Complement factor B is critical for sub-RPE deposit accumulation in a model of Doyne honeycomb retinal dystrophy with features of age-related macular degeneration

EFEMP1 R345W is a dominant mutation causing Doyne honeycomb retinal dystrophy/malattia leventinese (DHRD/ML), a rare blinding disease with clinical pathology similar to age-related macular degeneration (AMD). Aged Efemp1  R345W/R345W knock-in mice (Efemp1ki/ki) develop microscopic deposits on the basal side of retinal pigment epithelial cells (RPE), an early feature in DHRD/ML and AMD. Here, we assessed the role of alternative complement pathway component factor B (FB) in the formation of these deposits. RNA-seq analysis of the posterior eyecups revealed increased unfolded protein response, decreased mitochondrial function in the neural retina (by 3 months of age) and increased inflammatory pathways in both neural retina and posterior eyecups (at 17 months of age) of Efemp1ki/ki mice compared with wild-type littermate controls. Proteomics analysis of eye lysates confirmed similar dysregulated pathways as detected by RNA-seq. Complement activation was increased in aged Efemp1ki/ki eyes with an approximately 2-fold elevation of complement breakdown products iC3b and Ba (P < 0.05). Deletion of the Cfb gene in female Efemp1ki/ki mice partially normalized the above dysregulated biological pathway changes and oral dosing of a small molecule FB inhibitor from 10 to 12 months of age reduced sub-RPE deposits by 65% (P = 0.029). In contrast, male Efemp1ki/ki mice had fewer sub-RPE deposits than age-matched females, no elevation of ocular complement activation and no effect of FB inhibition on sub-RPE deposits. The effects of FB deletion or inhibition on Efemp1ki/ki mice supports systemic inhibition of the alternative complement pathway as a potential treatment of dry AMD and DHRD/ML.

Discovery of 4-((2S,4S)-4-Ethoxy-1-((5-methoxy-7-methyl-1H-indol-4-yl)methyl)piperidin-2-yl)benzoic Acid (LNP023), a Factor B Inhibitor Specifically Designed To Be Applicable to Treating a Diverse Array of Complement Mediated Diseases

The alternative pathway (AP) of the complement system is a key contributor to the pathogenesis of several human diseases including age-related macular degeneration, paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), and various glomerular diseases. The serine protease factor B (FB) is a key node in the AP and is integral to the formation of C3 and C5 convertase. Despite the prominent role of FB in the AP, selective orally bioavailable inhibitors, beyond our own efforts, have not been reported previously. Herein we describe in more detail our efforts to identify FB inhibitors by high-throughput screening (HTS) and leveraging insights from several X-ray cocrystal structures during optimization efforts. This work culminated in the discovery of LNP023 (41), which is currently being evaluated clinically in several diverse AP mediated indications.

Amount of Mononuclear Phagocyte Infiltrate Does Not Predict Area of Experimental Choroidal Neovascularization (CNV)

Purpose: Mononuclear phagocytes (MNPs) are present in neovascular age-related macular degeneration (nv AMD) which is also called choroidal neovascularization (CNV). The number and phenotype of the MNPs depend upon the local environment in the CNV and effect of nv AMD therapy. We investigated ocular cell infiltration and conditions that modulate angiogenesis in a laser-induced mouse CNV model.

Methods: We developed assays to quantify MNPs in our established mouse CNV model. One MNP assay quantified the number of subretinal cells peripheral to the CNV lesions. A second assay semiquantitatively assesses the number of MNPs localized to the CNV lesion. We used these assays to measure the effect of toll-like receptor-2 (TLR-2) activation, anti-vascular endothelial growth factor (VEGF) therapy, and chemokine (C-C motif) ligand 2 (Ccl2) genetic deletion on MNP infiltration after laser injury.

Results: Laser injury induced blood vessel growth and infiltration of MNPs. Systemic administration of a TLR-2 activating peptide increased laser-induced CNV area, MNP cell numbers, and MNP density over the CNV lesions. Systemic administration of a VEGF antibody reduced CNV area, while Ccl2 genetic deletion increased CNV area. Despite the change in amount of angiogenesis, MNP infiltration was, surprisingly, unchanged in these 2 conditions.

Conclusions: MNP quantification provides biological insights for candidate AMD therapies. The number of infiltrating MNP cells does not correlate with the amount of laser-induced CNV area.

Induction of Ocular Complement Activation by Inflammatory Stimuli and Intraocular Inhibition of Complement Factor D in Animal Models

Purpose

Genome-wide association studies suggest a role for the complement system in age-related macular degeneration (AMD). We characterized ocular complement activation and evaluated a complement factor D (FD) neutralizing antibody.

Methods

Mice were treated with toll-like receptor (TLR) ligands, intravitreal injection (IVT), or corneal debridement. Levels of complement proteins and mRNA were measured. A FD neutralizing antibody was administered IVT into eyes of rabbits that were challenged with LPS (lipopolysaccharide) administered intravenously.

Results

Levels of C3 and factor B (FB) mRNA and protein in the eye were increased following intraperitoneal injection of TLR4 ligand LPS. Increased levels of C3 and FB breakdown products were observed in both eye tissues and plasma. Complement activation products were markedly reduced in C3-/- and Cfb-/- mice challenged with LPS. Ocular complement levels were also elevated in mice treated systemically with TLR2 and -3 ligands, injured by IVT injection or corneal debridement, or even in normal aging. IVT administration of a complement FD neutralizing antibody in rabbits inhibited LPS-induced complement activation in the posterior segment of the eye, but not in the anterior segment of the eye or in plasma.

Conclusions

Systemic TLR stimulation and eye tissue injury induced time-dependent alternative complement pathway activation in the eye. Ocular complement levels were also gradually elevated during aging. An anti-FD antibody IVT potently inhibited LPS-induced complement activation in the posterior segment of the eye. This study provides insights into the dynamic profile of ocular complement activation, which is valuable for complement research in eye diseases and for developing complement therapeutics for AMD.

Nonclinical Safety Evaluation of scAAV8-RLBP1 for Treatment of RLBP1 Retinitis Pigmentosa

Retinitis pigmentosa is a form of retinal degeneration usually caused by genetic mutations affecting key functional proteins. We have previously demonstrated efficacy in a mouse model of RLBP1 deficiency with a self-complementary AAV8 vector carrying the gene for human RLBP1 under control of a short RLBP1 promoter (CPK850).¹ In this article, we describe the nonclinical safety profile of this construct as well as updated efficacy data in the intended clinical formulation. In Rlbp1^−/− mice dosed at a range of CPK850 levels, a minimum efficacious dose of 3 × 10⁷ vg in a volume of 1 μL was observed. For safety assessment in these and Rlbp1^+/+ mice, optical coherence tomography (OCT) and histopathological analysis indicated retinal thinning that appeared to be dose-dependent for both Rlbp1 genotypes, with no qualitative difference noted between Rlbp1^+/+ and Rlbp1^−/− mice. In a non-human primate study, RLBP1 mRNA expression was detected and dose dependent intraocular inflammation and retinal thinning were observed. Inflammation resolved slowly over time and did not appear to be exacerbated in the presence of anti-AAV8 antibodies. Biodistribution was evaluated in rats and satellite animals in the non-human primate study. The vector was largely detected in ocular tissues and low levels in the optic nerve, superior colliculus, and lateral geniculate nucleus, with limited distribution outside of these tissues. These data suggest that an initial subretinal dose of ∼3 × 10⁷ vg/μL CPK850 can safely be used in clinical trials.

Specific correlation between the major chromosome 10q26 haplotype conferring risk for age-related macular degeneration and the expression of HTRA1

PURPOSE

A region within chromosome 10q26 has a set of single nucleotide polymorphisms (SNPs) that define a haplotype that confers high risk for age-related macular degeneration (AMD). We used a bioinformatics approach to search for genes in this region that may be responsible for risk for AMD by assessing levels of gene expression in individuals carrying different haplotypes and by searching for open chromatin regions in the retinal pigment epithelium (RPE) that might include one or more of the SNPs.

METHODS

We surveyed the PubMed and the 1000 Genomes databases to find all common (minor allele frequency > 0.01) SNPs in 10q26 strongly associated with AMD. We used the HaploReg and LDlink databases to find sets of SNPs with alleles in linkage disequilibrium and used the Genotype-Tissue Expression (GTEx) database to search for correlations between genotypes at individual SNPs and the relative level of expression of the genes. We also accessed Encyclopedia of DNA Elements (ENCODE) to find segments of open chromatin in the region with the AMD-associated SNPs. Predicted transcription factor binding motifs were identified using HOMER, PROMO, and RegulomeDB software programs.

RESULTS

There are 34 polymorphisms within a 30-kb region that are in strong linkage disequilibrium (r2>0.8) with the reference SNP rs10490924 previously associated with risk for AMD. The expression of three genes in this region, PLEKHA1, ARMS2, and HTRA1 varies between people who have the low-AMD-risk haplotype compared with those with the high-AMD-risk haplotype. For PLEKHA1, 44 tissues have an expression pattern with the high-AMD-risk haplotype associated with low expression (rs10490924 effect size -0.43, p = 3.8 x 10-5 in ovary). With regard to ARMS2, the variation is most pronounced in testes: homozygotes with the high-AMD-risk haplotype express ARMS2 at lower levels than homozygotes with the low-AMD-risk haplotype; expression in heterozygotes falls in between (rs10490924 effect size -0.79, p = 7.5 x 10-24). For HTRA1, the expression pattern is the opposite; the high-AMD-risk haplotype has higher levels of expression in 27 tissues (rs10490924 effect size 0.40, p = 1.5 × 10-7 in testes). None of the other 22 genes within one megabase of rs10490924, or any gene in the entire genome, have mRNA expression levels that correlate with the high-AMD-risk haplotype. More than 100 other SNPs in the 10q26 region affect the expression of PLEKHA1 and ARMS2 but not that of HTRA1; none of these SNPs affects the risk for AMD according to published genome-wide association studies (GWASs). Two of the AMD-risk SNPs (rs36212732 and rs36212733) affect transcription factor binding sites in proximity to a DNase I hypersensitive region (i.e., a region of open chromatin) in RPE cells.

CONCLUSIONS

SNPs in chromosome 10q26 that influence the expression of only PLEKHA1 or ARMS2 are not associated with risk for AMD, while most SNPs that influence the expression of HTRA1 are associated with risk for AMD. Two of the AMD-risk SNPs affect transcription factor binding sites that may control expression of one of the linked genes in the RPE. These findings suggest that the variation in the risk for AMD associated with chromosome 10q26 is likely due to variation in HTRA1 expression. Modulating HTRA1 activity might be a potential therapy for AMD.

AAV-mediated RLBP1 gene therapy improves the rate of dark adaptation in Rlbp1 knockout mice

Recessive mutations in RLBP1 cause a form of retinitis pigmentosa in which the retina, before its degeneration leads to blindness, abnormally slowly recovers sensitivity after exposure to light. To develop a potential gene therapy for this condition, we tested multiple recombinant adeno-associated vectors (rAAVs) composed of different promoters, capsid serotypes, and genome conformations. We generated rAAVs in which sequences from the promoters of the human RLBP1, RPE65, or BEST1 genes drove the expression of a reporter gene (green fluorescent protein). A promoter derived from the RLBP1 gene mediated expression in the retinal pigment epithelium and Müller cells (the intended target cell types) at qualitatively higher levels than in other retinal cell types in wild-type mice and monkeys. With this promoter upstream of the coding sequence of the human RLBP1 gene, we compared the potencies of vectors with an AAV2 versus an AAV8 capsid in transducing mouse retinas, and we compared vectors with a self-complementary versus a single-stranded genome. The optimal vector (scAAV8-pRLBP1-hRLBP1) had serotype 8 capsid and a self-complementary genome. Subretinal injection of scAAV8-pRLBP1-hRLBP1 in Rlbp1 nullizygous mice improved the rate of dark adaptation based on scotopic (rod-plus-cone) and photopic (cone) electroretinograms (ERGs). The effect was still present after 1 year.

Reliability of the mouse model of choroidal neovascularization induced by laser photocoagulation

PURPOSE

We attempted to reproduce published studies that evaluated whether the following factors influence choroidal neovascularization (CNV) induced by laser photocoagulation in murine retinas: small interfering RNA (siRNA), cobra venom factor, complement factors C3 and C5, and complement receptor C5aR. In addition, we explored whether laser-induced CNV in mice was influenced by the vendor of origin of the animals.

METHODS

Reagents or genotypes reported by others to influence CNV in this model were assessed using our standard procedures. Retrospective analyses of control or placebo mice in many experiments were done to evaluate whether the CNV area induced by laser photocoagulation varied according to vendor.

RESULTS

Administration of the following agents did not have a substantial impact on the CNV induced by laser burns in mice: siRNA, low-molecular-weight inhibitor of the C5a receptor (PMX53), or cobra venom factor. Jackson Laboratory (JAX) mice lacking either C3 or C5 had increased neovascularization compared to non-littermate JAX wild-type controls. Taconic mice lacking C3 had reduced CNV compared to non-littermate Taconic wild-type control mice. A retrospective analysis of vehicle-treated wild-type C57BL/6 mice used as controls across 132 experiments conducted from 2007 to 2010 revealed that mice purchased from JAX or from Charles River produced less neovascularization than mice from Taconic.

CONCLUSIONS

We present our recommended methods for conducting experiments with the mouse laser-induced CNV model to enhance reproducibility and minimize investigator bias.

Intra-articular injection of tumor necrosis factor-alpha in the rat: an acute and reversible in vivo model of cartilage proteoglycan degradation

OBJECTIVE

To develop an in vivo model for rapid assessment of cartilage aggrecan degradation and its pharmacological modulation.

DESIGN

Tumor necrosis factor-alpha (TNFalpha) was injected intra-articularly (IA) in rat knees and aggrecan degradation was monitored at various times following challenge. Articular cartilage was assessed for aggrecan content by Safranin O staining and by immunohistochemistry for the NITEGE epitope. Synovial fluids (SFs) were analyzed for sulfated glycosaminoglycans (GAGs) using the dimethylmethylene blue dye assay and for aggrecan fragments generated by specific cleavage at aggrecanase-sensitive sites by Western blot analysis with neoepitope antibodies. Indomethacin, dexamethasone, and an aggrecanase inhibitor were evaluated for their ability to modulate TNFalpha-induced proteoglycan degradation in vivo.

RESULTS

(1) IA injection of TNFalpha in the knee joint of rats resulted in transient aggrecan degradation and release of aggrecanase-generated aggrecan fragments from the articular cartilage into the SF; (2) a correlation was observed between histologically assessed depletion of aggrecan from the articular cartilage and the appearance of specific neoepitopes in the SF; (3) aggrecan degradation was inhibited by an aggrecanase inhibitor as well as by dexamethasone, but not by the non-steroidal anti-inflammatory drug (NSAID), indomethacin.

CONCLUSION

TNFalpha injection in the knee joints of rats results in rapid transient cartilage proteoglycan degradation, mediated by cleavage at the aggrecanase sites. Biomarker read-out of specific neoepitopes in the SF enables the use of this mechanism-based model for rapid evaluation of aggrecanase-mediated aggrecan degradation in vivo.

A selective small molecule IkappaB Kinase beta inhibitor blocks nuclear factor kappaB-mediated inflammatory responses in human fibroblast-like synoviocytes, chondrocytes, and mast cells

IkappaB kinase (IKK) beta is essential for inflammatory cytokine-induced activation of nuclear factor kappaB (NF-kappaB). NF-kappaB plays a pivotal role in the function of major cell types that contribute to the pathophysiological process of rheumatoid arthritis (RA). Here, we report the mechanism and the effect of the IKKbeta inhibitor N-(6-chloro-7-methoxy-9H-beta-carbolin-8-yl)-2-methylnicotinamide (ML120B), a beta-carboline derivative, on NF-kappaB signaling and gene activation in RA-relevant cell systems. ML120B is a potent, selective, reversible, and ATP-competitive inhibitor of IKKbeta with an IC50 of 60 nM when evaluated in an IkappaBalpha kinase complex assay. ML120B does not inhibit other IKK isoforms or a panel of other kinases. ML120B concentration-dependently inhibits tumor necrosis factor alpha (TNFalpha)-stimulated NF-kappaB signaling via inhibition of IkappaBalpha phosphorylation, degradation, and NF-kappaB translocation into the nucleus. For the first time, we have demonstrated that in human fibroblast-like synoviocytes, TNFalpha- or interleukin (IL)-1beta-induced monocyte chemoattractant protein-1 regulated on activation, normal T cell expressed and secreted and production is IKKbeta-dependent. In addition, for the first time, we have demonstrated that lipopolysaccharide- or peptidoglycan-induced cytokine production in human cord blood-derived mast cells is IKKbeta-dependent. In addition, in human chondrocytes, ML120B inhibited IL-1beta-induced matrix metalloproteinase production with an IC50 of approximately 1 microM. ML120B also blocked IL-1beta-induced prostaglandin E2 production. In summary, ML120B blocked numerous NF-kappaB-regulated cell responses that are involved in inflammation and destructive processes in the RA joint. Our findings support the evaluation of IKKbeta inhibitors as anti-inflammatory agents for the treatment of RA.

Discovery of macrocyclic hydroxamic acids containing biphenylmethyl derivatives at P1', a series of selective TNF-alpha converting enzyme inhibitors with potent cellular activity in the inhibition of TNF-alpha release

SAR exploration at P1' using an anti-succinate-based macrocyclic hydroxamic acid as a template led to the identification of several bulky biphenylmethyl P1' derivatives which confer potent porcine TACE and anti-TNF-alpha cellular activities with high selectivity versus most of the MMPs screened. Our studies demonstrate for the first time that TACE has a larger S1' pocket in comparison to MMPs and that potent and selective TACE inhibitors can be achieved by incorporation of sterically bulky P1' residues.

Design, synthesis, and structure-activity relationships of macrocyclic hydroxamic acids that inhibit tumor necrosis factor alpha release in vitro and in vivo

To search for TNF-alpha (tumor necrosis factor alpha) converting enzyme (TACE) inhibitors, we designed a new class of macrocyclic hydroxamic acids by linking the P1 and P2' residues of acyclic anti-succinate-based hydroxamic acids. A variety of residues including amide, carbamate, alkyl, sulfonamido, Boc-amino, and amino were found to be suitable P1-P2' linkers. With an N-methylamide at P3', the 13-16-membered macrocycles prepared exhibited low micromolar activities in the inhibition of TNF-alpha release from LPS-stimulated human whole blood. Further elaboration in the P3'-P4' area using the cyclophane and cyclic carbamate templates led to the identification of a number of potent analogues with IC(50) values of </=0.2 microM in whole blood assay (WBA). Although the P3' area can accommodate a broad array of structurally diversified functional groups including polar residues, hydrophobic residues, and amino and carboxylic acid moieties, in both the cyclophane series and the cyclic carbamate series, a glycine residue at P3' was identified as a critical structural component to achieve both good in vitro potency and good oral activity. With a glycine residue at P3', an N-methylamide at P4' provided the best cyclophane analogue, SL422 (WBA IC(50) = 0.22 microM, LPS-mouse ED(50) = 15 mg/kg, po), whereas a morpholinylamide at P4' afforded the most potent and most orally active cyclic carbamate analogue, SP057 (WBA IC(50) = 0.067 microM, LPS-mouse ED(50) = 2.3 mg/kg, po). Further profiling for SL422 and SP057 showed that these macrocyclic compounds are potent TACE inhibitors, with K(i) values of 12 and 4.2 nM in the porcine TACE assay, and are broad-spectrum MMP inhibitors. Pharmacokinetic studies in beagle dogs revealed that SL422 and SP057 are orally bioavailable, with oral bioavailabilities of 11% and 23%, respectively.

Inhibition of MAP kinase kinase (MEK) results in an anti-inflammatory response in vivo

The MAP kinase pathway has been well-characterized as a cascade of sequential protein phosphorylation events leading to the upregulation of a variety of genes in response to growth factors and mitogens. We are interested in the role of these kinases in inflammation and have thus examined their activity in vivo using TPA-induced ear edema in the mouse as a model of inflammation. We show that the activities of both ERK-1 and ERK-2 are upregulated in this model in response to TPA. Increased levels of ERK phosphorylation are measurable as early as 15 min poststimulation and reach a level 8-fold over controls at 4 h. In contrast, minimal activation of JNK or p38 is observed. Topical treatment of ears with the MEK inhibitor, U0126, prevents ERK phosphorylation and ear swelling in a dose-dependent manner in this model. These results suggest that the MEK/ERK pathway is important during an inflammatory response in vivo.

Macrocyclic hydroxamate inhibitors of matrix metalloproteinases and TNF-alpha production

Several macrocyclic, hydroxamate derivatives were synthesized and evaluated as inhibitors of matrix metalloproteinases (MMPs) and tumour necrosis factor-alpha (TNF-alpha) production. These macrocycles are anti-succinate based inhibitors linked from P1 to P2'. A variety of functionality was installed at the P1-P2' linkage, which gave inhibitors that displayed excellent MMP inhibition and good TNF-alpha suppression.

Heteroatom- and carbon-linked biphenyl analogs of Brequinar as immunosuppressive agents

Structure-activity relationships were explored for some analogs of Brequinar having a linking atom between the 2-biphenyl substituent and the quinoline ring. Activities as inhibitors of dihydroorotate dehydrogenase and the mixed lymphocyte reaction were related to the overall shape and lipophilicity of the 2-substituent.

Inhibition of Mitogen-Activated Protein Kinase Kinase Blocks T Cell Proliferation But Does Not Induce or Prevent Anergy

Three mitogen-activated protein kinase pathways are up-regulated during the activation of T lymphocytes, the extracellular signal-regulated kinase (ERK), Jun NH2-terminal kinase, and p38 mitogen-activated protein kinase pathways. To examine the effects of blocking the ERK pathway on T cell activation, we used the inhibitor U0126, which has been shown to specifically block mitogen-activated protein kinase/ERK kinase (MEK), the kinase upstream of ERK. This compound inhibited T cell proliferation in response to antigenic stimulation or cross-linked anti-CD3 plus anti-CD28 Abs, but had no effect on IL-2-induced proliferation. The block in T cell proliferation was mediated by down-regulating IL-2 mRNA levels. Blocking Ag-induced proliferation by inhibiting MEK did not induce anergy, unlike treatments that block entry into the cell cycle following antigenic stimulation. Surprisingly, induction of anergy in T cells exposed to TCR cross-linking in the absence of costimulation was also not affected by blocking MEK, unlike cyclosporin A treatment that blocks anergy induction. These results suggest that inhibition of MEK prevents T cell proliferation in the short term, but does not cause any long-term effects on either T cell activation or induction of anergy. These findings may help determine the viability of using mitogen-activated protein kinase inhibitors as immune suppressants.

Inhibition of mitogen-activated protein kinase kinase blocks T cell proliferation but does not induce or prevent anergy

Three mitogen-activated protein kinase pathways are up-regulated during the activation of T lymphocytes, the extracellular signal-regulated kinase (ERK), Jun NH2-terminal kinase, and p38 mitogen-activated protein kinase pathways. To examine the effects of blocking the ERK pathway on T cell activation, we used the inhibitor U0126, which has been shown to specifically block mitogen-activated protein kinase/ERK kinase (MEK), the kinase upstream of ERK. This compound inhibited T cell proliferation in response to antigenic stimulation or cross-linked anti-CD3 plus anti-CD28 Abs, but had no effect on IL-2-induced proliferation. The block in T cell proliferation was mediated by down-regulating IL-2 mRNA levels. Blocking Ag-induced proliferation by inhibiting MEK did not induce anergy, unlike treatments that block entry into the cell cycle following antigenic stimulation. Surprisingly, induction of anergy in T cells exposed to TCR cross-linking in the absence of costimulation was also not affected by blocking MEK, unlike cyclosporin A treatment that blocks anergy induction. These results suggest that inhibition of MEK prevents T cell proliferation in the short term, but does not cause any long-term effects on either T cell activation or induction of anergy. These findings may help determine the viability of using mitogen-activated protein kinase inhibitors as immune suppressants.

Structure-activity relationships (SAR) of some tetracyclic heterocycles related to the immunosuppressive agent Brequinar Sodium

The structure-activity relationships of some tetracyclic heterocycles related to Brequinar were explored. Activities as inhibitors of dihydroorotate dehydrogenase and the mixed lymphocyte reaction are related to ring system, heteroatom placement, and pendant ring substitution.

Renal abnormalities and an altered inflammatory response in mice lacking cyclooxygenase II

Prostaglandins have wide-ranging effects in the body and are thought to be important mediators of inflammation. Cyclooxygenase (COX) plays a key regulatory role in prostaglandin synthesis, and occurs in both constitutive (COX-1) and inducible (COX-2) isoforms. COX-1 is thought to provide cytoprotective effects, whereas COX-2 is both inducible and the major isoform of inflammatory cells. Reduction of prostaglandin production by inhibition of cyclooxygenases appears to be the main mechanism of action of most non-steroidal anti-inflammatory drugs (NSAIDS). Here we present an animal model of COX-2 deficiency that was generated by gene targeting. Defects in null mice correlating with reduced viability included renal alterations, characteristic of renal dysplasia (100% penetrance), and cardiac fibrosis (50% penetrance). Female Cox-2-/- mice were infertile. COX-2 deficiency failed to alter inflammatory responses in several standard models, but striking mitigation of endotoxin-induced hepatocellular cytotoxicity was observed.

Novel mechanisms of brequinar sodium immunosuppression on T cell activation

Brequinar sodium (BQR) is a novel immunosuppressive agent that acts by inhibiting the activity of dihydroorotate dehydrogenase, the fourth enzyme in the de novo pyrimidine biosynthetic pathway. The activity of BQR as an immunosuppressive agent is believed to be inhibition of antigen-induced lymphocyte proliferation through inhibition of DNA and RNA synthesis. BQR, therefore, has a different mechanism of action than cyclosporine and may potentiate the immunosuppressive effects of cyclosporine. In this study, we determined the effect of BQR on peripheral blood mononuclear cell (PBMC) activation in a series of in vitro culture systems. In these studies, BQR inhibited PHA-stimulated activation in a dose-dependent fashion beginning at 10(-6) M. The immunosuppressive effect of BQR was similar in magnitude to cyclosporine. Proliferation assays suggested an additive immunosuppression by the combination of BQR and cyclosporine. Similar inhibition of CD2-stimulated or CD3-stimulated activation of PBMC was found. The mechanisms of action of BQR were complex. BQR inhibited interleukin 2 protein production in response to mitogen stimulation. Cell surface interleukin 2 receptor expression was inhibited by BQR. BQR inhibited cell cycle progression, preventing progression from G0/G1 into S and G2 + M phases. BQR had no effect on induction of transcripts for the interleukin 2 receptor, but markedly inhibited the production of transcripts for interleukin 2. Thus, our studies indicate that BQR exerts a potent immunosuppression on mitogen-induced PBMC activation through multiple mechanisms. Consequently, BQR may be an effective agent for immunosuppression in organ transplantation or inflammatory diseases.

The prolongation of concordant hamster-to-rat cardiac xenografts by brequinar sodium

Brequinar sodium (BQR) prevents cell proliferation by virtue of its inhibition of de novo pyrimidine biosynthesis. The immunosuppressive activity of BQR is highly effective in prolonging heart, liver, and kidney allograft survival in the rat. In these experiments, we have tested the ability of BQR to prevent the rejection of concordant cardiac xenografts. LEW inbred rats transplanted with heterotopic hamster hearts were treated orally with brequinar sodium as a single agent. The survival of the cardiac xenografts was significantly prolonged with a variety of treatment regimens. The most effective treatment was the daily oral administration of BQR at 3 mg/kg. At this level, the median graft survival was approximately 25 days. Four animals had hamster heart xenografts that functioned for more than 90 days. The prolonged survival of the xenografts was associated with relatively constant plasma drug levels of approximately 1 to 3 micrograms/ml and a marked suppression of IgM production. At rejection, there was a significant rise in IgM levels compared with those of recipients with stable xenografts. In vitro MLR responses were effectively inhibited by BQR, with an IC50 of 0.08 microgram/ml. The results of these experiments demonstrate that BQR is a new immunosuppressive agent that is highly effective as a single agent in prolonging the survival of hamster-to-rat cardiac xenografts. The prolonged xenograft survival is associated with effective suppression of rat antihamster antibody production, suggesting that brequinar sodium may be an important addition to multidrug immunosuppressive regimes designed to prevent B and T lymphocyte-mediated immune responses.

Therapy of chronic relapsing experimental allergic encephalomyelitis and the role of the blood-brain barrier: elucidation by the action of Brequinar sodium

The immunosuppressive effect of the novel 4-quinoline carboxylic acid derivative Brequinar sodium on the chronic relapsing experimental allergic encephalomyelitis CREAE model in the Biozzi AB/H mouse was investigated. Although Brequinar sodium actively inhibited peripheral immune responses, it showed a limited potential to control an ongoing disease of the central nervous system (CNS). Doses of 25 mg/kg inhibited in vivo induced proliferative response and prevented EAE when treated from day 9 post-inoculation (p.i.). However, when administered from day 12 p.i. or during the post-acute remission phase-limited effects on the course of disease were observed. By comparison, treatment with a single high dose of cyclophosphamide (200 mg/kg) at these time points was significantly effective in controlling disease. As a possible explanation of the observed results it is suggested that for a compound to be effective in treating an ongoing immune response in the CNS, it must be capable of crossing the blood-brain barrier and act on the disease-inducing cells activated within the CNS. This hypothesis is supported by the finding that intracerebral injections of Brequinar sodium on day 12 p.i. significantly inhibited disease progression. This suggests that strategies aimed at controlling immune-mediated disease of the CNS require therapeutic doses of the compounds to be delivered into the CNS.

The effect of a new immunosuppressive drug, brequinar sodium, on heart, liver, and kidney allograft rejection in the rat

Brequinar sodium (BQR) prevents cell proliferation by virtue of its inhibition of de novo pyrimidine biosynthesis. BQR is capable of inhibiting immune responses in vitro and is effective in suppressing the development of contact sensitivity and adjuvant arthritis in rodent models. Based on the antiproliferative and immunosuppressive capacity of BQR, we have evaluated the efficacy of BQR in preventing allograft rejection utilizing experimental models of heterotopic heart and kidney and orthotopic liver transplantation in an MHC and non-MHC mismatched ACI----LEW rat strain combination. The immunosuppressive activity of BQR is illustrated by its ability to inhibit the development of delayed-type hypersensitivity to DNFB in mice. When BQR was administered orally throughout the sensitization and elicitation phases of the DNFB contact sensitivity response, it was found to be a potent immunosuppressant with an ED50 value of 0.5 mg/kg. This immunosuppressive activity is also seen in vitro, where BQR is capable of inhibiting the mixed lymphocyte response between allogeneic ACI and LEW rat strains with an IC50 of 150 ng/ml. The immunosuppressive activity of BQR is highly effective in prolonging heart, liver, and kidney allograft survival in the rat. Cardiac allografts are not rejected during the period of drug treatment at dosage levels of 12 to 24 mg/kg orally three times weekly. The grafts survive until the drug is discontinued (30 days posttransplantation), and the grafts are then rejected approximately 14 days later. Liver and kidney allografts are permanently accepted by approximately 50 to 90% of the recipient rats following 30 days of treatment with BQR at 12 mg/kg. The tolerance that is induced to the liver grafts extends in the majority of animals to greater than 250 days and is specific for the donor ACI strain. Challenge of long-term liver graft survivors with donor cardiac grafts is associated with permanent survival of donor, but not third-party, heart grafts. Combination therapy consisting of suboptimal doses of BQR and CsA demonstrates that the combination of these two immunosuppressive drugs results in an increased efficacy in prolonging graft survival. The results of these allograft experiments demonstrate that this new immunosuppressive agent is highly effective in preventing allograft rejection in the rat. The antiproliferative activity of BQR is effective for inhibiting T-lymphocyte-mediated immune responses, and Brequinar sodium should be an important addition to a polytherapeutic approach in the treatment of organ graft rejection.

The effect of immunomodulating drugs on adjuvant-induced arthritis in Lewis rats

The purpose of this study was to investigate the effects of cyclosporine A (CSA) and methotrexate (MTX) as potential immunomodulators in a nonestablished adjuvant arthritis (AA) model. Non-injected hind paw volumes were reduced when AA rats were treated for 18 days with CSA (100% at 10 mg/kg) or MTX (100% at 0.1 mg/kg). Body weights of drug treated AA rats were increased above untreated AA rats and were similar to non-arthritic controls. AA rats show elevated T helper (W3/25+)/T suppressor (OX 8+) cell ratios (2.0 vs. 3.1, p less than 0.01). The immunomodulators tested all returned these elevated ratios to control non-arthritic levels. Similarly, these drugs returned the reduced mitogen responses and elevated blood granulocyte numbers toward normal non-arthritic control values.

Chronic graft-versus-host disease as a model for scleroderma. II. Mast cell depletion with deposition of immunoglobulins in the skin and fibrosis

We explored the pathologic changes in the skin of mice undergoing a chronic graft-versus-host (GVH) reaction. In rodents and in man, chronic GVH includes the deposition of excess collagen in the skin-a reaction which resembles idiopathic scleroderma. GVH disease across minor histocompatibility barriers was produced by injecting B10.D2 cells into irradiated BALB/c mice. These strains are identical at the H-2 and Mls loci but differ in minor histocompatibility antigens. Control BALB/c mice received irradiation and BALB/c cells. Serial skin biopsies were taken and studied for histological changes characteristic of chronic GVHD, for mast cell density, and for the deposition of immunoreactants. GVHD was produced in B10.D2----BALB/c mice as measured by body weight loss and the production of skin changes including dermal fibrosis, loss of fat and appendages, and a mononuclear cell infiltrate. Dermal mast cells, assessed by toluidine blue staining, were normal at Day 11, but had disappeared by Days 21-63 and returned to normal by Day 104. Immunoglobulins IgG, IgA, and IgM appeared at the dermo-epidermal junction and along the basement membrane zone of hair follicles. This deposition was maximal at Day 42 and waned thereafter. Thus the appearance of immunoglobulins in the skin was maximal when mast cell staining was minimal. The changes in this GVHD model leading to a scleroderma-like picture in the skin are compatible with an immune etiology for the fibrosis. Vasodilation following liberation of mast cell mediators would facilitate the deposition of immunoglobulins. The disappearance of mast cell staining may be caused by extensive degranulation. We postulate an interaction between GVHD-activated T cells, mast cell stimulation, fibroblast activation, and fibrosis.

Minor antigen graft-versus-host reactions revealed in irradiated spleen and popliteal lymph node assays

The graft-versus-hot (GVH) reaction across minor (non-H-2) histocompatibility barriers was studied in mice, in vivo. To increase GVH potential and to mimic clinical bone marrow transplantation protocols, we modified the popliteal lymph node (PLN) and the splenomegaly assays by irradiating the recipients before they received allogeneic lymphoid cell suspensions. In several combinations across major (H-2), minor (non-H-2) and multiple minor (non-H-2 plus minor lymphocyte stimulation) barriers, increased recipient organ weight (a measure of GVH activity) was seen with irradiated F1 recipients of parental cells. The irradiated splenomegaly (x-splenomegaly) assay was more sensitive than the (x-PLN) assay, but both correlated with in vivo GVH experiments of the P----F1 variety. The x-splenomegaly test indicated histoincompatibility in a system (B10.D2----BALB/c) in which the primary in vitro mixed leukocyte reactions is nonreactive, but in which systemic GVH can be induced. The x-splenomegaly test should be useful in analyzing complex reactions involving minor histocompatibility antigens in vivo.

Desensitization of contact allergy to DNFB in mice. I. Description of a model system

We investigated the down-regulation of contact sensitivity (desensitization) in mice sensitized to DNFB. Mice were sensitized with DNFB, desensitized with antigen 2 wk later, and resensitized 2 wk after desensitization. Large doses of antigen (DNFB or DNBSO3) produced about 50% inhibition of the anamnestic response as measured by ear swelling after challenge with DNFB. Desensitization was antigen specific and long lasting. Lymph node cells from desensitized mice showed diminished antigen-induced proliferation in vitro. Although the anamnestic response can be inhibited by afferent- or efferent-acting suppressor cells, such suppressor cells were not demonstrated in desensitized animals. The most likely explanation is that antigen desensitizes by inactivating effector cells for contact sensitivity, although suppressor mechanisms have not been completely excluded.

Desensitization of contact allergy to DNFB in mice. I. Description of a model system

We investigated the down-regulation of contact sensitivity (desensitization) in mice sensitized to DNFB. Mice were sensitized with DNFB, desensitized with antigen 2 wk later, and resensitized 2 wk after desensitization. Large doses of antigen (DNFB or DNBSO3) produced about 50% inhibition of the anamnestic response as measured by ear swelling after challenge with DNFB. Desensitization was antigen specific and long lasting. Lymph node cells from desensitized mice showed diminished antigen-induced proliferation in vitro. Although the anamnestic response can be inhibited by afferent- or efferent-acting suppressor cells, such suppressor cells were not demonstrated in desensitized animals. The most likely explanation is that antigen desensitizes by inactivating effector cells for contact sensitivity, although suppressor mechanisms have not been completely excluded.

Chronic graft-versus-host disease (GVHD) as a model for scleroderma. I. Description of model systems

A model murine system of chronic graft-versus-host disease (GVHD) was explored to determine its suitability for studying scleroderma-like syndromes. The basic protocol was to inject lymphoid cell suspensions into irradiated semiallogeneic or allogeneic recipients which had been irradiated. Serial body weights, skin biopsies, and anti-nuclear antibodies were followed. Changes seen in the skin included increased collagen deposition, a mononuclear infiltrate deep in the dermis, loss of dermal fat, and "dropout" of skin appendages such as hair follicles. Body weight loss was a sensitive index of GVHD. Anti-nuclear antibodies occurred at times, but did not correlate with the tissue changes in the skin of mice undergoing GVHD. This chronic GVHD syndrome was produced across major and minor histocompatibility barriers. The most consistent findings were seen in BALB/c recipients of B10.D2 cells. These strains are nonreactive in unprimed mixed-leukocyte cultures. This combination represents primarily a GVH reaction against minor antigens where the HVG reaction is suppressed by irradiation. Some data suggest that the cutaneous changes may be reversible with time.

Regional lymph node x-radiation suppresses allograft rejection

We studied the effect of a single dose of x-radiation given to the regional lymph nodes on allograft rejection. Our model was an A-strain tumor, transplanted to C57B1/6, DBA/2, and C57B1/6 x CBA hosts. Irradiation (1,000 rad) of the regional lymph nodes inhibited graft rejection, as judged by increased tumor growth, slower rejection, and, in the case of DBA/2 mice, by fewer regressions; irradiation of the contralateral lymph nodes did not have this effect. The mechanism of immunosuppression appeared to be B-cell independent, since immunosuppression could be induced by regional x-radiation as readily in B-cell deficient mice as in normal mice. The suppression was critically time-dependent, viz, irradiation before, or 6 or more days after, tumor graft was without significant effect. Treatment of the allogeneic host with cyclophosphamide several days before grafting, so as to reduce T-suppressor cells, attenuated the immunosuppression of regional x-radiation.