the ATP-sensitive P2X(7) receptor (P2X(7)R) stimulates the maturation and release of interleukin 1beta (IL-1beta)in macrophages, whereas prolonged agonist activation induces the formation of cytolytic pores in cell membranes. The present study investigated potential downstream mechanisms associated with native human P2X(7)R activation in lipopolysaccharide and interferon-gamma differentiated THP-1 cells. 2,3-O-(4-Benzoylbenzoyl)-ATP (BzATP)-induced pore formation (EC(50) = 35 microM) was blocked by a selective P2X(7)R antagonist, 1[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-l-tyrosyl]-4-phenylpiperazine (KN-62) (IC(50) = 44 nM) and by pyridoxal phosphate-6-azophenyl-2-4-disulfonic acid (PPADS) (IC(50) = 344 nM). KN-62 and PPADS also blocked BzATP-induced IL-1beta release (EC(50) = 617 microM) with IC(50) values of 75 and 3500 nM, respectively. The selective p38 mitogen-activated protein kinase (MAPK) inhibitor, 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)-1H-imidazole (SB 202190), potently inhibited BzATP-induced pore formation (IC(50) = 75 nM) but did not alter P2X(7)-mediated calcium influx or IL-1beta release. SB 202190 and KN-62 also attenuated BzATP-mediated activation of phosphorylated p38 MAPK (pp38 MAPK). Two caspase inhibitors, YVAD (caspase 1) and DEVD (caspase 3), attenuated both BzATP-induced pore formation and IL-1beta release in a concentration-dependent fashion. Neither DEVD nor p38-MAPK inhibitors blocked cell membrane pore formation evoked by maitotoxin or by activation of human P2X(2a) receptors. These results indicate that P2X(7)R-mediated pore formation results from a coordinated cascade involving both the p38 MAPK and caspase pathways that is distinct from other cytolytic pore-forming mechanisms. In contrast, P2X(7)R-mediated IL-1beta release is dependent on caspase activity but not p38 MAPK. Taken together, these results support the hypothesis that downstream cellular signaling mechanisms, rather than channel dilation, mediate cytolytic pore formation after prolonged agonist activation, which underlies P2X(7) receptors.

A model of lung inflammation was developed in Brown Norway rats. Intense lung eosinophilia was induced by a single intravenous injection of Sephadex G-200 particles. The eosinophilia observed was preceded by an increase in cysteinyl leukotrienes found in lung lavage fluids. Theophylline and albuterol were tested in the model and found to be inactive, while dexamethasone was effective. Zileuton, a specific leukotriene inhibitor, was found to effectively inhibit leukotriene formation and the influx of eosinophils into the lungs of these Sephadex-treated animals. Studies with specific leukotriene D4 antagonists of the cysLT1 type receptor indicate that this leukotriene receptor is probably not involved directly in the eosinophilic inflammation. This model appears to be useful in characterizing potential anti-inflammatory effects of inhibitors by evaluating their ability to prevent eosinophil influx into the lung.