From the Lab to the Clinic: Activation of an Alpha-2 agonist Pathway is Neuroprotective in Models of Retinal and Optic Nerve Injury

PURPOSE

The selective alpha-2 agonist brimonidine was used as a pharmacological probe to activate alpha 2 receptor-mediated neuroprotective signaling pathways and quantitate the enhancement of retinal ganglion cell survival and function in animals with ischemic retinal and optic nerve injury.

METHODS

Two animal models were used to achieve different methods of neuronal insult. The first model involved mechanical injury of the rat optic nerve after treatment with a single intraperitoneal (i.p.) dose of brimonidine or a control vehicle. The second model involving acute retinal ischemic/reperfusion injury was used in a variety of experiments in which rats were treated with either intraperitoneal brimonidine or single dose topical brimonidine at various strengths. In all cases retinal ischemia was induced and maintained followed by reperfusion. In some cases, TUNEL staining was performed on histologic sections of the retinas of rats that had been sacrificed after 24 hours. To examine the activation of neuronal survival pathways at the molecular level, rats were injected with i.p. brimonidine followed by the isolation of mRNAs from whole retinas 24 hours after ischemic injury.

RESULTS

Intraperitoneal brimonidine enhanced rat RGC survival and function in the partial crush injury model, and neuroprotection was dose-dependent. Topical application of brimonidine 1 hour before injury was effective in decreasing ischemic retinal injury. Ischemic retinas treated with brimonidine resulted with a large decrease in TUNEL staining.

CONCLUSIONS

Treatment with the alpha 2 adrenoreceptor agonist brimonidine was found to confer neuroprotection to retinal ganglion cells in two distinct models of neuronal injury resulting from acute retinal ischemia/reperfusion and calibrated optic nerve compression.

BMPR2 mutations and survival in pulmonary arterial hypertension: an individual participant data meta-analysis

BACKGROUND

Mutations in the gene encoding the bone morphogenetic protein receptor type II (BMPR2) are the commonest genetic cause of pulmonary arterial hypertension (PAH). However, the effect of BMPR2 mutations on clinical phenotype and outcomes remains uncertain.

METHODS

We analysed individual participant data of 1550 patients with idiopathic, heritable, and anorexigen-associated PAH from eight cohorts that had been systematically tested for BMPR2 mutations. The primary outcome was the composite of death or lung transplantation. All-cause mortality was the secondary outcome. Hazard ratios (HRs) for death or transplantation and all-cause mortality associated with the presence of BMPR2 mutation were calculated using Cox proportional hazards models stratified by cohort.

FINDINGS

Overall, 448 (29%) of 1550 patients had a BMPR2 mutation. Mutation carriers were younger at diagnosis (mean age 35·4 [SD 14·8] vs 42·0 [17·8] years), had a higher mean pulmonary artery pressure (60·5 [13·8] vs 56·4 [15·3] mm Hg) and pulmonary vascular resistance (16·6 [8·3] vs 12·9 [8·3] Wood units), and lower cardiac index (2·11 [0·69] vs 2·51 [0·92] L/min per m(2); all p<0·0001). Patients with BMPR2 mutations were less likely to respond to acute vasodilator testing (3% [10 of 380] vs 16% [147 of 907]; p<0·0001). Among the 1164 individuals with available survival data, age-adjusted and sex-adjusted HRs comparing BMPR2 mutation carriers with non-carriers were 1·42 (95% CI 1·15-1·75; p=0·0011) for the composite of death or lung transplantation and 1·27 (1·00-1·60; p=0·046) for all-cause mortality. These HRs were attenuated after adjustment for potential mediators including pulmonary vascular resistance, cardiac index, and vasoreactivity. HRs for death or transplantation and all-cause mortality associated with BMPR2 mutation were similar in men and women, but higher in patients with a younger age at diagnosis (p=0·0030 for death or transplantation, p=0·011 for all-cause mortality).

INTERPRETATION

Patients with PAH and BMPR2 mutations present at a younger age with more severe disease, and are at increased risk of death, and death or transplantation, compared with those without BMPR2 mutations.

FUNDING

Cambridge NIHR Biomedical Research Centre, Medical Research Council, British Heart Foundation, Assistance Publique-Hôpitaux de Paris, INSERM, Université Paris-Sud, Intermountain Research and Medical Foundation, Vanderbilt University, National Center for Advancing Translational Sciences, National Institutes of Health, National Natural Science Foundation of China, and Beijing Natural Science Foundation.

Estrogen Metabolite 16α-Hydroxyestrone Exacerbates Bone Morphogenetic Protein Receptor Type II-Associated Pulmonary Arterial Hypertension Through MicroRNA-29-Mediated Modulation of Cellular Metabolism

BACKGROUND

Pulmonary arterial hypertension (PAH) is a proliferative disease of the pulmonary vasculature that preferentially affects women. Estrogens such as the metabolite 16α-hydroxyestrone (16αOHE) may contribute to PAH pathogenesis, and alterations in cellular energy metabolism associate with PAH. We hypothesized that 16αOHE promotes heritable PAH (HPAH) via microRNA-29 (miR-29) family upregulation and that antagonism of miR-29 would attenuate pulmonary hypertension in transgenic mouse models of Bmpr2 mutation.

METHODS AND RESULTS

MicroRNA array profiling of human lung tissue found elevation of microRNAs associated with energy metabolism, including the miR-29 family, among HPAH patients. miR-29 expression was 2-fold higher in Bmpr2 mutant mice lungs at baseline compared with controls and 4 to 8-fold higher in Bmpr2 mice exposed to 16αOHE 1.25 μg/h for 4 weeks. Blot analyses of Bmpr2 mouse lung protein showed significant reductions in peroxisome proliferator-activated receptor-γ and CD36 in those mice exposed to 16αOHE and protein derived from HPAH lungs compared with controls. Bmpr2 mice treated with anti-miR-29 (20-mg/kg injections for 6 weeks) had improvements in hemodynamic profile, histology, and markers of dysregulated energy metabolism compared with controls. Pulmonary artery smooth muscle cells derived from Bmpr2 murine lungs demonstrated mitochondrial abnormalities, which improved with anti-miR-29 transfection in vitro; endothelial-like cells derived from HPAH patient induced pluripotent stem cell lines were similar and improved with anti-miR-29 treatment.

CONCLUSIONS

16αOHE promotes the development of HPAH via upregulation of miR-29, which alters molecular and functional indexes of energy metabolism. Antagonism of miR-29 improves in vivo and in vitro features of HPAH and reveals a possible novel therapeutic target.

Elevation of plasma cell-free hemoglobin in pulmonary arterial hypertension

BACKGROUND

Cell-free hemoglobin (CFH) is a potent nitric oxide scavenger associated with poor outcomes in several diseases. Pulmonary arterial hypertension (PAH) is characterized by reduced nitric oxide availability. We hypothesized that CFH would be elevated in PAH and would associate with hemodynamics and clinical outcomes.

METHODS

We measured CFH in 200 consecutively evaluated patients with PAH, 16 unaffected bone morphogenetic receptor protein type 2 (BMPR2) mutation carriers, 19 healthy subjects, and 29 patients with pulmonary venous hypertension (PVH). CFH values were tested for association with hemodynamics, time to hospitalization, and death.

RESULTS

CFH was elevated in patients with PAH and BMPR2 carriers compared with healthy subjects and patients with PVH (P ≤ .01 all comparisons). There were no differences in CFH across PAH subtypes. CFH modestly correlated with mean pulmonary artery pressure (ρ = 0.16, P = .03) and pulmonary vascular resistance (ρ = 0.21, P = .01) and inversely with cardiac index (ρ = -0.18, P = .02) in patients with PAH. CFH was not associated with hemodynamic response to nitric oxide or death. Patients with the highest CFH levels had increased risk of PAH-related hospitalization when adjusted for age, sex, and PAH cause (hazard ratio, 1.69; 95% CI ,1.08-2.66; P = .02).

CONCLUSIONS

CFH is elevated in patients with PAH and BMPR2 carriers compared with healthy subjects and patients with PVH. Elevated CFH levels are independently associated with an increased risk of hospitalization. Further study is required to understand the mechanism of CFH elevation and the potential pathologic contribution of CFH in PAH.

Prostanoids but not oral therapies improve right ventricular function in pulmonary arterial hypertension

OBJECTIVES

This study hypothesized that right ventricular stroke work index (RVSWI) and pulmonary capacitance (PC) would increase after treatment for pulmonary arterial hypertension (PAH) and that prostanoids would have a stronger effect than oral therapy.

BACKGROUND

Right ventricular (RV) function is a major determinant of outcome in patients with PAH. Little is known about the response of RV function or its hemodynamic determinants to PAH-specific therapy.

METHODS

We reviewed hemodynamic and health data on 58 patients from an institutional registry and analyzed changes in hemodynamic status between diagnostic and first repeat catheterization after initiation of therapy for PAH.

RESULTS

The RVSWI and PC increased significantly after therapy (p = 0.007 and p = 0.02, respectively). Improvement in RV function was limited to patients treated with prostanoid-only therapy (p = 0.04); no improvement was found in patients treated with oral therapy (p = 0.25). Patients with the poorest baseline RV function (lowest tertile) had the greatest improvement post-therapy (p = 0.005 and p < 0.001 vs. middle and highest tertiles). The major determinant of RVSWI was change in stroke volume (r(s) = 0.54, p < 0.001), indicating RVSWI is an accurate reflection of RV function.

CONCLUSIONS

Right ventricular function improves after therapy with regimens including prostanoids but not oral-only regimens. Patients with the least compensated RV function at diagnosis might derive the most benefit from therapy. Larger studies are needed to determine whether changes in RVSWI after therapy are associated with outcomes.

Inhibition of cyclophilin D by cyclosporin A promotes retinal ganglion cell survival by preventing mitochondrial alteration in ischemic injury

Cyclosporin A (CsA) inhibits the opening of the mitochondrial permeability transition pore (MPTP) by interacting with cyclophilin D (CypD) and ameliorates neuronal cell death in the central nervous system against ischemic injury. However, the molecular mechanisms underlying CypD/MPTP opening-mediated cell death in ischemic retinal injury induced by acute intraocular pressure (IOP) elevation remain unknown. We observed the first direct evidence that acute IOP elevation significantly upregulated CypD protein expression in ischemic retina at 12 h. However, CsA prevented the upregulation of CypD protein expression and promoted retinal ganglion cell (RGC) survival against ischemic injury. Moreover, CsA blocked apoptotic cell death by decreasing cleaved caspase-3 protein expression in ischemic retina. Of interest, although the expression level of Bcl-xL protein did not show a significant change in ischemic retina treated with vehicle or CsA at 12 h, ischemic damage induced the reduction of Bcl-xL immunoreactivity in RGCs. More importantly, CsA preserved Bcl-xL immunoreactivity in RGCs of ischemic retina. In parallel, acute IOP elevation significantly increased phosphorylated Bad (pBad) at Ser112 protein expression in ischemic retina at 12 h. However, CsA significantly preserved pBad protein expression in ischemic retina. Finally, acute IOP elevation significantly increased mitochondrial transcription factor A (Tfam) protein expression in ischemic retina at 12 h. However, CsA significantly preserved Tfam protein expression in ischemic retina. Studies on mitochondrial DNA (mtDNA) content in ischemic retina showed that there were no statistically significant differences in mtDNA content among control and ischemic groups treated with vehicle or CsA. Therefore, these results provide evidence that the activation of CypD-mediated MPTP opening is associated with the apoptotic pathway and the mitochondrial alteration in RGC death of ischemic retinal injury. On the basis of these observations, our findings suggest that CsA-mediated CypD inhibition may provide a promising therapeutic potential for protecting RGCs against ischemic injury-mediated mitochondrial dysfunction.

Shorter survival in familial versus idiopathic pulmonary arterial hypertension is associated with hemodynamic markers of impaired right ventricular function

Abstract Although individuals with familial pulmonary arterial hypertension (FPAH) have more severe hemodynamics, compared to individuals with idiopathic PAH (IPAH), it is unclear whether this translates into a survival difference. The influence of right ventricular (RV) function on survival in these groups is also unknown. We reviewed hemodynamic data and health information from a prospective institutional database of 57 FPAH and 66 IPAH patients registered with the Vanderbilt Pulmonary Hypertension Research Cohort. We compared hemodynamics at the time of diagnosis between the two groups and calculated pulmonary arteriolar capacitance (PC) and RV stroke work index (RVSWI). Using survival analysis, we compared freedom from a 5-year composite of death or lung transplantation in FPAH and IPAH patients. The composite outcome of death or transplant at 5 years from diagnosis was significantly increased in FPAH (log rank [Formula: see text]). PC and RVSWI were significantly decreased in FPAH, compared to IPAH ([Formula: see text] for both). In univariate analysis, PC (odds ratio [OR]: 0.17 [95% confidence interval (95% CI): 0.03-0.83]) and RVSWI (OR: 0.86 [95% CI: 0.77-0.95]) were predictors of mortality, as were cardiac index (OR: 0.17 [95% CI: 0.06-0.51]) and PVR (OR: 1.1 [95% CI: 1.01-1.12]). Among FPAH patients, RVSWI was lower in those who died or received a transplant than in survivors ([Formula: see text]), while PC was not ([Formula: see text]). We found significantly worse event-free survival and significantly lower PC and RVSWI in FPAH than in IPAH. In FPAH patients who died or underwent transplantation, RVSWI was lower than that in survivors, suggesting disproportionate RV dysfunction.

Loss-of-function thrombospondin-1 mutations in familial pulmonary hypertension

Most patients with familial pulmonary arterial hypertension (FPAH) carry mutations in the bone morphogenic protein receptor 2 gene (BMPR2). Yet carriers have only a 20% risk of disease, suggesting that other factors influence penetrance. Thrombospondin-1 (TSP1) regulates activation of TGF-β and inhibits endothelial and smooth muscle cell proliferation, pathways coincidentally altered in pulmonary arterial hypertension (PAH). To determine whether a subset of FPAH patients also have mutations in the TSP1 gene (THBS1) we resequenced the type I repeats of THBS1 encoding the TGF-β regulation and cell growth inhibition domains in 60 FPAH probands, 70 nonfamilial PAH subjects, and in large control groups. We identified THBS1 mutations in three families: a novel missense mutation in two (Asp362Asn), and an intronic mutation in a third (IVS8+255 G/A). Neither mutation was detected in population controls. Mutant 362Asn TSP1 had less than half of the ability of wild-type TSP1 to activate TGF-β. Mutant 362Asn TSP1 also lost the ability to inhibit growth of pulmonary arterial smooth muscle cells and was over threefold less effective at inhibiting endothelial cell growth. The IVS8+255 G/A mutation decreased and/or eliminated local binding of the transcription factors SP1 and MAZ but did not affect RNA splicing. These novel mutations implicate THBS1 as a modifier gene in FPAH. These THBS1 mutations have implications in the genetic evaluation of FPAH patients. However, since FPAH is rare, these data are most relevant as evidence for the importance of TSP1 in pulmonary vascular homeostasis. Further examination of THBS1 in the pathogenesis of PAH is warranted.

Truncating and missense BMPR2 mutations differentially affect the severity of heritable pulmonary arterial hypertension

BACKGROUND

Autosomal dominant inheritance of germline mutations in the bone morphogenetic protein receptor type 2 (BMPR2) gene are a major risk factor for pulmonary arterial hypertension (PAH). While previous studies demonstrated a difference in severity between BMPR2 mutation carriers and noncarriers, it is likely disease severity is not equal among BMPR2 mutations. We hypothesized that patients with missense BMPR2 mutations have more severe disease than those with truncating mutations.

METHODS

Testing for BMPR2 mutations was performed in 169 patients with PAH (125 with a family history of PAH and 44 with sporadic disease). Of the 106 patients with a detectable BMPR2 mutation, lymphocytes were available in 96 to functionally assess the nonsense-mediated decay pathway of RNA surveillance. Phenotypic characteristics were compared between BMPR2 mutation carriers and noncarriers, as well as between those carriers with a missense versus truncating mutation.

RESULTS

While there was a statistically significant difference in age at diagnosis between carriers and noncarriers, subgroup analysis revealed this to be the case only for females. Among carriers, there was no difference in age at diagnosis, death, or survival according to exonic location of the BMPR2 mutation. However, patients with missense mutations had statistically significant younger ages at diagnosis and death, as well as shorter survival from diagnosis to death or lung transplantation than those with truncating mutations. Consistent with this data, the majority of missense mutations were penetrant prior to age 36 years, while the majority of truncating mutations were penetrant after age 36 years.

CONCLUSION

In this cohort, BMPR2 mutation carriers have more severe PAH disease than noncarriers, but this is only the case for females. Among carriers, patients with missense mutations that escape nonsense-mediated decay have more severe disease than those with truncating mutations. These findings suggest that treatment and prevention strategies directed specifically at BMPR2 pathway defects may need to vary according to the type of mutation.

Alterations in oestrogen metabolism: implications for higher penetrance of familial pulmonary arterial hypertension in females

Mutations in bone morphogenetic protein receptor type 2 (BMPR2) cause familial pulmonary arterial hypertension (FPAH), but the penetrance is reduced and females are significantly overrepresented. In addition, gene expression data implicating the oestrogen-metabolising enzyme CYP1B1 suggests a detrimental role of oestrogens or oestrogen metabolites. We examined genetic and metabolic markers of altered oestrogen metabolism in subjects with a BMPR2 mutation. Genotypes for CYP1B1 Asn453Ser (N453S) were determined for 140 BMPR2 mutation carriers (86 females and 54 males). Nested from those subjects, a case-control study of urinary oestrogen metabolite levels (2-hydroxyoestrogen (2-OHE) and 16alpha-hydroxyoestrone (16alpha-OHE(1))) was conducted in females (five affected mutation carriers versus six unaffected mutation carriers). Among females, there was four-fold higher penetrance among subjects homozygous for the wild-type genotype (N/N) than those with N/S or S/S genotypes (p = 0.005). Consistent with this finding, the 2-OHE/16alpha-OHE(1) ratio was 2.3-fold lower in affected mutation carriers compared to unaffected mutation carriers (p = 0.006). Our findings suggest that variations in oestrogens and oestrogen metabolism modify FPAH risk. Further investigation of the role of oestrogens in this disease with profound sex bias may yield new insights and, perhaps, therapeutic interventions.

Identification and pharmacological characterization of the prostaglandin FP receptor and FP receptor variant complexes

Background and purpose: A prostamide analogue, bimatoprost, has been shown to be effective in reducing intraocular pressure, but its precise mechanism of action remains unclear. Hence, to elucidate the molecular mechanisms of this effect of bimatoprost, we focused on pharmacologically characterizing prostaglandin FP receptor (FP) and FP receptor variant (altFP) complexes.

Experimental approach: FP receptor mRNA variants were identified by reverse transcription-polymerase chain reaction. The FP-altFP4 heterodimers were established in HEK293/EBNA cells co-expressing FP and altFP4 receptor variants. A fluorometric imaging plate reader was used to study Ca²⁺ mobilization. Upregulation of cysteine-rich angiogenic protein 61 (Cyr61) mRNA was measured by Northern blot analysis, and phosphorylation of myosin light chain (MLC) by western analysis.

Key results: Six splicing variants of FP receptor mRNA were identified in human ocular tissues. Immunoprecipitation confirmed that the FP receptor is dimerized with altFP4 receptors in HEK293/EBNA cells co-expressing FP and altFP4 receptors. In the studies of the kinetic profile for Ca²⁺ mobilization, prostaglandin F_2α (PGF_2α) elicited a rapid increase in intracellular Ca²⁺ followed by a steady state phase. In contrast, bimatoprost elicited an immediate increase in intracellular Ca²⁺ followed by a second phase. The prostamide antagonist, AGN211335, selectively and dose-dependently inhibited the bimatoprost-initiated second phase of Ca²⁺ mobilization, Cyr61 mRNA upregulation and MLC phosphorylation, but did not block the action of PGF_2α.

Conclusion and implications: Bimatoprost lacks effects on the FP receptor but may interact with the FP-altFP receptor heterodimer to induce alterations in second messenger signalling. Hence, FP-altFP complexes may represent the underlying basis of bimatoprost pharmacology.

Tenascin-C is induced by mutated BMP type II receptors in familial forms of pulmonary arterial hypertension

Familial forms of human pulmonary arterial hypertension (FPAH) have been linked to mutations in bone morphogenetic protein (BMP) type II receptors (BMPR2s), yet the downstream targets of these receptors remain obscure. Here we show that pulmonary vascular lesions from patients harboring BMPR2 mutations express high levels of tenascin-C (TN-C), an extracellular matrix glycoprotein that promotes pulmonary artery (PA) smooth muscle cell (SMC) proliferation. To begin to define how TN-C is regulated, PA SMCs were cultured from normal subjects and from those with FPAH due to BMPR2 mutations. FPAH SMCs expressed higher levels of TN-C than normal SMCs. Similarly, expression of Prx1, a factor that drives TN-C transcription, was elevated in FPAH vascular lesions and SMCs derived thereof. Furthermore, Prx1 and TN-C promoter activities were significantly higher in FPAH vs. normal SMCs. To delineate how BMPR2s control TN-C, we focused on receptor (R)-Smads, downstream effectors activated by wild-type BMPR2s. Nuclear localization and phosphorylation of R-Smads was greater in normal vs. FPAH SMCs. As well, indirect blockade of R-Smad signaling with a kinase-deficient BMP receptor Ib upregulated TN-C in normal SMCs. Because ERK1/2 MAPKs inhibit the transcriptional activity of R-Smads, and because ERK1/2 promotes TN-C transcription, we determined whether ERK1/2 inhibits R-Smad signaling in FPAH SMCs and whether this activity is required for TN-C transcription. Indeed, ERK1/2 activity was greater in FPAH SMCs, and inhibition of ERK1/2 resulted in nuclear localization of R-Smads and inhibition of TN-C. These studies define a novel signaling network relevant to PAH underscored by BMPR2 mutations.

Bimatoprost: A Novel Antiglaucoma Agent

The aim of glaucoma therapy is to preserve vision by reducing intraocular pressure (IOP). Following recent National Eye Institute sponsored studies, it is becoming increasingly apparent that every mmHg of extra IOP lowering counts. Bimatoprost is the newest and most effective addition to the physician's armamentarium of ocular hypotensive drugs. Direct clinical comparisons have demonstrated that it is more efficacious than the prostaglandin (PG) FP receptor agonist prodrugs, latanoprost and travoprost, as well as a beta-adrenoceptor antagonist, timolol, alone or in fixed combination with the carbonic anhydrase inhibitor, dorzolamide. Moreover, patients that are refractory to latanoprost therapy may be successfully treated with bimatoprost. Such evidence provides support, at the clinical level, for the contention that bimatoprost is pharmacologically distinct from PG FP receptor agonist prodrugs. Bimatoprost is a structural analog of PGF2alpha-ethanolamide (prostamide F2alpha), which is formed from the endocannabinoid anandamide by a biosynthetic pathway involving cyclooxygenase-2 (COX-2). Their pharmacology is remarkably similar, such that bimatoprost may be regarded as a prostamide mimetic. The target receptor for bimatoprost and the prostamides appears unique and unrelated to PG- and endocannabinoid-sensitive receptors. Extensive ocular distribution/metabolism studies in non-human primates demonstrate that bimatoprost is not a prodrug, it remains essentially intact. Its profound ocular hypotensive effects may, therefore, be attributed to its prostamide-mimetic properties.

High frequency of BMPR2 exonic deletions/duplications in familial pulmonary arterial hypertension

RATIONALE

Previous studies have shown that approximately 55% of patients with familial pulmonary arterial hypertension (FPAH) have BMPR2 coding sequence mutations. However, direct sequencing does not detect other types of heterozygous mutations, such as exonic deletions/duplications.

OBJECTIVE

To estimate the frequency of BMPR2 exonic deletions/duplications in FPAH.

METHODS

BMPR2 mRNA from lymphoblastoid cell lines of 30 families with PAH and 14 patients with idiopathic PAH (IPAH) was subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) and sequencing. Sequencing of genomic DNA was used to identify point mutations in splice donor/acceptor sites. Multiplex ligation-dependent probe amplification (MLPA) was used to detect exonic deletions/duplications with verification by real-time PCR.

MEASUREMENTS AND MAIN RESULTS

Eleven (37%) patients with FPAH had abnormally sized RT-PCR products. Four of the 11 patients were found to have splice-site mutations resulting in aberrant splicing, and exonic deletions/duplications were detected in the remaining seven patients. MLPA identified three deletions/duplications that were not detectable by RT-PCR. Coding sequence point mutations were identified in 11 of 30 (37%) patients. Mutations were identified in 21 of 30 (70%) patients with FPAH, with 10 of 21 mutations (48%) being exonic deletions/duplications. Two of 14 (14%) patients with IPAH exhibited BMPR2 point mutations, whereas none showed exonic deletions/duplications.

CONCLUSIONS

Our study indicates that BMPR2 exonic deletions/duplications in patients with FPAH account for a significant proportion of mutations (48%) that until now have not been screened for. Because the complementary approach used in this study is rapid and cost effective, screening for BMPR2 deletions/duplications by MLPA and real-time PCR should accompany direct sequencing in all PAH testing.

Serotonin transporter polymorphisms in familial and idiopathic pulmonary arterial hypertension

RATIONALE

Serotonin is a pulmonary vasoconstrictor and smooth muscle cell mitogen. The serotonin transporter (SERT) is abundant in pulmonary vascular smooth muscle. Compared with the short (S) allele, the long (L) SERT promoter allele is associated with increased SERT transcription and more severe pulmonary hypertension in a cohort of patients with chronic obstructive pulmonary disease, and was more prevalent in a cohort with idiopathic pulmonary arterial hypertension (IPAH), compared with control subjects.

OBJECTIVE

We hypothesized that the SERT L allele would associate with an earlier age at diagnosis and/or shorter survival interval in pulmonary arterial hypertension (PAH) than the S allele.

METHODS

SERT promoters from 166 familial PAH (FPAH), 83 IPAH, and 125 control subjects were sequenced. One hundred twenty-seven of the patients with FPAH had a known mutation in bone morphogenetic protein receptor 2 (BMPR2).

RESULTS

The mean age at diagnosis was 35.8 yr in patients with FPAH and 41.1 yr in patients with IPAH (p = 0.02). There were no significant differences in distribution of the LL, LS, or SS genotypes in IPAH, FPAH, or unaffected BMPR2 mutation carriers. In FPAH, the LL genotype was associated with an earlier age at diagnosis (p < 0.02).

CONCLUSIONS

In patients with IPAH, these SERT genotypes do not correlate with age at diagnosis or survival interval. In patients with FPAH, the LL genotype correlates with an earlier age at diagnosis than SL or SS, although survival among the groups was similar. The correlation of the SERT promoter polymorphism with age at diagnosis in FPAH suggests a possible relationship between the SERT and BMPR2.

Gross BMPR2 gene rearrangements constitute a new cause for primary pulmonary hypertension

PURPOSE

Approximately 50% of patients with familial primary pulmonary hypertension (FPPH) have been reported to have mutations within the bone morphogenic protein receptor type 2 (BMPR2) gene. The vast majority of these mutations were identified by PCR amplification and sequencing of individual exons. The aim of our study was to determine if additional BMPR2 mutations not found by exon sequencing alone could account for a significant portion of these negative cases.

METHODS

We examined DNA samples from 12 families, previously found to be negative for BMPR2 mutations, to identify any large BMPR2 gene rearrangements.

RESULTS

Southern blot analysis found large gene rearrangements in four (33%) unrelated kindreds. Further analysis by reverse transcriptase PCR (RT-PCR) of BMPR2 transcripts from two of these kindreds found one to be heterozygous for a exon 10 duplication and the second to be heterozygous for a deletion of exons 4 to 5. Nonhomologous recombination is believed to be the cause of these large insertions/deletions.

CONCLUSION

Our results demonstrate the inherent problems associated with exon-by-exon sequencing and the importance of other screening methods such as Southern blot and RT-PCR in the identification of BMPR2 mutations.

Pharmacological characterization of a novel antiglaucoma agent, Bimatoprost (AGN 192024)

Replacement of the carboxylic acid group of prostaglandin (PG) F(2alpha) with a nonacidic moiety, such as hydroxyl, methoxy, or amido, results in compounds with unique pharmacology. Bimatoprost (AGN 192024) is also a pharmacologically novel PGF(2alpha) analog, where the carboxylic acid is replaced by a neutral ethylamide substituent. Bimatoprost potently contracted the feline lung parenchymal preparation (EC(50) value of 35-55 nM) but exhibited no meaningful activity in a variety of PG-sensitive tissue and cell preparations. Its activity seemed unrelated to FP receptor stimulation according to the following evidence. 1) Bimatoprost exhibited no meaningful activity in tissues and cells containing functional FP receptors. 2) Bimatoprost activity in the cat lung parenchyma is not species-specific because its potent activity in this preparation could not be reproduced in cells stably expressing the feline FP receptor. 3) Radioligand binding studies using feline and human recombinant FP receptors exhibited minimal competition versus [(3)H]17-phenyl PGF(2a) for Bimatoprost. 4) Bimatoprost pretreatment did not attenuate PGF(2alpha)-induced Ca(2+) signals in Swiss 3T3 cells. 5) Regional differences were apparent for Bimatoprost but not FP agonist effects in the cat lung. Bimatoprost reduced intraocular pressure in ocular normotensive and hypertensive monkeys over a 0.001 to 0.1% dose range. A single-dose and multiple-dose ocular distribution/metabolism studies using [(3)H]Bimatoprost (0.1%) were performed. Within the globe, bimatoprost concentrations were 10- to 100-fold higher in anterior segment tissues compared with the aqueous humor. Bimatoprost was overwhelmingly the predominant molecular species identified at all time points in ocular tissues, indicating that the intact molecule reduces intraocular pressure.

Neuroprotection of retinal ganglion cells by brimonidine in rats with laser-induced chronic ocular hypertension

PURPOSE

To examine the neuroprotective effect of the alpha(2)-adrenergic agonist brimonidine in a chronic ocular hypertension model.

METHODS

Intraocular pressure (IOP) was elevated by laser photocoagulation of episcleral and limbal veins. Retinal ganglion cell loss was evaluated in wholemounted retinas. Brimonidine or timolol was administered, either at the time of or 10 days after IOP elevation and continued for 3 weeks. Drug-related immunohistochemical changes in glial fibrillary acidic protein (GFAP) were also determined after 3 weeks.

RESULTS

Laser treatment caused a twofold IOP increase over baseline that was maintained for 2 months. A time-dependent loss of ganglion cells occurred with elevated IOP. Systemic administration of brimonidine or timolol caused little decrease in IOP. After 3 weeks of elevated IOP, ganglion cell loss in control rats was 33% +/- 3%. Brimonidine reduced the progressive loss of ganglion cells to 26% +/- 1% and 15% +/- 2% at doses of 0.5 and 1 mg/kg. d, respectively. Timolol had no effect. Ten days of high IOP resulted in 22% +/- 4% ganglion cell loss. Brimonidine administration initiated 10 days after IOP elevation prevented any further loss of ganglion cells. In vehicle- or timolol-treated rats, ganglion cell loss continued to 33%. The increase in immunoreactivity of GFAP in ocular hypertensive retinas was attenuated by brimonidine.

CONCLUSIONS

Systemic application of brimonidine or timolol had little effect on IOP. Brimonidine, but not timolol, showed significant protection of retinal ganglion cells when applied at the time of IOP elevation and prevented further cell loss when applied after IOP was elevated. This indicates that brimonidine has a neuroprotective activity unrelated to its effect on ocular hypotension.

Role of alpha-2 adrenergic receptors in neuroprotection and glaucoma

The loss of retinal ganglion cells (RGCs) in glaucoma occurs progressively over many years. A neuroprotective drug should enhance survival of RGCs in the presence of chronic stress/injury. Four criteria are proposed for assessing the likely therapeutic utility in human glaucoma of drugs that have demonstrated neuroprotective activity in animal models: 1) A specific receptor target must be in the retina/optic nerve; 2) Activation of the target must trigger pathways that enhance a neuron's resistance to stress/injury and/or suppresses toxic insults; 3) The drug must reach the retina/vitreous at pharmacologic doses; and 4) The neuroprotective activity should be demonstrated in clinical trials. Data are presented that illustrate how the specific and potent alpha-2 agonist, brimonidine, meets these criteria. The alpha-2A receptor was localized in the inner rat retina by immunohistochemistry. Brimonidine reduced the rate of RGC loss in the calibrated rat optic nerve injury model even when dosed 12 and 24 hours before injury, consistent with a long-term enhancement of RGC resistance to stress. Brimonidine was also neuroprotective in the lasered chronic hypertensive rat model, reducing RGC loss over three weeks from 33% to 15%. A clinical trial has been initiated to determine brimonidine's neuroprotective activity in patients with non-arteritic ischemic optic neuropathy.

Alpha-2 adrenergic receptor agonists are neuroprotective in experimental models of glaucoma

PURPOSE

The glaucomas are characterized by chronic progressive ganglion cell loss over many years. A drug with neuroprotective activity should increase the resistance of retinal ganglion cells (RGC) to chronic stress or injury and therefore enhance survival. Brimonidine is a highly selective and potent alpha-2 adrenergic receptor agonist, which lowers intra-ocular pressure (IOP) and is neuroprotective. Immunohistochemistry data have shown that the specific receptor targets, the alpha-2 receptors, are located in the inner retina.

METHODS

Brimonidine 0.1 mg/kg given intraperitoneally promoted RGC survival compared with vehicle using the optic nerve crush model even when administered up to 24 hours before injury. Using the chronic ocular hypertensive rat model, brimonidine 1 mg/kg/day (with osmotic pump) significantly prevented the loss of RGCs when compared with vehicle or timolol. This ability was due to the neuroprotective action of brimonidine, since it did not affect IOP. In addition, brimonidine 0.1 mg/day reached concentrations in the retina of Sprague-Dawley rats within 30 minutes of injection, which was sufficient to activate the alpha-2 receptor (> or = 2 nM) and maintained these concentrations for 6 hours.

CONCLUSIONS

Having demonstrated that: a. the specific receptor target of brimonidine is located in the retina, which is important for optic neuroprotection, b. the agent shows neuroprotective ability in animal models, c. pharmacological concentrations of the drug can be reached in the retina, clinical trial has been initiated to determine whether brimonidine is neuroprotective in patients with nonarteritic ischaemic optic neuropathy.

Differential effects of alpha-adrenoceptor agonists on human retinal microvessel diameter

The effects of locally administered brimonidine, clonidine, and p-aminoclonidine on microvessel caliber were compared in human retinal tissues grafted into the hamster cheek pouch. Clonidine and p-aminoclonidine, but not brimonidine, potently constricted human retinal microvessels over a broad concentration range. All three agonists elicited significant vasoconstriction in naive hamster cheek pouch microvasculature. The alpha2-adrenoceptor antagonist, rauwolscine, inhibited p-aminoclonidine-induced constriction in naive hamster cheek pouch microvessels, but not p-aminoclonidine-induced effects in retinal grafts. Selective alpha1-adrenoceptor agonists evoked vasoconstriction in retinal grafts only at relatively high concentrations. These differential effects on the retinal microvasculature could not be readily explained solely on the basis of alpha1- or alpha2-adrenoceptor involvement. Clonidine, p-aminoclonidine and brimonidine are also imidazoline derivatives that interact with putative non-adrenergic imidazoline-sensitive binding sites, the so-called I1-imidazoline binding site subtype implicated by some investigators in mediation of peripheral vasoconstriction. As with p-aminoclonidine, the potent vasoconstriction in human retinal microvasculature elicited by moxonidine, an alpha-adrenergic agonist that has also been reported to exhibit selectivity for putative I1-imidazoline binding sites, was not inhibited by the selective alpha-adrenoceptor antagonist, rauwolscine, nor by idazoxan, an antagonist characterized as having substantial activity at putative I2-imidazoline binding sites. These data suggest the possible involvement of an unconventional non-adrenergic imidazoline-sensitive pathway in regulation of microvascular responses in the inner retina, and that drug activity mediated via such an imidazoline-sensitive component could potentially evoke deleterious effects in the retinal microvasculature.

The pharmacology of bimatoprost (Lumigan)

Bimatoprost (Lumigan) is a pharmacologically unique and highly efficacious ocular hypotensive agent. It appears to mimic the activity of a newly discovered family of fatty acid amides, termed prostamides. One biosynthetic route to the prostamides involves anandamide as the precursor. Bimatoprost pharmacology has been extensively characterized by binding and functional studies at more than 100 drug targets, which comprise a diverse variety of receptors, ion channels, and transporters. Bimatoprost exhibited no meaningful activity at receptors known to include antiglaucoma drug targets as follows: adenosine (A(1-3)), adrenergic (alpha(1), alpha(2), beta(1), beta(2)), cannabinoid (CB(1), CB(2)), dopamine (D(1-5)), muscarinic (M(1-5)), prostanoid (DP, EP(1-4), FP, IP, TP), and serotonin (5HT(1-7)). Bimatoprost does, however, exhibit potent inherent pharmacological activity in the feline iris sphincter preparation, which is prostamide-sensitive. Bimatoprost also resembles the prostamides in that it is a potent and highly efficacious ocular hypotensive agent. A single dose of bimatoprost markedly reduces intraocular pressure in dogs and laser-induced ocular hypertensive monkeys. Decreases in intraocular pressure are well maintained for at least 24 hr post-dose. Human studies have demonstrated that systemic exposure to bimatoprost is low and that accumulation does not occur. The sclera is the preferred route of accession to the eye. The high scleral permeability coefficient Papp is a likely contributing factor to the rapid onset and long-acting ocular hypotensive profile of bimatoprost.

Vaccination for protection of retinal ganglion cells against death from glutamate cytotoxicity and ocular hypertension: implications for glaucoma

Our group recently demonstrated that autoimmune T cells directed against central nervous system-associated myelin antigens protect neurons from secondary degeneration. We further showed that the synthetic peptide copolymer 1 (Cop-1), known to suppress experimental autoimmune encephalomyelitis, can be safely substituted for the natural myelin antigen in both passive and active immunization for neuroprotection of the injured optic nerve. Here we attempted to determine whether similar immunizations are protective from retinal ganglion cell loss resulting from a direct biochemical insult caused, for example, by glutamate (a major mediator of degeneration in acute and chronic optic nerve insults) and in a rat model of ocular hypertension. Passive immunization with T cells reactive to myelin basic protein or active immunization with myelin oligodendrocyte glycoprotein-derived peptide, although neuroprotective after optic nerve injury, was ineffective against glutamate toxicity in mice and rats. In contrast, the number of surviving retinal ganglion cells per square millimeter in glutamate-injected retinas was significantly larger in mice immunized 10 days previously with Cop-1 emulsified in complete Freund's adjuvant than in mice injected with PBS in the same adjuvant (2,133 +/- 270 and 1,329 +/- 121, respectively, mean +/- SEM; P < 0.02). A similar pattern was observed when mice were immunized on the day of glutamate injection (1,777 +/- 101 compared with 1,414 +/- 36; P < 0.05), but not when they were immunized 48 h later. These findings suggest that protection from glutamate toxicity requires reinforcement of the immune system by antigens that are different from those associated with myelin. The use of Cop-1 apparently circumvents this antigen specificity barrier. In the rat ocular hypertension model, which simulates glaucoma, immunization with Cop-1 significantly reduced the retinal ganglion cell loss from 27.8% +/- 6.8% to 4.3% +/- 1.6%, without affecting the intraocular pressure. This study may point the way to a therapy for glaucoma, a neurodegenerative disease of the optic nerve often associated with increased intraocular pressure, as well as for acute and chronic degenerative disorders in which glutamate is a prominent participant.

alpha(2)-Adrenoceptor agonists inhibit vitreal glutamate and aspartate accumulation and preserve retinal function after transient ischemia

Recent studies have suggested that alpha(2)-adrenergic agonists prevent neuronal cell death in a number of animal models, although the mechanism of alpha(2)-neuroprotection remains unclear. In a retinal ischemia model, the alpha(2)-specific agonist brimonidine (1 mg/kg i.p.) preserves approximately 80% of the electroretinogram (ERG) b-wave. The protective effect of brimonidine is completely blocked by coadministration of the alpha(2)- antagonist rauwolscine. Brimonidine treatment preserves the ERG b-wave if animals are treated 1 or 3 h before ischemia, but has no effect if it is injected during ischemia. The 3-h pretreatment effect is blocked by i.v. injection of rauwolscine 2 h later (1 h before ischemia). A comparison of vitreous humor glutamate levels between untreated and brimonidine-treated eyes shows that 1) after ischemia, glutamate levels rise 2- to 3-fold in the untreated animals, and 2) glutamate levels in the brimonidine-treated animals are comparable to the nonischemic controls. Hence, the mechanism for brimonidine-mediated protection in the retinal ischemia model requires activation of the alpha(2)-adrenergic receptors immediately before and during ischemia. These data suggest that activation of the alpha(2)-adrenergic receptor may reduce ischemic retinal injury by preventing the accumulation of extracellular glutamate and aspartate.

RGC death in mice after optic nerve crush injury: oxidative stress and neuroprotection

PURPOSE

To establish a method for morphometric analysis of retrogradely labeled retinal ganglion cells (RGCs) of the mouse retina, to be used for the study of molecular aspects of RGC survival and neuroprotection in this model; to evaluate the effect of overexpression of Cu-Zn-superoxide dismutase (CuZnSOD) on RGC survival after severe crush injury to the optic nerve, and to assess the effect of the alpha2-adrenoreceptor agonist brimonidine, recently shown to be neuroprotective, on RGC survival.

METHODS

A severe crush injury was inflicted unilaterally in the orbital portion of the optic nerves of wild-type and transgenic (Tg-SOD) mice expressing three to four times more human CuZnSOD than the wild type. In each mouse all RGCs were labeled 72 hours before crush injury by stereotactic injection of the neurotracer dye FluoroGold (Fluorochrome, Denver, CO) into the superior colliculus. Survival of RGCs was then assessed morphometrically, with and without systemic injection of brimonidine.

RESULTS

Two weeks after crush injury, the number of surviving RGCs was significantly lower in the Tg-SOD mice (596.6 +/- 71.9 cells/mm(2)) than in the wild-type control mice (863. 5 +/- 68 cells/mm(2)). There was no difference between the numbers of surviving RGCs in the uninjured retinas of the two strains (3708 +/- 231.3 cells/mm(2) and 3904 +/- 120 cells/mm(2), respectively). Systemic injections of brimonidine significantly reduced cell death in the Tg-SOD mice, but not in the wild type.

CONCLUSIONS

Overexpression of CuZnSOD accelerates RGC death after optic nerve injury in mice. Activation of the alpha2-adrenoreceptor pathway by brimonidine enhances survival of RGCs in an in vivo transgenic model of excessive oxidative stress.

Replacement of the carboxylic acid group of prostaglandin f(2alpha) with a hydroxyl or methoxy substituent provides biologically unique compounds

Replacement of the carboxylic acid group of PGF(2alpha) with the non-acidic substituents hydroxyl (-OH) or methoxy (-OCH(3)) resulted in an unexpected activity profile. Although PGF(2alpha) 1-OH and PGF(2alpha) 1-OCH(3) exhibited potent contractile effects similar to 17-phenyl PGF(2alpha) in the cat lung parenchymal preparation, they were approximately 1000 times less potent than 17-phenyl PGF(2alpha) in stimulating recombinant feline and human FP receptors. In human dermal fibroblasts and Swiss 3T3 cells PGF(2alpha) 1-OH and PGF(2alpha) 1-OCH(3) produced no Ca(2+) signal until a 1 microM concentration was exceeded. Pretreatment of Swiss 3T3 cells with either 1 microM PGF(2alpha) 1-OH or PGF(2alpha) 1-OCH(3) did not attenuate Ca(2+) signal responses produced by PGF(2alpha) or fluprostenol. In the rat uterus, PGF(2alpha) 1-OH was about two orders of magnitude less potent than 17-phenyl PGF(2alpha) whereas PGF(2alpha) 1-OCH(3) produced only a minimal effect. Radioligand binding studies on cat lung parenchymal plasma membrane preparations suggested that the cat lung parenchyma does not contain a homogeneous population of receptors that equally respond to PGF(2alpha)1-OH, PGF(2alpha)1-OCH(3), and classical FP receptor agonists. Studies on smooth muscle preparations and cells containing DP, EP(1), EP(2), EP(3), EP(4), IP, and TP receptors indicated that the activity of PGF(2alpha) 1-OH and PGF(2alpha) 1-OCH(3) could not be ascribed to interaction with these receptors. The potent effects of PGF(2alpha) 1-OH and PGF(2alpha) 1-OCH(3) on the cat lung parenchyma are difficult to describe in terms of interaction with the FP or any other known prostanoid receptor.

Pseudomesotheliomatous carcinoma involving pleura and peritoneum: A clinicopathologic and immunohistochemical study of three cases

Pseudomesotheliomatous carcinoma is a rare variant of peripheral adenocarcinoma of the lung that can manifest clinical, radiologic, and pathologic features similar to malignant mesothelioma. We present three patients with pseudomesotheliomatous carcinoma of the lung. In one patient the carcinoma extended beyond the thorax and extensively involved the peritoneum, mesentery, omentum, and intestines. All patients experienced weight loss and chest pain. All were white men aged 63, 65, and 67 years. Two were smokers and had shortness of breath, cough, and pleural effusion. One had a history of asbestos exposure. No patient developed dyspnea or hemoptysis. One was successfully treated for prostatic carcinoma 18 months earlier. Radiographically, all tumors were pleura-based. Grossly, the tumors spread extensively over pleural (and in one case peritoneal) surfaces and mimicked malignant mesothelioma. Histologically, all tumors were poorly differentiated and necrotic; two tumors exhibited spindle-cell components and desmoplasia. Mucin production was detectable in none, 10%, and 50% of tumor cells. The percentages of tumor cells immunoreactive for Ber-EP4 were 70%, 100%, and 80%; for Leu MI 0%, 90%, and 50%; for epithelial membrane antigen 80%, 80%, and 100%; for B 72.3%, 0%, 90%, and 20%; for polyclonal carcinoembryonic antigen 0%, 10%, and 10%; and for monoclonal 5%, 0%, and 0%. Of these, Ber-EP4 and B 72.3 rendered the most reliable diagnostic results. The clinical, radiologic, and gross and routine histologic findings were similar to those of a malignant mesothelioma; the final diagnosis could be made based mainly on immunocytochemical results. We have reviewed the English and German literature regarding 65 such tumors and present our experience with three additional cases. We emphasize the application of immunocytochemical studies on pleura-based poorly or undifferentiated malignant tumors of unknown origin.

Amputation prevention by vascular surgery and podiatry collaboration in high-risk diabetic and nondiabetic patients. The Operation Desert Foot experience

OBJECTIVE

To describe a unique multidisciplinary outpatient intervention for patients at high risk for lower-extremity amputation.

RESEARCH DESIGN AND METHODS

Patients with foot ulcers and considered to be high risk for lower-extremity amputation were referred to the High Risk Foot Clinic of Operation Desert Foot at the Carl T. Hayden Veterans Affairs' Medical Center in Phoenix, Arizona, where patients received simultaneous vascular surgery and podiatric triage and treatment. Some 124 patients, consisting of 90 diabetic patients and 34 nondiabetic patients, were initially seen between 1 October 1991 and 30 September 1992 and followed for subsequent rate of lower-extremity amputation.

RESULTS

In a mean follow-up period of 55 months (range 3-77), only 18 of 124 patients (15%) required amputation at the level of the thigh or leg. Of the 18 amputees, 17 (94%) had type 2 diabetes. The rate of avoiding limb loss was 86.5% after 3 years and 83% after 5 years or more. Furthermore, of the 15 amputees surviving longer than 2 months, only one (7%) had to undergo amputation of the contralateral limb over the following 12-65 months (mean 35 months). Compared with nondiabetic patients, patients with diabetes had a 7.68 odds ratio for amputation (95% CI 5.63-9.74) (P < 0.01).

CONCLUSIONS

A specialized clinic for prevention of lower-extremity amputation is described. Initial and contralateral amputation rates appear to be far lower in this population than in previously published reports for similar populations. Relative to patients without diabetes, patients with diabetes were more than seven times as likely to have a lower-extremity amputation. These data suggest that aggressive collaboration of vascular surgery and podiatry can be effective in preventing lower-extremity amputation in the high-risk population.

Alpha2-adrenoreceptor agonists are neuroprotective in a rat model of optic nerve degeneration

PURPOSE

The neurodegenerative progression of glaucoma is considered to be related not only to primary risk factors such as the elevation of intraocular pressure, but also to mediators of secondary neuronal degeneration. In the present study, the neuroprotective activity of the alpha2-adrenoreceptor agonists brimonidine, AGN 191103, and clonidine were examined in an animal model that simulates secondary neuronal degeneration of the optic nerve in a way thought to be independent of elevation of intraocular pressure. The beta-blocker timolol, currently used clinically to decrease intraocular pressure, was also examined for neuroprotective activity at dosages corresponding to the effective antihypertensive dosage.

METHODS

A single dose of each of the tested compounds was administered intraperitoneally immediately after partial crush injury of the rat optic nerve. Secondary degeneration was measured by determining injury-induced deficits with and without the drug. This was achieved electrophysiologically by measurement of compound action potential amplitude, and morphometrically by counting the retrogradely labeled retinal ganglion cells, representing viable optic nerve axons, in wholemounted retinas.

RESULTS

All three alpha2-adrenoreceptor agonists, but not timolol, exhibited neuroprotective effects. Treatment immediately after injury with each of these agonists resulted in a dose-dependent attenuation of the injury-induced decrease in compound action potential amplitude. Moreover, after treatment with 100 microg/kg brimonidine administered intraperitoneally, the loss of retinal ganglion cells 2 weeks after injury was three times lower than in saline-treated animals.

CONCLUSIONS

In addition to their known effect of lowering intraocular pressure, alpha2-adrenoreceptor agonists, unlike timolol, exert a neuroprotective effect. Use of the rat optic nerve model of partial crush injury can serve as a method of screening compounds that are potentially capable of alleviating the progression of secondary neuronal degeneration.

Synthesis and evaluation of 2-(arylamino)imidazoles as alpha 2-adrenergic agonists

A series of 2-(arylamino)imidazoles was synthesized and evaluated for activity at alpha 1- and alpha 2-adrenoceptors. This class of agents has been shown to have potent and selective agonist activity at the alpha 2-adrenoceptors. The most potent member of this class, 2-[(5-methyl-1,4-benzodioxan-6yl)amino]imidazole, proved efficacious for the reduction of intraocular pressure upon topical administration and for the reduction of blood pressure upon intravenous administration. During the course of our studies, we developed a new reagent that allowed rapid assembly of the target compounds. This reagent, N-(2,2-diethoxyethyl)carbodiimide, was convenient to prepare and was stable under low-temperature storage conditions.

In-vivo activity and enzymatic hydrolysis of novel prostaglandin F2 alpha prodrugs in ocular tissues

Enzymatic hydrolysis and in-vivo ocular studies were performed on a novel series of prostaglandin F2 alpha (PGF2 alpha) pivaloyl ester prodrugs to assess their therapeutic potential. These novel PGF2 prodrugs were esterified at the 9-, 11-, and 15-OH positions. Their enzymatic hydrolysis rates were compared to PGF2 alpha 1-isopropyl ester in dog, monkey, and human ocular tissues. Intraocular pressure (IOP) studies were performed in monkeys and dogs, and ocular surface hyperemia was monitored in dogs. PGF2 alpha 9-monopivaloyl ester was not enzymatically hydrolysed in dog and human ocular tissues. PGF2 alpha 11- and 15-monopivaloyl esters and PGF2 alpha 11,15-dipivaloyl ester were converted to PGF2 alpha by all ocular tissues at a substantially slower rate than PGF2 alpha l-isopropyl ester. Despite their slow enzymatic hydrolysis rates, the ocular hypotensive activity of PGF2 alpha mono and dipivaloyl esters, where positions 11- and 15- were functionalized, closely approached the activity achieved with PGF2 alpha l-isopropyl ester. The degree of ocular surface hyperemia associated with PGF2 alpha 11-pivaloyl ester and PGF2 alpha 11,15-dipivaloyl ester was less than that associated with equivalent doses of PGF2 alpha l-isopropyl ester. It appears that rapid enzymatic hydrolysis rates are not necessary to obtain efficacious ocular hypotensive PGF2 alpha ester prodrugs. Slow enzymatic hydrolysis rates may assist in reducing the degree of ocular surface hyperemia. A further contributory factor in this regard could be the approximately ten-fold favorable difference in enzymatic hydrolysis rates between iris-ciliary body and conjunctival tissue for these novel pivaloyl esters of PGF2 alpha. These factors appear to translate into an improved therapeutic index for separating ocular hypotensive and ocular surface hyperemic effects.

Synthesis and evaluation of 2-[(5-methylbenz-1-ox-4-azin-6-yl)imino]imidazoline, a potent, peripherally acting alpha 2 adrenoceptor agonist

We have synthesized 2-[(5-methylbenz-1-ox-4-azin-6-yl)imidazoline, 3, a potent, peripherally acting alpha 2 adrenoceptor agonist. The agent is conveniently prepared in five steps from 2-amino-m-cresol. The agent has demonstrated good selectivity for alpha 2 adrenoceptors in binding and functional studies. When applied topically to eyes, the agent is efficacious for the reduction of intraocular pressure. The agent does not penetrate the blood-brain barrier and, as a consequence, does not lower blood pressure or induce sedation when administered topically or intravenously. We have determined the pKa and log P in water versus both octanol and dodecane of 3 and a set of related agents. The best physical parameter to explain its lack of central nervous system penetration appears to be log P measured in octanol versus water.

The antiinflammatory activity of topically applied novel calcium-channel antagonists

The antiinflammatory activities of two novel calcium-channel antagonists, AGN 190742 and AGN 190744, were evaluated in murine models of cutaneous inflammation. These 2(5H)-furanone ring compounds block both depolarization-dependent Ca2+ entry and receptor-mediated responses in GH3 cells. Topical application of AGN 190742 or AGN 190744 inhibits neutrophil infiltration and epidermal hyperplasia induced by repeated treatment of mouse skin with phorbol ester. AGN 190744 also is active in an arachidonic acid model of acute inflammation. These data suggest that topical application of calcium-channel antagonists can inhibit cutaneous inflammatory responses and that AGN 190742 and/or AGN 190744 may serve as useful pharmacological probes for examining these responses in vivo.

Effect of platelet-derived growth factor on rabbit corneal wound healing

Human recombinant platelet-derived growth factor was evaluated with the use of wound healing models in New Zealand albino rabbits. The efficacy of the platelet-derived growth factor dimers, AA, AB, and BB, was determined in corneal reepithelialization and anterior keratectomy models which examined the healing response in the presence or absence of the basement membrane. All dimers increased the rate of wound healing in both models at 100 microg/ml when compared with control; however, the platelet-derived growth factor-BB isoform showed the most dramatic increase in both studies. The strength of the healing stroma after incision was evaluated by means of a tensile strength model. Histologic evaluation of the stromal wound area after 9 days of healing showed a marked increase in the number of keratocytes within the wound bed of the corneas treated with platelet-derived growth factor-BB when compared with control corneas. In addition, at 9 days, the epithelial plug was still present in the control corneas but had been extruded to the surface by the granulation tissue in the platelet-derived growth factor-BB-treated corneas. These results are indicative of a more advanced stage of healing in treated versus control wounds at 9 days after the operation. A 30% increase in corneal tensile strength versus control was noted after 21 days of healing. Finally, in an in vitro gel contraction assay, platelet-derived growth factor exhibited a dose-dependent effect on the contraction of fibroblasts for doses ranging from 0.01 to 10 ng/ml. These results indicate that platelet-derived growth factor is active in the corneal wound healing process.

How Do Older Nurses Perceive Their Clinical Competence and the Effects of Age?

In 1996, the first of the baby boomer population bulge that includes registered nurses (RNs) will reach age 50. Considering the prevailing negative stereotypes about women, nurses, and older adults in general, it is necessary to understand the abilities and needs of older nurses. This qualitative study was the first stage of a needs assessment of professionally mature RNs. Eight female RNs, employed full-time in an acute care setting and over age 50, were interviewed to determine their perceptions, attitudes, and beliefs about their own professional competence and how they believed they were perceived by others. Results indicated that older RNs felt good about themselves and the profession, and valued traditional bedside nursing and professional behaviors. Of the eight recurring themes found, the need for continuing education generated the most discussion. Will the methods and resources of the past meet the educational needs of the older nurses? Further study is recommended to discover their needs and the needs of their employers.

Synthesis and carbonic anhydrase inhibitory activity of 4-substituted 2-thiophenesulfonamides

A series of 4-substituted 2-thiophenesulfonamides was prepared from 3-thiophenecarboxaldehyde using metalation chemistry developed for 3-furaldehyde. Several of these compounds inhibit carbonic anhydrase II in vitro at concentrations of less than 10 nM. In addition, none of these compounds exhibit sensitization potential as determined from in vitro measurement of cysteine reactivity.

Agonist-sensitive and -insensitive intracellular Ca2+ pools. Separate Ca(2+)-releasing mechanisms revealed by manoalide and benzohydroquinone

The mechanism of action of a novel compound, 2,5-di-(t-butyl)-1,4-benzohydroquinone (BHQ), used to modulate cell free cytosolic Ca2+ concentration ([Ca2+]i) was studied in AR42J cells and pancreatic acini by using single-cell fluorescence techniques applied to Fura-2-loaded cells. In the presence of extracellular Ca2+ (Ca(2+)out), BHQ induced a biphasic [Ca2+]i increase, an initial and rapid transient followed by a sustained increase. The initial increase was due to Ca2+ release from intracellular stores, being independent of Ca(2+)out. The sustained response was due to Ca2+ entry, being dependent on Ca(2+)out, blocked by La3+ and correlated with an increased rate of Mn2+ entry, all indicative of increased plasma-membrane permeability to Ca2+. Treatment of AR42J cells with BHQ for about 5 min reversibly blocked agonist-dependent Ca2+ release and oscillations, whereas agonist pretreatment decreased, but did not prevent, the effects of BHQ on [Ca2+]i. Accordingly, depletion of the Ins(1,4,5)P3-mobilizable pool in permeabilized AR42J cells by BHQ required 5 min of incubation, although inhibition of the internal Ca2+ pump by BHQ was rapid. These observations suggest that BHQ mobilized an additional intracellular Ca2+ pool that did not respond to changes in Ins(1,4,5)P3. Manoalide, an inhibitor of Ca2+ channels, inhibited agonist-evoked [Ca2+]i oscillation and [Ca2+]i increase in a dose- and time-dependent manner without significant effect on internal Ca2+ pumps and Ca2+ content of the internal stores. Manoalide also inhibited the BHQ-evoked [Ca2+]i increase in the absence and presence of Ca(2+)out. Neither BHQ nor manoalide affected Ins(1,4,5)P3 levels in resting or stimulated cells. Therefore, the effect of BHQ appears to involve unmasking of passive Ca(2+)-permeation pathways in the plasma and intracellular membranes that do not respond to cholecystokinin octapeptide, following its described inhibition of the internal-store Ca2+ pumps responsible for accumulating Ca2+ in these pools.

AGN 190383, a novel phospholipase inhibitor with topical anti-inflammatory activity

AGN 190383 is a 5-hydroxy-2(5H)-furanone ring analog of the marine natural product manoalide. When applied topically, AGN 190383 inhibits phorbol ester induced mouse ear edema. It is a potent inhibitor of bee venom phospholipase A2 and blocks the release of arachidonic acid from calcium ionophore A23187 stimulated human neutrophils. AGN 190383 also inhibits both hormone-operated and depolarization-dependent calcium mobilization in GH3 cells, as well as fMLP stimulated increases in free cytosolic calcium in human PMNs. Furthermore, it is also able to block the release of the neutral protease elastase from stimulated neutrophils. The effects of AGN 190383 on arachidonic acid metabolism and leukocyte function may account, in part, for its anti-inflammatory activity in vivo.

Transforming growth factor alpha: in vivo release by normal human skin following UV irradiation and abrasion

Transforming growth factor alpha (TGF alpha) is a keratinocyte-growth-stimulating factor which may have a role in epidermal hyperproliferation, psoriasis, and wound healing. Since increased epidermal proliferation occurs in response to UV radiation, we have measured the amount of TGF alpha in exudates from normal and UVB-irradiated human skin. Cutaneous exudates were obtained using the skin chamber abrasion technique from one side of the back of volunteers (n = 10) with normal skin (collected following skin contact times of 2 and 30 min). Exudates were similarly obtained from the contralateral side of the back at sites irradiated 2 h previously with 3 x the minimum erythemal dose UVB. Levels of TGF alpha were measured by radioimmunoassay. Normal human skin released TGF alpha immediately after abrasion: unirradiated, 63 +/- 18 ng/ml; irradiated, 89 +/- 15 ng/ml. Levels of TGF alpha increased within 30 min to 110 +/- 14 ng/ml in unirradiated skin and to 190 +/- 17 ng/ml in irradiated skin. Irradiated sites at 30-min time points were significantly higher (p less than 0.05) than all other samples. The presence of releasable TGF alpha in normal skin suggests a role for TGF alpha in wound repair mechanisms.

Synthesis of chiral and achiral pyranenamine derivatives. Potent agents with topical ocular antiallergic activity

The SS, RR and meso stereoisomers of pyranenamine SK&F 84210 were synthesized stereospecifically starting from commercially available (R)-(-)- or (S)-(+)-2,2-dimethyl-1,3-dioxolane-4-methanol. In addition, two achiral pyranenamines 19 and 26 were also synthesized. When evaluated by intravenous and topical routes in the rat passive ocular anaphylaxis (POA) assay, (SS)- and meso-2 as well as achiral compounds 19 and 26 were found to be more potent antiallergic agents than (RR)-2.

Inhibition by manoalide of fMLP-stimulated elastase release from human neutrophils

Incubation of human polymorphonuclear leukocytes (PMNLs) with the chemotactic factor N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) resulted in a concentration-dependent release of the neutral protease elastase. This response was inhibited by pretreatment of the PMNLs with manoalide (IC50 approximately 0.08 microM). To understand the mechanism of this inhibition, we examined the effect of manoalide on the signal-transduction pathway believed to mediate fMLP stimulation. We observed in fura-2 loaded cells that pretreatment with manoalide blocked fMLP-induced increases in cytosolic free-calcium (IC50 approximately 0.15 microM). However, manoalide had no effect on inositol 1,4,5-trisphosphate (IP3) production at concentrations which completely inhibited the Ca2+ signal. Furthermore, manoalide was approximately 50-fold less potent as an inhibitor of phospholipase C activity in membrane preparations of PMNLs than as an inhibitor of calcium mobilization in whole cells. These data indicate that manoalide can block stimulation of human PMNLs through inhibition of Ca2+ mobilization, but that this occurs at a site beyond phospholipase C activation and inositol phosphate turnover.

Role of protein kinase C in the regulation of cytosolic Ca2+ in A431 cells: separation of growth factor and bradykinin pathways

Calcium signaling systems in nonexcitable cells involve activation of Ca2+ entry across the plasma membrane and release from intracellular stores as well as activation of Ca2+ pumps and inhibition of passive Ca2+ pathways to ensure exact regulation of free cytosolic Ca2+ concentration [( Ca2+]i). A431 cells loaded with fura-2 cells were used as a model system to examine regulation of Ca2+ entry and intracellular release. Epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) both stimulated Ca2+ entry and release while bradykinin appeared only to release Ca2+ from intracellular stores. The possible role of protein kinase C (PKC) in modulating the [Ca2+]i response to these agonists was examined by four methods. Low concentrations of TPA (2 x 10(-10) M) had no effect on Ca2+ release due to EGF, TGR-alpha or bradykinin but resulted in a rapid return of [Ca2+]i to baseline levels for EGF or TGF-alpha. Addition of the PKC inhibitor staurosporine (1 and 10 nM) completely inhibited the action of TPA on EGF-induced [Ca2+]i changes. An inhibitor of diglyceride kinase (R59022) mimicked the action of TPA. Down-regulation of PKC by overnight incubation with 0.1 or 1 microM TPA produced the converse effect, namely prolonged Ca2+ entry following stimulation with EGF or TGF-alpha. To show that one effect of TPA was on Ca2+ entry, fura-2 loaded cells were suspended in Mn2+ rather than Ca2+ buffers. Addition of EGF or TGF-alpha resulted in Ca2+ release and Mn2+ entry. TPA but not the inactive phorbol ester, 4-alpha-phorbol-12,13-didecanoate, inhibited the Mn2+ influx. Thus, PKC is able to regulate Ca2+ entry due to EGF or TGF-alpha in this cell type. A431 cells treated with higher concentrations of TPA (5 x 10(-8) M) inhibited not only Ca2+ entry but also Ca2+ release due to EGF/TGF-alpha but had no effect on bradykinin-mediated Ca2+ release, suggesting differences in the regulation of the intracellular stores responsive to these two classes of agonists. Furthermore, sequential addition of EGF or TGF-alpha gave a single transient of [Ca2+]i, showing a common pool of Ca2+ for these agonists. In contrast, sequential addition of EGF (or TGF-alpha) and bradykinin resulted in two [Ca2+]i transients equal in size to those obtained with a single agonist.(ABSTRACT TRUNCATED AT 400 WORDS)

Novel dihydrofolate reductases isolated from epidemic strains of trimethoprim/sulfamethoxazole-resistant Shigella sonnei

Two strains of trimethoprim-resistant Shigella sonnei bearing R plasmids pBH600 and pBH700 each elaborated a dihydrofolate reductase (DHFR) and were moderately resistant to trimethoprim (minimum inhibitory concentrations, 128 and 256 micrograms/ml, respectively). Neither plasmid hybridized to probes for DHFR types I, II, or III. The trimethoprim resistance genes from the R plasmids resided on a 1600-base pair (bp) PstI fragment of pBH600 and an 1800-bp PstI fragment of pBH700. Isoelectric focusing showed distinct isoelectric points for the enzymes coded for on pBH600 (5.3) and pBH700 (5.6-5.7). Trimethoprim-resistant S. sonnei from 10 locations in nine states were examined. Isolates from 8 locations hybridized only to a pBH700-derived probe and one isolate hybridized to a pBH600-derived probe. These two trimethoprim resistance genes appear novel. The gene on plasmid pBH700 codes for an enzyme that seems widespread among S. sonnei isolates in the USA.

Trans retinoic acid enhances the growth response of epidermal keratinocytes to epidermal growth factor and transforming growth factor beta

Retinoids have been shown to either stimulate or inhibit epidermal keratinocyte proliferation. We have observed that in serum and growth factor free medium (basal medium), epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) stimulated DNA synthesis in mouse epidermal keratinocyte cultures (mKC) in a time- and dose-dependent manner. Incubation with all-trans retinoic acid (RA) greatly enhanced the stimulatory effect of EGF. Transforming growth factor beta (TGF beta) inhibited the EGF-induced DNA synthesis in a dose-dependent manner, and the inhibition was greatly enhanced by a low dose of RA. Treatment of growth-factor deprived human keratinocyte cultures (hKC) with RA before incubation in basal medium containing EGF or a mixture of EGF, bovine pituitary extract (BPE), and insulin caused a dose-related increase in DNA synthesis and cell growth (cell number), respectively. A low concentration of RA also enhanced the inhibitory effect of TGF beta on growth-factor-induced DNA synthesis and cell growth in hKC. These findings suggest that the differential effects of retinoids on epidermal keratinocyte proliferation are in part due to an enhancement of the response of keratinocytes to positive and negative peptide growth factors.

Prostaglandin F2 alpha effects on intraocular pressure negatively correlate with FP-receptor stimulation

According to the current working classification for prostanoid receptors, the prostaglandin F2 alpha-sensitive receptor (FP-receptor) may be identified by comparing the rank order of activity of prostaglandin F2 alpha (PGF2 alpha) and its analogues. In order to further understand the pharmacology of PGF2 alpha-induced ocular hypotension, the intraocular pressure response to PGF2 alpha and selected analogues was compared with their rank order of activity in typical FP-receptor preparations such as contraction of the cat iris sphincter and affinity for corporal luteal membrane binding sites. The rank order of potency for decreasing intraocular pressure was as follows: PGF2 alpha greater than PGF1 alpha greater than 16-phenoxytetranor PGF2 alpha greater than 17-phenyltrinor PGF2 alpha = fluprostenol (inactive). For cat iris sphincter contraction, the rank order of potency appears to be fluprostenol = 17-phenyltrinor PGF2 alpha greater than 16-phenoxytetranor PGF2 alpha = PGF2 alpha greater than PGF1 alpha. The rank order of potency for PGF2 alpha analogues in decreasing intraocular pressure appears to negatively correlate with the rank order for cat iris sphincter contraction and literature values for corporal luteal membrane binding. It is concluded that the ocular hypotensive effect of PGF2 alpha is not mediated by the FP-receptor.

Preferential inhibition of 5-lipoxygenase activity by manoalide

Treatment of human polymorphonuclear leukocytes (PMNLs) with micromolar concentrations of the anti-inflammatory drug manoalide inhibited production of leukotriene B4 (LTB4) and LTC4/LTD4 in response to the calcium ionophore A23187. In an attempt to further define the mechanism(s) of action of this agent, we have examined its interaction with several lipoxygenase enzymes. In RBL-1 cells, manoalide inhibited 5-lipoxygenase (5-LO) activity with an approximate IC50 of 0.3 microM. This was equipotent in our system with the known lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA). Manoalide was virtually inactive, however, against 12-lipoxygenase activity in both human platelets and mouse epidermis, with little inhibition seen at concentrations up to 100 microM. Manoalide showed some activity against soybean lipoxygenase, although it was 30- to 50-fold less potent than as an inhibitor of the 5-lipoxygenase enzyme. These data indicate that manoalide is a selective 5-LO inhibitor and suggest the possibility that its anti-inflammatory actions may be due, at least in part, to inhibition of leukotriene synthesis.