Surya P. Ayalasomayajula

Celecoxib, a selective cyclooxygenase-2 inhibitor, inhibits retinal vascular endothelial growth factor expression and vascular leakage in a streptozotocin-induced diabetic rat model

Overexpression of vascular endothelial growth factor (VEGF) is implicated in the development of vascular leakage and retinal neovascularization in diabetic subjects. The objective of this study was to determine whether celecoxib, a selective cyclooxygenase-2 enzyme inhibitor, reaches ocular tissues following oral administration and inhibits the retinal VEGF expression and vascular leakage in a streptozotocin-induced diabetic rat model. After administering a single intraperitoneal injection of streptozotocin (60 mg/kg) to Sprague-Dawley rats and ensuring the induction of diabetes at the end of 24 h, celecoxib was administered b.i.d. by oral gavage (50 mg/kg). On day 8, the animals were sacrificed and the retinal VEGF and cyclooxygenase-2 mRNA levels, ocular tissue celecoxib concentrations, and the vitreous/plasma protein ratio were determined. In diabetic rats, the retinal VEGF mRNA expression was 2.3-fold compared to controls, with a corresponding increase in cyclooxygenase-2 mRNA expression. Celecoxib treatment inhibited VEGF mRNA expression without any significant reduction in cyclooxygenase-2 mRNA. Furthermore, the retinal vascular leakage estimated as vitreous to plasma protein ratio increased in diabetic animals from 0.35+/-0.1 to 1.1+/-0.1 and celecoxib treatment significantly decreased this ratio to 0.4+/-0.1. Celecoxib levels were 24.8+/-6.6, 1.9+/-1, 1.7+/-0.8, and 6.9+/-0.9 ng/mg in the retina, vitreous, lens, and cornea, respectively. The plasma celecoxib levels were 85+/-24 ng/ml. Thus, celecoxib reaches the retina after oral administration and reduces diabetes-induced retinal VEGF mRNA expression and vascular leakage by inhibiting the activity of cyclooxygenase-2 enzyme.

Retinal Delivery of Celecoxib Is Several-Fold Higher Following Subconjunctival Administration Compared to Systemic Administration

AbstractPurpose. We have previously demonstrated that celecoxib, a selective COX-2 inhibitor, reaches the retina following repeated oral administrations and inhibits diabetes-induced vascular endothelial growth factor (VEGF) mRNA expression and vascular leakage in a rat model. The aim of this study was to quantify the relative retinal bioavailability of celecoxib from the subconjunctival route compared to a systemic route. Methods. The plasma and ocular tissue distribution of celecoxib was determined in male Sprague-Dawley rats following subconjunctival and intraperitoneal administrations of drug suspension at a dose of 3 mg/rat. The animals were sacrificed at 0.5, 1, 2, 3, 4, 8, and 12 h post-dosing, the blood was collected, and the eyes were enucleated and frozen. The plasma, sclera, retina, vitreous, lens, and the cornea were isolated and celecoxib levels were determined using an HPLC method. The tissue exposure of the drug was measured as the area under the curve (AUC0-≈) of the concentration vs. time profiles. The relative bioavailability was estimated as the AUC0-≈ ratio between subconjunctival and intraperitoneal groups. Results. For the subconjunctivally dosed (ipsilateral) eye, the AUC0-≈ ratios between subconjunctival and intraperitoneal groups were 0.8 ± 0.1, 53 ± 4, 54 ± 8, 145 ± 21, 61 ± 16, and 52 ± 6 for plasma, sclera, retina, vitreous, lens, and cornea, respectively. For the contralateral ocular tissues, the AUC0-≈ ratios were 1.2 ± 0.3, 1.1 ± 0.3, 1.1 ± 0.4, 1.0 ± 0.3, and 1.2 ± 0.3 in the sclera, retina, vitreous, lens, and the cornea, respectively, between the subconjunctival and the intraperitoneal groups. Assuming that the drug AUCs in contralateral eye were equal to the systemic pathway contribution to AUCs in the ipsilateral eye, the percent contribution of local pathways as opposed to systemic circulation for celecoxib delivery to the ipsilateral eye tissues was estimated to be 98% or greater. Conclusions. The retinal delivery of celecoxib was substantially higher following subconjunctival administration compared to the intraperitoneal route. The transscleral pathway almost completely accounts for the retinal celecoxib delivery following subconjunctival administration.

Nanoparticle formulation enhances the delivery and activity of a vascular endothelial growth factor antisense oligonucleotide in human retinal pigment epithelial cells

The objective of this study was to investigate the delivery and activity of a vascular endothelial growth factor (VEGF) antisense oligonucleotide in a human retinal pigment epithelial cell line (ARPE‐19) using a biodegradable nanoparticulate delivery system. A 19‐mer antisense phosphorothioate oligonucleotide (PS‐ODN) complementary to bases 6–24 relative to the translational start site of the VEGF mRNA, a sense PS‐ODN and a mismatch PS‐ODN were examined for the inhibition of secretion and mRNA expression of VEGF using an enzyme‐linked immunosorbent assay and reverse transcription–polymerase chain reaction, respectively. Nanoparticles of the antisense oligonucleotides were formulated using a poly(lactide‐co‐glycolide) (50:50) copolymer using a double emulsion solvent evaporation method. After preparing nanoparticles, drug loading, encapsulation efficiency and particle size were determined. The cells were exposed to either plain solution of oligonucleotide or nanoparticles of oligonucleotide from Day 3 through Day 6. Alternatively, the cells were incubated with PS‐ODNs and lipofectin for 4h on Day 4. In all studies, VEGF secretion and mRNA expression were determined on Day 6. The particle size, drug loading and encapsulation efficiency were 252 nm, 5.5% and 16.5%, respectively. The antisense PS‐ODN inhibited VEGF mRNA and protein secretion when delivered using nanoparticles or lipofectin but not in its free form. This was consistent with the ability of nanoparticles and lipofectin to elevate the cellular uptake of the oligonucleotide by 4‐fold and 13‐fold, respectively. Neither mismatch nor sense oligonucleotides inhibited VEGF secretion. In conclusion, biodegradable nanoparticles enhance cellular delivery of a VEGF antisense oligonucleotide and inhibit VEGF secretion and mRNA expression in a human retinal pigment epithelial cell line.

Induction of vascular endothelial growth factor by 4-hydroxynonenal and its prevention by glutathione precursors in retinal pigment epithelial cells

Although 4-hydroxynonenal, a highly reactive lipid peroxidation product, is implicated in several age-related disorders such as Alzheimers and Parkinsons diseases, its role in age-related macular degeneration is not known. The purpose of this study was to determine whether 4-hydroxynonenal increases vascular endothelial growth factor (VEGF) expression in human retinal pigment epithelial cells (ARPE-19), a source of VEGF in choroidal neovascularization observed in age-related macular degeneration. In addition, it was the purpose of this study to assess whether glutathione (GSH) and GSH precursors can inhibit the effects of 4-hydroxynonenal. At 1 micro M, 4-hydroxynonenal did not alter cell viability, but elevated VEGF secretion and mRNA expression by 35% (p<0.05) and 1.9-fold (p<0.05), respectively. However, at concentrations 5 microM and above, 4-hydroxynonenal reduced VEGF secretion as well as cell viability. At 1 and 10 microM, 4-hydroxynonenal did not induce apoptosis in ARPE-19 cells. 4-Hydroxynonenal (1 microM) reduced intracellular GSH by 25% (p<0.05) and increased oxidative stress by 50% (p<0.05). GSH precursor pretreatment for 1 h, which increased intracellular GSH levels by 50% (p<0.05), as well as GSH co-treatment, inhibited the VEGF-inductive and cytotoxic effects of 4-hydroxynonenal. Thus, 4-hydroxynonenal (1 microM) induces VEGF expression and secretion in ARPE-19 cells. This effect is likely due to GSH depletion and an associated increase in intracellular oxidative stress, resulting in increased VEGF mRNA levels. 4-Hydroxynonenal-mediated VEGF secretion as well as cytotoxicity can be reversed with GSH precursor pretreatment or GSH co-treatment.

A Biodegradable Injectable Implant Sustains Systemic and Ocular Delivery of an Aldose Reductase Inhibitor and Ameliorates Biochemical Changes in a Galactose-Fed Rat Model for Diabetic Complications

AbstractPurpose. To fabricate and characterize in vitro and in vivo performance of a sustained release biodegradable implant for N-4-(benzoylaminophenylsulfonyl glycine) (BAPSG), a novel aldose reductase inhibitor. Methods. The ability of BAPSG to inhibit aldose reductase activity and glucose-induced vascular endothelial growth factor (VEGF) expression was assessed in a retinal pigment epithelial cell line (ARPE-19). A poly (DL-lactic-co-glycolic acid) implant containing 50% w/w BAPSG was fabricated and characterized for drug loading, in vitro drug release, and the thermal behavior of the drug and the polymer. Implants were injected subcutaneously into a galactose-fed diabetic rat model and cataract scores, plasma and tissue drug levels, galactitol levels in the lens and the retina, glutathione levels in the plasma, lens, cornea and retina and VEGF expression in the retina were determined on or until 18 days. Results. BAPSG inhibited aldose reductase activity and reduced VEGF expression in ARPE-19 cells. Implants (1 × 4 mm), with a loading efficiency of 106 ∓ 7% for BAPSG, were fabricated. Upon implant fabrication, while the glass transition temperature of the polymer decreased, the melting point of the drug was not affected. In vivo drug release correlated well with in vitro release, with ≈44% drug release occurring in vivo by the end of 18 days. The implant reduced galactitol accumulation, glutathione depletion, cataract scores, and VEGF expression in galactose-fed rats. Conclusions. An injectable biodegradable implant of BAPSG sustained drug release in vitro and in vivo, and reduced galactitol accumulation, glutathione depletion, cataract scores, and VEGF expression in galactose-fed rats.

Fluocinolone Inhibits VEGF Expression via Glucocorticoid Receptor in Human Retinal Pigment Epithelial (ARPE-19) Cells and TNF-α-Induced Angiogenesis in Chick Chorioallantoic Membrane (CAM)

PURPOSE The purpose of this study was to determine whether fluocinolone inhibits vascular endothelial growth factor (VEGF) expression in a retinal pigment epithelial cell line (ARPE-19) and TNF-alpha-induced angiogenesis in chick chorioallantoic membrane (CAM) assay. METHODS The dose-dependent effect of fluocinolone (0.0001-1 microM) on VEGF secretion, VEGF mRNA expression, and cytotoxicity was determined in confluent monolayers of ARPE-19 cells using ELISA, RT-PCR, and MTT assay, respectively. The effect of a glucocorticoid receptor antagonist (RU486) on fluocinolone-mediated VEGF expression was determined. The effect of fluocinolone in inhibiting TNF-alpha-induced angiogenesis was determined using chick chorioallantoic membrane (CAM) assay. The dose-dependent effect of fluocinolone (0.0001-1 microM) in inhibiting 1% serum-stimulated ARPE-19 cell proliferation was determined using BrdU labeling assay. RESULTS At concentrations devoid of cytotoxicity, fluocinolone inhibited VEGF secretion as well as mRNA expression in ARPE-19 cells. RU486 (1 microM) treatment prevented inhibition of VEGF secretion and VEGF mRNA expression by fluocinolone (0.1 microM). Fluocinolone (50 ng/egg) inhibited angiogenesis induced by TNF-alpha. The ARPE-19 cell proliferation was inhibited by fluocinolone in a dose-dependent manner. CONCLUSIONS Fluocinolone inhibited VEGF expression in ARPE-19 cells via its glucocorticoid receptor activity. In addition, fluocinolone inhibited proliferation of ARPE-19 cells and TNF-alpha-induced angiogenesis in chorioallantoic membranes.

Intratracheal budesonide-poly(lactide-co-glycolide) microparticles reduce oxidative stress, VEGF expression, and vascular leakage in a benzo(a)pyrene-fed mouse model

The purpose of this study was to determine whether intratracheally instilled polymeric budesonide microparticles could sustain lung budesonide levels for one week and inhibit early biochemical changes associated with benzo(a)pyrene (B[a]P) feeding in a mouse model for lung tumours. Polymeric microparticles of budesonide‐poly (dl‐lactide‐co‐glycolide) (PLGA 50:50) were prepared using a solvent evaporation technique and characterized for their size, morphology, encapsulation efficiency, and in‐vitro release. The microparticles were administered intratracheally (i.t.) to B[a]P‐fed A/J mice. At the end of one week drug levels in the lung tissue and bronchoalveolar lavage (BAL) were estimated using HPLC and compared with systemic (intramuscular) administration. In addition, in‐vivo end points including malondialdehyde (MDA), glutathione (GSH), total protein levels and vascular endothelial growth factor (VEGF) in BAL, and VEGF and c‐myc mRNA levels in the lung tissue were assessed at the end of one week following intratracheal administration of budesonide microparticles. Budesonide‐PLGA microparticles (1–2 μm), with a budesonide loading efficiency of 69–94%, sustained in‐vitro budesonide release for over 21 days. Compared with the intramuscular route, intratracheally administered budesonide‐PLGA microparticles resulted in higher budesonide levels in the BAL and lung tissue. In‐vivo, B[a]P‐feeding increased BAL MDA, lung VEGF mRNA, lung c‐myc mRNA, BAL total protein, and BAL VEGF levels by 60, 112, 71, 154, and 78%, respectively, and decreased BAL GSH by 62%. Interestingly, intratracheally administered budesonide‐PLGA particles inhibited these biochemical changes. Thus, biodegradable budesonide microparticles sustained budesonide release and reduced MDA accumulation, GSH depletion, vascular leakage, and VEGF and c‐myc expression in B[a]P‐fed mice, indicating the potential of locally delivered sustained‐release particles for inhibiting angiogenic factors in lung cancer.

Assessment of Drug Interaction Potential between LCZ696, an Angiotensin Receptor Neprilysin Inhibitor, and Digoxin or Warfa rin

LCZ696 (sacubitril/valsartan) is a first-in-class angiotensin receptor neprilysin inhibitor that simultaneously inhibits neprilysin and blocks the angiotensin II receptor. LCZ696 has been recently approved for treatment of HF and likely be co-administered with digoxin or warfarin. The drug interaction potential between LCZ696 and digoxin or warfarin was evaluated because of their potentially shared metabolic/elimination pathways. Two separate drug-drug interaction studies were conducted in healthy subjects: LCZ696 200 mg twice daily was co-administered with digoxin 0.25 mg once daily (n=24) and warfarin 25 mg single dose (n=26), respectively. The pharmacokinetic profiles of the LCZ696 analytes (sacubitril, LBQ657 and valsartan), digoxin and R- and S-warfarin, the pharmacodynamic effects of warfarin and the safety and tolerability of the investigational drugs were assessed. The geometric mean ratio (GMR) and 90%confidence interval (90% CI) for Cmax and AUCs of R- and S-warfarin, digoxin, and pharmacologically active LCZ696 analytes were within the bioequivalence range of 0.8-1.25 when co-administered. The GMR and 90% CI of warfarin pharmacodynamics effects were also within 0.8-1.25 range when co-administered with LCZ696. LCZ696 was generally safe and welltolerated when administered alone or in combination with digoxin/warfarin. No drug-drug interaction was observed upon co-administration of LCZ696 with digoxin/warfarin in healthy subjects.

Probenecid treatment enhances retinal and brain delivery of N-4-benzoylaminophenylsulfonylglycine: An anionic aldose reductase inhibitor

Anion efflux transporters are expected to minimize target tissue delivery of N-[4-(benzoylaminophenyl)sulfonyl]glycine (BAPSG), a novel carboxylic acid aldose reductase inhibitor, which exists as a monocarboxylate anion at physiological conditions. Therefore, the objective of this study was to determine whether BAPSG delivery to various eye tissues including the retina and the brain can be enhanced by probenecid, a competitive inhibitor of anion transporters. To determine the influence of probenecid on eye and brain distribution of BAPSG, probenecid was administered intraperitoneally (120 mg/kg body weight; i.p.) 20 min prior to BAPSG (50 mg/kg; i.p.) administration. Drug disposition in various eye tissues including the retina and the brain was determined at 15 min, 1, 2 and 4h after BAPSG dose in male Sprauge-Dawley rats. To determine whether probenecid alters plasma clearance of BAPSG, influence of probenecid (120 mg/kg; i.p.) on the plasma pharmacokinetics of intravenously administered BAPSG (15 mg/kg) was studied as well. Finally, the effect of probenecid co-administration on the ocular tissue distribution of BAPSG was assessed in rabbits following topical (eye drop) administration. Following pretreatment with probenecid in the rat study, retinal delivery at 1h was increased by about 11-fold (2580 ng/g vs. 244 ng/g; p<0.05). Further, following probenecid pretreatment, significant BAPSG levels were detectable in the brain (45 + or - 20 ng/g) at 1h, unlike controls where the drug was not detectable. Plasma concentrations, plasma elimination half-life, and total body clearance of intravenously administered BAPSG were not altered by i.p. probenecid pretreatment. In the topical dosing study, a significant decline in BAPSG delivery was observed in the iris-ciliary body but no significant changes were observed in other tissues of the anterior segment of the eye including tears. Thus, inhibition of anion transporters is a useful approach to elevate retinal and brain delivery of BAPSG.