Direct, real-time, simultaneous monitoring of intravitreal nitric oxide and oxygen in endotoxin-induced uveitis in rabbits

Cationic Nano-Lipidic Carrier Mediated Ocular Delivery of Triamcinolone Acetonide: A Preclinical Investigation in the Management of Uveitis

The current study was undertaken to evaluate the efficacy of a novel nano-lipoidal eye drop formulation of triamcinolone acetonide (TA) for the topical treatment of uveitis. The triamcinolone acetonide-loaded nanostructured lipid carriers (cTA-NLC) were developed by employing 'hot microemulsion method' using biocompatible lipids, which exhibited a sustained release nature and enhanced efficacy when evaluated in vitro. The in vivo efficacy of this developed formulation was tested on Wistar rats, and a single-dose pharmacokinetic study was conducted in rabbits. The eyes of animals were examined for any signs of inflammation using the 'Slit-lamp microscopic' method. The aqueous humor collected from the sacrificed rats was tested for total protein count and cell count. The total protein count was determined using BSA assay method, while the total cell count was determined by Neubaur's hemocytometer method. The results showed that the cTA-NLC formulation had negligible signs of inflammation, with a clinical score of uveitis 0.82 ± 0.166, which is much less than control/untreated (3.80 ± 0.3) and free drug suspension (2.66 ± 0.405). The total cell count was also found to be significantly low for cTA-NLC (8.73 ± 1.79 × 10⁵) as compared to control (52.4 ± 7.71 × 10⁵) and free drug suspension (30.13 ± 3.021 × 10⁵). Conclusively, the animal studies conducted showed that our developed formulation holds the potential for effective management of uveitis.

A thermo-sensitive, injectable and biodegradable in situ hydrogel as a potential formulation for uveitis treatment

The thermo-sensitive hydrogels with high drug loading rate achieved sustained drug release over 2 weeks. Histopathological examination of retina confirmed the excellent biocompatibility and effective anti-inflammatory property of the hydrogel.

Hyperbaric oxygen reduces inflammation, oxygenates injured muscle, and regenerates skeletal muscle via macrophage and satellite cell activation

Hyperbaric oxygen treatment (HBO) promotes rapid recovery from soft tissue injuries. However, the healing mechanism is unclear. Here we assessed the effects of HBO on contused calf muscles in a rat skeletal muscle injury model. An experimental HBO chamber was developed and rats were treated with 100% oxygen, 2.5 atmospheres absolute for 2 h/day after injury. HBO reduced early lower limb volume and muscle wet weight in contused muscles, and promoted muscle isometric strength 7 days after injury. HBO suppressed the elevation of circulating macrophages in the acute phase and then accelerated macrophage invasion into the contused muscle. This environment also increased the number of proliferating and differentiating satellite cells and the amount of regenerated muscle fibers. In the early phase after injury, HBO stimulated the IL-6/STAT3 pathway in contused muscles. Our results demonstrate that HBO has a dual role in decreasing inflammation and accelerating myogenesis in muscle contusion injuries.

Lipoic acid lessens Th1-mediated inflammation in lipopolysaccharide-induced uveitis reducing selectively Th1 lymphocytes-related cytokines release

Inflammation results in the production of free radicals. We evaluated the anti-inflammatory and antioxidant capacity of lipoic acid in an experimental uveitis model upon a subcutaneous injection of endotoxin into Lewis rats. The role of oxidative stress in the endotoxin-induced uveitis model is well-known. Besides, the Th1 response classically performs a central part in the immunopathological process of experimental autoimmune uveitis. Exogenous sources of lipoic acid have been shown to exhibit antioxidant and anti-inflammatory properties. Our results show that lipoic acid treatment plays a preventive role in endotoxin-induced oxidative stress at 24 h post-administration and reduced Th1 lymphocytes-related cytokines by approximately 50-60%. Simultaneously, lipoic acid treatment caused a significant reduction in uveal histopathological grading and in the protein concentration in aqueous humors, but not in cellular infiltration.

Real-time in vivo simultaneous measurements of nitric oxide and oxygen using an amperometric dual microsensor

This paper reports a real-time study of the codynamical changes in the release of endogenous nitric oxide (NO) and oxygen (O(2)) consumption in a rat neocortex in vivo upon electrical stimulation using an amperometric NO/O(2) dual microsensor. Electrical stimulation induced transient cerebral hypoxia due to the increased metabolic demands that were not met by the blood volume inside the stimulated cortical region. A NO/O(2) dual microsensor was successfully used to monitor the pair of real-time dynamic changes in the tissue NO and O(2) contents. At the onset of electrical stimulation, there was an immediate decrease in the cortical tissue O(2) followed by a subsequent increase in the cortical tissue NO content. The averages of the maximum normalized concentration changes induced by the stimulation were a 0.41 (±0.04)-fold decrease in the O(2) and a 3.6 (±0.9)-fold increase in the NO concentrations when compared with the corresponding normalized basal levels. The peak increase in NO was always preceded by the peak decrease in O(2) in all animals (n = 11). The delay between the maximum decrease in O(2) and the maximum increase in NO varied from 3.1 to 54.8 s. This rather wide variation in the temporal associations was presumably attributed to the sparse distribution of NOS-containing neurons and the individual animal's differences in brain vasculatures, which suggests that a sensor with fine spatial resolution is needed to measure the location-specific real-time NO and O(2) contents. In summary, the developed NO/O(2) dual microsensor is effective for measuring the NO and O(2) contents in vivo. This study provides direct support for the dynamic role of NO in regulating the cerebral hemodynamics, particularly related to the tissue oxygenation.

Effects of a calcium-channel blocker (CV159) on hepatic ischemia/reperfusion injury in rats: evaluation with selective NO/pO2 electrodes and an electron paramagnetic resonance spin-trapping method

Nitric oxide (NO) and the partial pressure of oxygen (pO(2)) in the liver were simultaneously quantified in rats with partial hepatic ischemia/reperfusion injury (PHIRI). Real-time NO/pO(2) monitoring and immunohistochemical analysis for superoxide dismutase and inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) were performed to evaluate the protective effects of a dihydropyridine-type calcium-channel blocker--CV159--on PHIRI. Serum high-mobility-group box-1 (HMGB-1) was measured to assess cellular necrosis. Moreover, we used in vitro/ex vivo electron paramagnetic resonance spin trapping to assess the hydroxyl radical (*OH)-scavenging activity (OHSA) of CV159 and the liver tissue. The NO levels were significantly higher in CV159-treated rats than in control rats throughout the ischemic phase. Immediately after reperfusion, the levels temporarily increased in waves and then gradually decreased in the treated rats but remained constant in the control rats. pO(2) was continually higher in the treated rats. In these rats, hepatic eNOS expression increased, whereas iNOS expression decreased. The treated rats exhibited significantly higher cytosolic and mitochondrial concentrations NOx (NO(2)+NO(3)). The serum HMGB-1 levels significantly decreased in the treated rats. Moreover, CV159 directly scavenged *OH and both mitochondrial and cytosolic OHSA were preserved in the treated rats. Thus, CV159-mediated inhibition of intracellular Ca(2+) overloading may effectively minimize organ damage and also have *OH-scavenging activity and the cytoprotective effects of eNOS-derived NO.

Vascular dysfunction in retinopathy-an emerging role for arginase

Retinal neovascularization is a leading cause of visual disability. Retinal diseases involving neovascularization all follow the same progression, beginning with vascular inflammatory reactions and injury of the vascular endothelium and ending with neovascularization, fibrosis and retinal detachment. Understanding the mechanisms underlying this process is critical for its prevention and treatment. Research using retinopathy models has revealed that the NOX2 NADPH oxidase has a key role in inducing production of reactive oxygen species and angiogenic cytokines and causing vascular inflammatory reactions and neovascularization. This prospective review addresses the potential role of the urea/ornithine pathway enzyme arginase in this process. Studies of peripheral vessels isolated from diabetic animals have shown that increased arginase activity causes vascular endothelial cell dysfunction by decreasing availability of l-arginine to endothelial cell nitric oxide synthase which decreases nitric oxide bioavailability and increases oxidative stress. Increasing arginase activity also increases formation of polyamines and proline, which can induce cell growth and fibrosis. Studies in models of retinopathy show that increases in oxidative stress and signs of vascular inflammation are correlated with increases in arginase activity and arginase 1 expression and that decreasing arginase expression or inhibiting its activity blocks these effects. Furthermore, the induction of arginase during retinopathy is blocked by knocking out NOX2 or inhibiting NADPH oxidase activity. These observations suggest that NADPH oxidase-induced activation of the arginase pathway has a key role in causing retinal vascular dysfunction during retinopathy. Limiting the actions of arginase could provide a new strategy for treating this potentially blinding condition.

Peroxynitrite affects lidocaine by acting on membrane-constituting lipids

Inflammation frequently decreases local anesthetic effects, especially in dental anesthesia in patients with pulpitis and periodontitis. The pharmacokinetics and the mode of action of local anesthetics are closely associated with the hydrophobic interactions between these drugs and lipid bilayers that change the membrane physicochemical property, fluidity. A lipid oxidant, peroxynitrite, is produced by inflammatory cells, and it may act on nerve cell membranes and affect anesthetic efficacy. With respect to this speculated action, we addressed whether peroxynitrite acted on membrane-constituting lipids to decrease the membrane interactivity of lidocaine. Membrane fluidity changes were determined by measuring the fluorescence polarization of liposomes prepared with different phospholipids. Peroxynitrite (0.1-50 microM) rigidified nerve-cell model membranes consisting of unsaturated phospholipids, as well as liposomal membranes consisting of 1,2-dioleoylphosphatidylcholine and 1-stearoyl-2-arachidonylphosphatidylcholine, but peroxynitrite did not rigidify 1, 2-dipalmitoylphosphatidylcholine liposomal membranes. The pretreatment of nerve-cell model membranes with peroxynitrite (0.1-50 microM) decreased the membrane-fluidizing effects of lidocaine (5.0 mg x ml(-1)) to 63%-86% of the control (not treated with peroxynitrite) depending on the peroxynitrite concentration. As one of the mechanisms of the local anesthetic failure associated with inflammation, inflammatory peroxynitrite may affect local anesthesia by acting on membrane-constituting unsaturated phospholipids.

Membrane effect of lidocaine is inhibited by interaction with peroxynitrite

Inflammation is clinically well known to decrease the efficiency of local anesthesia, an effect which has been explained mechanistically by tissue acidosis in the literature. However, recent studies offer no support to such a pharmacopathological background for anesthetic failure. Because inflammatory cells produce significant amounts of peroxynitrite, the peroxynitrite could interact with local anesthetics to decrease their effects. To examine this speculated interaction, we determined whether membrane fluidization, as one mode of local anesthetic action, was influenced by peroxynitrite. The membrane effects were analyzed by measuring the fluorescence polarization of liposomes prepared with 1, 2-dipalmitoylphosphatidylcholine. Although lidocaine, at a clinically relevant concentration, fluidized liposomal membranes, its fluidizing potency was reduced to 43.6 +/- 4.4% and 58.4 +/- 7.5% of that in membranes without peroxynitrite when membranes were pretreated with 50 and 250 microM peroxynitrite, respectively, for 15 min. A significant inhibition of membrane fluidization of 27.5 +/- 6.8%, was also observed after reaction for 5 min. Peroxynitrite released by inflammatory cells may affect local anesthesia through a possible interaction with lidocaine, inhibiting its membrane-fluidizing effect.