Qian Garrett

Role of carnitine in disease

Carnitine is a conditionally essential nutrient that plays a vital role in energy production and fatty acid metabolism. Vegetarians possess a greater bioavailability than meat eaters. Distinct deficiencies arise either from genetic mutation of carnitine transporters or in association with other disorders such as liver or kidney disease. Carnitine deficiency occurs in aberrations of carnitine regulation in disorders such as diabetes, sepsis, cardiomyopathy, malnutrition, cirrhosis, endocrine disorders and with aging. Nutritional supplementation of L-carnitine, the biologically active form of carnitine, is ameliorative for uremic patients, and can improve nerve conduction, neuropathic pain and immune function in diabetes patients while it is life-saving for patients suffering primary carnitine deficiency. Clinical application of carnitine holds much promise in a range of neural disorders such as Alzheimers disease, hepatic encephalopathy and other painful neuropathies. Topical application in dry eye offers osmoprotection and modulates immune and inflammatory responses. Carnitine has been recognized as a nutritional supplement in cardiovascular disease and there is increasing evidence that carnitine supplementation may be beneficial in treating obesity, improving glucose intolerance and total energy expenditure.

Mediation of Transforming Growth Factor-β1-Stimulated Matrix Contraction by Fibroblasts: A Role for Connective Tissue Growth Factor in Contractile Scarring

Excessive cell-mediated tissue contraction after injury can lead to morbid contractile scarring in the body. In the eye this can cause blindness because of posterior capsule opacification, proliferative vitroretinopathy, failure of glaucoma filtration surgery, and corneal haze. During repair, transforming growth factor (TGF)-beta and connective tissue growth factor (CTGF) genes are co-ordinately expressed. Although TGF-beta and CTGF stimulate new matrix deposition, their role and regulation during contractile scarring is unknown. In this study, an in vitro model of collagen matrix contraction culminating from tractional forces generated by fibroblasts showed that both TGF-beta(1) and CTGF-stimulated contraction. Using a specific anti-sense oligodeoxynucleotide to CTGF the procontractile activity of TGF-beta(1) was found to be mediated by CTGF. During contraction fibroblasts produced similar levels of matrix metalloproteinases (MMPs)-2 and -9 with TGF-beta(1) or CTGF and a modest increase in MMP-1 with CTGF only (indicated by zymography and enzyme-linked immunosorbent assay). The requirement of MMPs for contraction was demonstrated using a broad-spectrum synthetic inhibitor. This study demonstrates a new function for CTGF in mediating matrix contraction by fibroblasts involving MMPs and suggests a novel regulatory mechanism for TGF-beta-stimulated contraction. Inhibition of CTGF activity or gene transcription could be a suitable target for anti-scarring therapies.

Care regimen and lens material influence on silicone hydrogel contact lens deposition

Purpose. To quantitatively detect proteins and cholesterol extracted from worn silicone hydrogel contact lenses and determine the effect of various lens care solutions on deposit accumulation. Methods. Contact lenses, made from different polymers and worn on a daily wear schedule with different lens care solutions, were collected. Lipid and protein deposits were extracted by methanol:chloroform (1:1, v/v) and protein extraction solution (containing urea and surfactant), respectively. Lipid extracts were separated and cholesterol quantified using thin layer chromatography. Protein extracts were quantified using standard techniques. Results. Among all lenses tested, Balafilcon A lenses exhibited greatest extracted cholesterol (4.1 to 8.2 μg/lens) and total protein (5.4 to 23.2 μg/lens). AQuify was the most effective solution in reducing extracted deposits, especially extracted protein, from Balafilcon A lenses. AQuify and Opti-Free RepleniSH solutions were most effective in reducing extracted cholesterol from Senofilcon A and Galyfilcon A lenses, respectively. Use of Opti-Free Express solution resulted in more extracted protein from Lotrafilcon B lenses than use of other solutions. Generally, Lotrafilcon B, Senofilcon A, and Galyfilcon A lenses accumulated relatively low amount of proteins. Lotrafilcon B lenses accumulated the least amount of cholesterol deposit among all lenses tested regardless of solution used. Conclusions. Lens polymer (possibly associated with surface characteristics) is a prominent factor affecting lipid and protein accumulation. Within a lens polymer type, lens care solutions exhibit varying effectiveness in reducing protein and lipid accumulation.

Expression and Localization of Carnitine/Organic Cation Transporter OCTN1 and OCTN2 in Ocular Epithelium

PURPOSE The existence of an organic cation transport process in rabbit cornea and conjunctiva that mediates absorption of carnitine has previously been suggested. This study was conducted to determine the expression and localization of the carnitine/organic cation transporter (OCTN1 and OCTN2) in corneal or conjunctival epithelium. METHODS Reverse transcriptase-polymerase chain reaction (RT-PCR) was used for OCTN1 and OCTN2 mRNA expression in cultured human corneal-limbal epithelial (HCLE) or human conjunctival epithelial (HCjE) cells. Immunofluorescence staining with polyclonal antibody against human OCTN1 or OCTN2 was performed to investigate transporter expression in ocular epithelial cells or rabbit corneal and conjunctival epithelium. Polarity of the transporter expression was determined using Western blot analysis of the apical or basal membrane proteins extracted from the cultured cells. Apical or basal uptake of [H(3)]-L-carnitine was determined using the polarized epithelial cells grown onto collagen-coated porous filter support. RESULTS OCTN1 and OCTN2 mRNA expression was detected in HCLE and HCjE cells of rabbits and humans. OCTN1 and OCTN2 were predominately localized in the apical membranes of the cells. HCLE and HCjE cells were able to take up L-carnitine; most carnitine uptake occurred through the apical surfaces. CONCLUSIONS This report is the first to document OCTN1 and OCTN2 expression in human corneal and conjunctival epithelial cells. These findings suggest potential involvement of OCTN1 and OCTN2 in the transport of carnitine in ocular tissues.

Irreversible adsorption of human serum albumin to hydrogel contact lenses: a study using electron spin resonance spectroscopy

Human serum albumin (HSA) was specifically spin labelled with 4-maleimido-tempo (MSL) at its cysteine 34 residue (HSA-MSL). The irreversible adsorption of HSA-MSL to hydrogel contact lenses (etafilcon A, tefilcon and vifilcon A) was investigated using electron spin resonance (ESR) spectroscopy. Changes in ESR spectral characteristics of adsorbed HSA-MSL as compared to HSA-MSL in solution displayed an additional immobilisation of the spin label due to the adsorption. This immobilisation of MSL corresponds to a large conformational alteration of the HSA-MSL near the modified Cys 34 residue. For both etafilcon A and tefilcon, the rate of irreversible adsorption was relatively slow compared with that of vifilcon A where the maximum state of immobilisation and hence conformational change occurred within the first hour of adsorption. Furthermore, tefilcon produced markedly different ESR spectra where a strong conformational change to a less mobile protein was apparent. This supported a model where the direct irreversible adsorption of HSA from solution dominated on tefilcon as opposed to conversion of the adsorbed protein from the reversible to the irreversible state on both etafilcon A and vifilcon A. HSA-MSL adsorption onto hydrophobic poly(methylmethacrylate) (PMMA) and hydrophilic poly(N-ter-butylacrylamide) (PTBAM) latex beads was also investigated. The spin label MSL was found to be less mobile when HSA was adsorbed onto PMMA compared with PTBAM beads. It was also found that the rate of irreversible adsorption of HSA is far higher onto PMMA surfaces than onto PTBAM surfaces.

High Refractive Index Polysiloxane as Injectable, In Situ Curable Accommodating Intraocular Lens

Functionalised siloxane macromonomers, with properties designed for application as an injectable, in situ curable accommodating intraocular lens (A-IOL), were prepared via re-equilibration of a phenyl group-containing polysiloxane of very high molecular weight with octamethylcyclotetrasiloxane (D₄) and 2,4,6,8-tetra(n-propyl-3-methacrylate)-2,4,6,8-tetramethyl-cyclotetrasiloxane (D₄(AM)) in toluene using trifluoromethanesulfonic acid as a catalyst. Hexaethyldisiloxane was used as an end group to control the molecular weight of the polymer. The generated polymers had a consistency suitable for injection into the empty lens capsule. The polymers contained a low ratio of polymerisable groups so that, in the presence of a photo-initiator, they could be cured on demand in situ within 5 min under irradiation of blue light to form an intraocular lens within the lens capsule. All resulting polysiloxane soft gels had a low elastic modulus and thus should be able to restore accommodation. The pre-cure viscosity and post-cure modulus of the generated polysiloxanes were controlled by the end group and D₄(AM) concentrations respectively in the re-equilibration reactions. The refractive index could be precisely controlled by adjusting the aromatic ratio in the polymer to suit such application as an artificial lens. Lens stretching experiments with both human and non-human primate cadaver lenses of different ages refilled with polysiloxane polymers provided a significant increase in amplitude of accommodation (up to 4 D more than that of the respective natural lens). Both in vitro cytotoxicity study using L929 cell lines and in vivo biocompatibility study in rabbit models demonstrated the non-cytotoxicity and ocular biocompatibility of the polymer.

Bovine Lactoferrin Stimulates Human Corneal Epithelial Alkali Wound Healing In Vitro

PURPOSE The purpose of this study was to investigate the effect of bovine lactoferrin (BLF) on human corneal epithelial wound healing using an in vitro alkali-induced wound model and to understand its role in promoting wound healing. METHODS Confluent human corneal limbal epithelial (HCLE) cells wounded using 0.5 microL of 0.1 M sodium hydroxide were treated with BLF (0, 0.1, 1, 2.5, and 5 mg/mL) or anti-human interleukin-6 (IL-6) receptor neutralizing antibody (anti-IL-6 antibody; 1, 10, and 50 microg/mL) or tyrphostin AG1295 (an inhibitor of platelet-derived growth factor [PDGF] receptor kinase; 1 and 10 microM), IL-6, or PDGF-BB. The conditioned medium collected for BLF treatment (0 and 5 mg/mL) was analyzed using a protein array for a number of cytokines/growth factors involved in corneal wound healing. A preliminary animal study using mice was carried out to determine the effect of BLF on alkali wounds. RESULTS BLF at 2.5 and 5 mg/mL promoted wound healing (P<0.01). During wound closure, BLF upregulated PDGF-BB 180-fold and IL-6 10-fold compared with control. Treatment with tyrphostin AG1295 (10 microM; P<0.01) or anti-IL-6 antibody (50 microg/mL; P<0.01) in the presence of BLF inhibited wound closure, whereas the addition of exogenous IL-6 and PDGF-BB promoted wound closure. Preliminary animal studies have shown that BLF (5 mg/mL) promotes alkali wound healing in vivo. CONCLUSIONS These results suggest that BLF at >or=2.5 mg/mL stimulates HCLE wound healing, and this stimulation is mediated through the upregulation of PDGF or IL-6.

Carboxymethyl Cellulose Stimulates Rabbit Corneal Epithelial Wound Healing

Purpose: Previously, we reported carboxymethyl cellulose (CMC) binding to human corneal epithelial cells and promoting corneal epithelial wound closure in vitro. Using an animal model, the efficacy of CMC in promoting corneal wound healing was examined. Materials and Methods: Following corneal epithelial wounding of NZ white rabbits, CMC (0.2% or 1.0%) or control vehicle (PBS) was administered topically (4 times daily for 3 days) to wounded and unwounded eyes with or without contact lens wear. Wound healing in response to the treatments was measured as percentage reduction of fluorescein-stained wound area 0 to 72 hr post-wounding. Corneas were examined histologically and expression of zonula occludens-1 (ZO-1) tight-junction was detected by immunohistochemistry. Results: Percentage wound reduction in CMC-treated groups was significantly greater than controls (p < 0.05) at 24 and 32 hr. Complete wound closure was observed by 48 hr in 100% of CMC-treated eyes compared to 45% of vehicle-treated eyes. CMC also promoted wound closure dose-dependently. Epithelial cells formed an intact layer following CMC-treatment whereas vehicle-treated cells were less ordered. Strong ZO-1 expression in corneal epithelia of CMC-treated eyes was observed at 72 hr. Contact lens wear appeared to delay wound closure compared to without lens wear during CMC-treatment (p = 0.001). Conclusions: CMC promoted dose-dependent corneal epithelial wound healing. CMC stimulated ZO-1 expression, indicating accelerated corneal epithelial resistance barrier regeneration.

Onset time course of solution induced corneal staining

PURPOSE To evaluate the early phase time course of solution induced corneal staining. METHODS AND MATERIALS A double masked, single centred, prospective clinical trial was conducted. Twenty-five participants, either experienced or new contact lens wearers, participated in the study. Corneal staining response to short term use of ReNu MultiPlus Multipurpose Solution and PureVision silicon hydrogel contact lens with fluorescein was observed using standard techniques after 15, 30, 45, 60 and 120 min of lens wear and graded according to the IER scale. Measurements were carried out on separate days for each time point, in random order. RESULTS Mean extent of staining was greater in test than in control eyes at all time points except baseline. In test eyes, the degree of staining increased successively at each time point after insertion, up to, but not beyond, 60 min. For those participants presenting with staining, maximum severity and frequency were both observed at 60 min and were significantly greater (p < 0.05) than at 15, 30, and 45 min. CONCLUSION Solution induced corneal staining gradually increased after lens insertion to a maximum at 1h. This level was maintained until at least 2h post-insertion.

Efficacy of osmoprotectants on prevention and treatment of murine dry eye.

PURPOSE To evaluate the efficacy of osmoprotectants on prevention and treatment of dry eye in a murine model. METHODS Dry eye was induced in mice by using an intelligently controlled environmental system (ICES). Osmoprotectants betaine, L-carnitine, erythritol, or vehicle (PBS) were topically administered to eyes four times daily following two schedules: schedule 1 (modeling prevention): dosing started at the beginning of housing in ICES and lasted for 21 or 35 days; schedule 2 (modeling treatment): dosing started after ICES-housed mice developed dry eye (day 21), continuing until day 35. Treatment efficacy was evaluated for corneal fluorescein staining; corneal epithelial apoptosis by TUNEL and caspase-3 assays; goblet cell numbers by PAS staining; and expression of inflammatory mediators, TNF-α, IL-17, IL-6, or IL-1β by using RT-PCR on days 0, 14, 21, and/or 35. RESULTS Compared with vehicle, prophylactic administration of betaine, L-carnitine, or erythritol significantly decreased corneal staining and expression of TNF-α and IL-17 on day 21 (schedule 1). Treatment of mouse dry eye with osmoprotectants significantly reduced corneal staining on day 35 compared with day 21 (schedule 2). Relative to vehicle, L-carnitine treatment of mouse dry eye for 14 days (days 21 to 35) resulted in a significant reduction in corneal staining, number of TUNEL-positive cells, and expression of TNF-α, IL-17, IL-6, or IL-1β, as well as significantly increased the number of goblet cells. CONCLUSIONS Topical application of betaine, L-carnitine, or erythritol systematically limited progression of environmentally induced dry eye. L-carnitine can also reduce the severity of such dry-eye conditions.