Analytical and physicochemical characterisation of the senile cataract drug dipeptide β-alanyl-L-histidine (carnosine)

Recent progress and research trend of anti-cataract pharmacology therapy: A bibliometric analysis and literature review

Cataract is the leading cause of blindness worldwide. Cataract phacoemulsification combined with intraocular lens implantation causes great burden to global healthcare, especially for low- and middle-income countries. Such burden would be significantly relieved if cataracts can effectively be treated or delayed by non-surgical means. Excitingly, novel drugs have been developed to treat cataracts in recent decades. For example, oxysterols are found to be able to innovatively reverse lens clouding, novel nanotechnology-loaded drugs improve anti-cataract pharmacological effect, and traditional Chinese medicine demonstrates promising therapeutic effects against cataracts. In the present review, we performed bibliometric analysis to provide an overview perspective regarding the research status, hot topics, and academic trends in the field of anti-cataract pharmacology therapy. We further reviewed the curative effects and molecular mechanisms of anti-cataract drugs such as lanosterol, metformin, resveratrol and curcumin, and prospected the possibility of their clinical application in future.

Effects of Recombinant Human Epidermal Growth Factor Eye Drops Combined with Phacoemulsification on Short- and Long-Term Visual Acuity Recovery and Related Dry Eye Complications in Patients with Senile Cataract

Objective

To investigate the effects of recombinant human epidermal growth factor eye drops combined with phacoemulsification on short- and long-term visual acuity recovery and related dry eye complications in patients with senile cataract.

Methods

Sixty patients with senile cataract cured from January 2019 to January 2021 were enrolled in our hospital. The patients in the control group were arbitrarily assigned into the control and the research group. The former group received phacoemulsification, and the latter group received recombinant human epidermal growth factor (RhEGF) eye drops combined with phacoemulsification. The curative effect, the incidence of xerophthalmia, short-term and long-term vision improvement, changes of corneal endothelial cells, serum factors, and life quality scores were compared.

Results

The effective rate of the research group was 90.00%, and the effective rate of the control group was 66.67%; the curative effect of the research group was higher than that of the control group (P < 0.05). The incidence of dry eye in the research group was lower than that in the control group (P < 0.05). The short-term and long-term visual acuity improvement effect of the research group was better than that of the control group (P < 0.05). After treatment, the density of corneal endothelial cells in the research group was higher than that in the control group, while the proportion of hexagonal cells and the coefficient of variation of corneal endothelial cells in the research group were lower than those in the control group (P < 0.05). After treatment, IL-6 and TNF-α in the research group were lower than those in the control group (P < 0.05). Compared with the control group, the physical function, psychological function, social function, and healthy self-cognition scores of the research group were all lower (P < 0.05).

Conclusion

Cataract is the leading cause of blindness in the world. With the continuous improvement of cataract phacoemulsification technology, the incidence of some serious complications has gradually lessened. Xerophthalmia is one of the most obvious and predictable complications after cataract surgery and may affect the recovery of postoperative visual acuity. Recombinant human epidermal growth factor eye drops can effectively enhance the visual acuity of patients, promote the curative effect, and strengthen the life quality.

Hybrid thermosensitive-mucoadhesive in situ forming gels for enhanced corneal wound healing effect of L-carnosine

Purpose

Thermosensitive in situ gels have been around for decades but only a few have been translated into ophthalmic pharmaceuticals. The aim of this study was to combine the thermo-gelling polymer poloxamer 407 and mucoadhesive polymers chitosan (CS) and methyl cellulose (MC) for developing effective and long-acting ophthalmic delivery systems for L-carnosine (a natural dipeptide drug) for corneal wound healing.

Methods

The effect of different polymer combinations on parameters like gelation time and temperature, rheological properties, texture, spreading coefficients, mucoadhesion, conjunctival irritation potential, in vitro release, and ex vivo permeation were studied. Healing of corneal epithelium ulcers was investigated in a rabbit’s eye model.

Results

Both gelation time and temperature were significantly dependent on the concentrations of poloxamer 407 and additive polymers (chitosan and methyl cellulose), where it ranged from <10 s to several minutes. Mechanical properties investigated through texture analysis (hardness, adhesiveness, and cohesiveness) were dependent on composition. Promising spreading-ability, mucoadhesion, transcorneal permeation of L-carnosine, high ocular tolerability, and enhanced corneal epithelium wound healing were recorded for poloxamer 407/chitosan systems.

Conclusion

In situ gelling systems comprising combinations of poloxamer-chitosan exhibited superior gelation time and temperature, mucoadhesion, and rheological characteristics suitable for effective long-acting drug delivery systems for corneal wounds.

A Novel Quantum Dot-Based pH Probe for Long-Term Fluorescence Lifetime Imaging Microscopy Experiments in Living Cells

The use of two nanoparticles for quantitative pH measurements in live cells by means of fluorescence lifetime imaging microscopy (FLIM) is investigated here. These nanoparticles are based on CdSe/ZnS quantum dots (QDs), functionalized with N-acetylcysteine (CdSe/ZnS-A) and with a small peptide containing D-penicillamine and histidine (CdSe/ZnS-PH). CdSe/ZnS-A has tendency to aggregate and nonlinear pH sensitivity in a complex medium containing salts and macromolecules. On the contrary, CdSe/ZnS-PH shows chemical stability, low toxicity, efficient uptake in C3H10T1/2 cells, and good performance as an FLIM probe. CdSe/ZnS-PH also has key advantages over a recently reported probe based on a CdSe/ZnS QD functionalized with D-penicillamine (longer lifetimes and higher pH-sensitivity). A pH(±2σ) of 6.97 ± 0.14 was determined for C3H10T1/2 cells by FLIM employing this nanoprobe. In addition, the fluorescence lifetime signal remains nearly constant for C3H10T1/2 cells treated with CdSe/ZnS-PH for 24 h. These results show the promising applications of this nanoprobe to monitor the intracellular pH and cell state employing the FLIM technique.

Pegylated liquisomes: A novel combined passive targeting nanoplatform of L-carnosine for breast cancer

PEGylated Liquisomes (P-Liquisomes), a novel drug delivery system was designed for the first time by incorporating phospholipid complex in PEGylated liquid crystalline nanoparticles (P-LCNPs). L-carnosine (CN), a challenging dipeptide, has proven to be a promising anti-cancer drug. However, it exhibits high water solubility and extensive in-vivo degradation that halts its use. The objective of this work was to investigate the ability of our novel system to improve the CN anticancer activity by prolonging it's release and protecting it in-vivo. In-vitro appraisal revealed spherical light-colored vesicles encapsulated in the liquid crystals, confirming the successful formation of the combined system. P-Liquisomes were nano-sized (149.3 ± 1.4 nm), with high ZP (-40.2 ± 1.5 mV), complexation efficiency (97.5 ± 0.9%) and outstanding sustained release of only 75.4% released after 24 h, compared to P-LCNPs and Phytosomes. The results obtained with P-Liquisomes are considered as a break through compared to P-LCNPs or Phytosomes alone, especially when dealing with the hydrophilic CN. In-vitro cytotoxicity evaluation, revealed superior cytotoxic effect of P-Liquisomes (IC₅₀ = 25.9) after 24 h incubation. Besides, P-Liquisomes proved to be non-toxic in-vivo and succeeded to show superior chemopreventive activity manifested by reduction of; % tumor growth (7.1%), VEGF levels (14.3 pg/g tissue), cyclin D1 levels 15.5 ng/g tissue and elevation in caspase-3 level (36.4 ng/g tissue), compared to Phytosomes and CN solution. Conclusively, P-Liquisomes succeded to achieve the maximum therapeutic outcome of CN without altering its activity and might be used as a sustained delivery system for other promising hydrophilic compounds.

Chemotherapeutic potential of L-carnosine from stimuli-responsive magnetic nanoparticles against breast cancer model

Aim: L-carnosine-coated magnetic nanoparticles (CCMNPs) were developed to enhance chemotherapeutic activity of carnosine-dipeptide. Materials & methods: Surface grafting of MNPs with carnosine was contended by differential scanning calorimetry, infrared spectroscopy and x-ray diffraction. Physicochemical characterization and in vitro cytotoxicity on MCF-7 cell line was carried out. In vivo chemotherapeutic activity and toxicity was assessed by an Ehrlich Ascites tumor model. Results: CCMNPs possessed monodispersed size (120 nm), ζ (-27.3 mV), magnetization (51.52 emu/g) and entrapment efficiency (88.3%) with sustained release rate. CCMNPs showed 2.3-folds lower IC50 values compared with carnosine solution after 48 h. Targeted CCMNPs were specifically accumulated in tumor showing significant reduction in tumor size with no systemic toxicity. Significant reduction in VEGF and cyclin D1 levels were observed. Conclusion: The developed system endowed with responsiveness to an external stimulus can represent a promising magnetically targeted delivery system for carnosine site specific delivery.

Implications of Metal Binding and Asparagine Deamidation for Amyloid Formation

Increasing evidence suggests that amyloid formation, i.e., self-assembly of proteins and the resulting conformational changes, is linked with the pathogenesis of various neurodegenerative disorders such as Alzheimer’s disease, prion diseases, and Lewy body diseases. Among the factors that accelerate or inhibit oligomerization, we focus here on two non-genetic and common characteristics of many amyloidogenic proteins: metal binding and asparagine deamidation. Both reflect the aging process and occur in most amyloidogenic proteins. All of the amyloidogenic proteins, such as Alzheimer’s β-amyloid protein, prion protein, and α-synuclein, are metal-binding proteins and are involved in the regulation of metal homeostasis. It is widely accepted that these proteins are susceptible to non-enzymatic posttranslational modifications, and many asparagine residues of these proteins are deamidated. Moreover, these two factors can combine because asparagine residues can bind metals. We review the current understanding of these two common properties and their implications in the pathogenesis of these neurodegenerative diseases.

On the Relationship between Energy Metabolism, Proteostasis, Aging and Parkinson's Disease: Possible Causative Role of Methylglyoxal and Alleviative Potential of Carnosine

Recent research shows that energy metabolism can strongly influence proteostasis and thereby affect onset of aging and related disease such as Parkinson's disease (PD). Changes in glycolytic and proteolytic activities (influenced by diet and development) are suggested to synergistically create a self-reinforcing deleterious cycle via enhanced formation of triose phosphates (dihydroxyacetone-phosphate and glyceraldehyde-3-phosphate) and their decomposition product methylglyoxal (MG). It is proposed that triose phosphates and/or MG contribute to the development of PD and its attendant pathophysiological symptoms. MG can induce many of the macromolecular modifications (e.g. protein glycation) which characterise the aged-phenotype. MG can also react with dopamine to generate a salsolinol-like product, 1-acetyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinaline (ADTIQ), which accumulates in the Parkinson's disease (PD) brain and whose effects on mitochondria, analogous to MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), closely resemble changes associated with PD. MG can directly damage the intracellular proteolytic apparatus and modify proteins into non-degradable (cross-linked) forms. It is suggested that increased endogenous MG formation may result from either, or both, enhanced glycolytic activity and decreased proteolytic activity and contribute to the macromolecular changes associated with PD. Carnosine, a naturally-occurring dipeptide, may ameliorate MG-induced effects due, in part, to its carbonyl-scavenging activity. The possibility that ingestion of highly glycated proteins could also contribute to age-related brain dysfunction is briefly discussed.

On the Anticataractogenic Effects of L-Carnosine: Is It Best Described as an Antioxidant, Metal-Chelating Agent or Glycation Inhibitor?

Purpose. L-Carnosine is a naturally occurring dipeptide which recently gained popularity as an anticataractogenic agent due to its purported antioxidant activities. There is a paucity of research and conclusive evidence to support such claims. This work offers compelling data that help clarify the mechanism(s) behind the anticataract properties of L-carnosine. Methods. Direct in vitro antioxidant free radical scavenging properties were assayed using three different antioxidant (TEAC, CUPRAC, and DPPH) assays. Indirect in vitro and ex vivo antioxidant assays were studied by measuring glutathione bleaching capacity and total sulfhydryl (SH) capacity of bovine lens homogenates as well as hydrogen-peroxide-stress assay using human lens epithelial cells. Whole porcine lenses were incubated in high galactose media to study the anticataract effects of L-carnosine. MTT cytotoxicity assays were conducted on human lens epithelial cells. Results. The results showed that L-carnosine is a highly potent antiglycating agent but with weak metal chelating and antioxidant properties. There were no significant decreases in lens epithelial cell viability compared to negative controls. Whole porcine lenses incubated in high galactose media and treated with 20 mM L-carnosine showed a dramatic inhibition of advanced glycation end product formation as evidenced by NBT and boronate affinity chromatography assays. Conclusion. L-Carnosine offers prospects for investigating new methods of treatment for diabetic cataract and any diseases that are caused by glycation.

Phytosome-hyaluronic acid systems for ocular delivery of L-carnosine

This study reports on L-carnosine phytosomes as an alternative for the prodrug N-acetyl-L-carnosine as a novel delivery system to the lens. L-carnosine was loaded into lipid-based phytosomes and hyaluronic acid (HA)-dispersed phytosomes. L-carnosine-phospholipid complexes (PC) of different molar ratios, 1:1 and 1:2, were prepared by the solvent evaporation method. These complexes were characterized with thermal and spectral analyses. PC were dispersed in either phosphate buffered saline pH 7.4 or HA (0.1% w/v) in phosphate buffered saline to form phytosomes PC1:1, PC1:2, and PC1:2 HA, respectively. These phytosomal formulations were studied for size, zeta potential, morphology, contact angle, spreading coefficient, viscosity, ex vivo transcorneal permeation, and cytotoxicity using primary human corneal cells. L-carnosine-phospholipid formed a complex at a 1:2 molar ratio and phytosomes were in the size range of 380–450 nm, polydispersity index of 0.12–0.2. The viscosity of PC1:2 HA increased by 2.4 to 5-fold compared with HA solution and PC 1:2, respectively; significantly lower surface tension, contact angle, and greater spreading ability for phytosomes were also recorded. Ex vivo transcorneal permeation parameters showed significantly controlled corneal permeation of L-carnosine with the novel carrier systems without any significant impact on primary human corneal cell viability. Ex vivo porcine lenses incubated in high sugar media without and with L-carnosine showed concentration-dependent marked inhibition of lens brunescence indicative of the potential for delaying changes that underlie cataractogenesis that may be linked to diabetic processes.