Topical Ocular TRPV1 Antagonist SAF312 (Libvatrep) for Postoperative Pain After Photorefractive Keratectomy.

Purpose: Evaluation of safety and efficacy of topical ocular SAF312 (Libvatrep) in post-photorefractive keratectomy (PRK) pain. Methods: In this placebo (vehicle)-controlled, participant- and investigator-masked study, 40 participants were randomized (1:1) to two treatment sequences in a bilateral PRK crossover design (SAF312 2.5% followed by vehicle [or vice versa], one eye drop, four times daily for 72 hours after PRK). Primary endpoints were visual analog scale (VAS) pain scores at 6 hours after first drop of study drug and average VAS scores over 0 to 12 hours postoperatively. Secondary endpoints included postoperative oral rescue medication (ORM) use and adverse events (AEs). Results: All 40 participants completed the study. Both primary endpoints were met; mean difference in VAS pain scores between SAF312- and vehicle-treated eyes was -11.13 (P = 0.005, -25%) at 6 hours postoperatively and -8.56 (P = 0.017, -22%) over 0 to 12 hours. Mean VAS pain scores with SAF312 were consistently lower than with vehicle from 1 hour postoperatively up to 30 hours (P ≤ 0.10 observed in 8/11 time points). Less ORM was taken with SAF312 up to 0 to 72 hours postoperatively, with a trend of fewer participants taking ORM at 0 to 24 hours postoperatively with SAF312 versus vehicle. No serious AEs were reported. All ocular AEs were mild and transient, and none were drug related. SAF312-treated eyes showed no delay in wound healing and had a lower grade 4 conjunctival hyperemia 24 hours postoperatively versus vehicle-treated eyes. Conclusions: SAF312 was well tolerated and effective in reducing ocular pain post-PRK. Translational Relevance: Topical SAF312 presents a new therapeutic option for patients undergoing PRK.

Acute tobacco smoke exposure promotes mitochondrial permeability transition in rat heart.

Chronic exposure to tobacco smoke is known to impair mitochondrial function. However, the effect of acute tobacco smoke exposure (ATSE) in vivo, as might occur in social settings, on mitochondrial function and calcium handling of cardiac cells has not been examined. It was hypothesized that ATSE might adversely modify mitochondrial function as reflected in mitochondrial energetics, membrane potential, and calcium transport. Mitochondria were isolated from the hearts of adult rats either exposed to 6 h of environmental tobacco smoke ( approximately 60 mg/mm3 tobacco smoke particles) or sham exposure. To model a calcium stress similar to ischemia/reperfusion, mitochondria were exposed to a Ca2+ bolus with measurement of membrane potential, energetics, Ca2+uptake and release, and redox state. ATSE mitochondria were characterized by significantly higher ADP-stimulated ATP production and a more reduced redox state (NADH ratio) under basal conditions without observed changes in resting Psim. Exposure of ATSE mitochondria to Ca2+stress resulted in significantly more rapid depolarization of Psim. The initial rate of Ca2+uptake was not altered in ATSE mitochondria, but CsA-sensitive Ca2+ release was significantly increased. ATSE does not significantly alter resting mitochondrial function. However, ATSE modifies the response of cardiac mitochondria to calcium stress, resulting in a more rapid depolarization and subsequent release of Ca2+ via the mitochondrial permeability transition (MPT).

Sevoflurane preconditioning limits intracellular/mitochondrial Ca2+ in ischemic newborn myocardium.

UNLABELLED: Sevoflurane preconditioning (SPC) in adult hearts reduces myocardial ischemia/reperfusion (I/R) injury, an effect that may be mediated by reductions in intracellular Ca(2+) ([Ca(2+)](i)) and/or mitochondrial Ca(2+) ([Ca(2+)](m)) accumulation during ischemia and reperfusion. Because the physiology, pharmacology, and metabolic responses of the newborn differ from adults, we tested the hypothesis that SPC protects newborn myocardium by limiting [Ca(2+)](i) and [Ca(2+)](m) by a K(ATP) channel-dependent mechanism. Fluorescence spectrofluorometry and nuclear magnetic resonance spectroscopy were used to measure [Ca(2+)](i), [Ca(2+)](m), and adenosine triphosphate (ATP) in 4- to 7-day-old Langendorff-perfused rabbit hearts. Three experimental groups were used to study the effect of SPC on [Ca(2+)](m)/[Ca(2+)](i), ATP, as well as hemodynamics and ischemic injury. The role of mitochondrial K(ATP) channels was assessed by exposing the SPC hearts to the mitochondrial K(ATP) channel blocker 5-hydroxydecanoic acid. Our results show that SPC significantly decreased [Ca(2+)](i) and [Ca(2+)](m) during I/R, as well as decreased creatine kinase release during reperfusion and resulted in higher ATP. 5-Hydroxydecanoic acid abolished the effect of SPC on [Ca(2+)], hemodynamics, ATP, and creatine kinase release. In conclusion, decreased [Ca(2+)](i) and [Ca(2+)](m) observed with SPC is associated with greater ATP recovery as well as diminished cell injury. Mitochondrial K(ATP) channel blockade attenuates the SPC effect during I/R, suggesting that these channels are involved in the protective effects of SPC in the newborn. IMPLICATIONS: The results of this study support the hypothesis that sevoflurane preconditioning protects newborn hearts from calcium overload and ischemic injury via a mechanism dependent on mitochondrial KATP channels.

Ischemic preconditioning and diazoxide limit mitochondrial Ca overload during ischemia/reperfusion: Role of reactive oxygen species.

BACKGROUND: Generation of reactive oxygen species (ROS) is associated with cardioprotection imparted by ischemic preconditioning (IPC) and pharmacological PC (PPC). The authors have previously shown that IPC or PPC, using the mitochondrial ATP-sensitive K(+) channel opener diazoxide (DZ), reduce mitochondrial Ca(2+) ([Ca(2+)](m)) during ischemia and reperfusion. OBJECTIVES: To test the hypothesis that both IPC and PPC (using DZ) lead to reduced [Ca(2+)](m) and improved functional recovery via a ROS-dependent mechanism. METHODS: Intracellular Ca(2+) ([Ca(2+)](i)) and [Ca(2+)](m) were measured in isolated perfused rat hearts loaded with the fluorescent indicator indo-1 acetoxymethyl ester. [Ca(2+)](m) was determined by quenching the cytosolic indo-1 signal using manganese before ischemia (25 min). IPC and DZ (100 muM) group hearts were studied with and without the ROS scavenger N-2-mercaptopropionyl glycine (400 muM) (2-MPG). RESULTS: Both IPC and DZ significantly reduced [Ca(2+)](i) and [Ca(2+)](m) on reperfusion compared with the control. Administration of 2-MPG with washout before ischemia significantly attenuated the reduction in [Ca(2+)](m) observed on reperfusion in both the IPC and DZ groups. Additionally, the myocardial functional protection imparted by IPC or DZ was lost with the administration of 2-MPG. CONCLUSIONS: The [Ca(2+)](m)-reducing effect of IPC and DZ was attenuated with the administration of 2-MPG, resulting in decreased myocardial functional performance and increased release of creatine kinase, a marker of cellular injury. It can be concluded that IPC and DZ impart their protective effect via a mechanism involving ROS generation before the ischemic episode.

Gender modulation of Ca(2+) uptake in cardiac mitochondria.

BACKGROUND: Mitochondrial calcium overload is an important factor in defining ischemia/reperfusion injury. Since pre-menopausal women are relatively protected from ischemia and heart disease, we tested the hypothesis that gender differences alter Ca(2+) handling in rat cardiac mitochondria. METHODS: Using cardiac mitochondria isolated from male, female, and ovariectomized Sprague-Dawley rats, we measured mitochondrial calcium transport, redox state, and membrane potential (Deltapsi(m)) during exposure to a calcium bolus. Redox state was modulated using either succinate (S) or succinate and pyruvate (SP) as substrates. RESULTS: Net Ca(2+) uptake rates were significantly lower in female than male mitochondria using SP, substrate conditions that resulted in a lower redox state (NADH/NAD(+)). Inhibition of the mitochondrial transition pore (MTP) using cyclosporin A showed significantly lower net Ca(2+) uptake in both substrate solutions when mitochondria from female and ovariectomized animals were compared to males, a finding consistent with gender modulation of the mitochondrial uniporter. Blockade of the Ca(2+) uniporter by ruthenium red abolished gender or substrate solution differences in calcium release. While there were no significant differences in resting Deltapsi(m), or Deltapsi(m) following Ca(2+) addition, 80% of female samples recovered from Ca(2+)-induced depolarization compared to 57% and 43% of male and ovariectomized animals, respectively. CONCLUSIONS: Mitochondria from female hearts have lower Ca(2+) uptake rates under physiologic substrate solutions (succinate/pyruvate) and are able to appropriately maintain DeltaYm under conditions of high [Ca(2+)]. These differences are consistent with gender modulation of the Ca(2+) uniporter and may be a mechanism by which female myocardium suffers less injury with ischemia/reperfusion.