Peperomia pellucida (L.) Kunth suppresses glycation-induced inflammatory response in human retinal pigment epithelial cell line ARPE-19 via JAK-STAT3 signaling.

The formation of advanced glycation end product (AGE) is a risk factor for diabetic retinopathy. Since the current treatment for diabetic retinopathy is accompanied by side effects, preliminary findings have suggested Peperomia pellucida (L.) Kunth as a potential alternative therapeutic option for diabetic retinopathy. This study aimed to elucidate the anti-inflammatory mechanism of P. pellucida in the AGE-stimulated human retinal pigment epithelial cell line ARPE-19. Phytochemical analysis revealed phenylpronanoids, terpenes, and fatty acids in P. pellucida. Through in vitro cell viability assay, the P. pellucida methanolic extract (IC50 = 8.70 mg/mL) and ethyl acetate fraction (IC50 = 7.34 mg/mL) were considered as non toxic for ARPE-19. AGE induced an inflammatory response in ARPE-19 by upregulating the gene (2.4-5.8-fold) and protein (1.4-2.3-fold) expression of signal transducer and activator of transcription 3 (STAT3), interleukin-8 (IL-8), monocyte chemoattractant protein-1, matrix metalloproteinase 2, and vascular endothelial growth factor. At 1.5 mg/mL, P. pellucida methanolic extract suppressed IL-8 expression (p < 0.05), implying its anti-inflammatory action at the early inflammatory stage through the Janus kinase (JAK)-STAT3 pathway. The methanolic extract also restored the ARPE-19 viability under AGE-induced inflammatory stress. The downregulation of inflammatory biomarkers along the JAK-STAT3 pathway suggested P. pellucida as a promising anti-inflammatory source for diabetic retinopathy.

Potential of medicinal plants to ameliorate neovascularization activities in diabetes: A systematic review.

Hyperglycemia in diabetes mediates the release of angiogenic factors, oxidative stress, hypoxia, and inflammation, which in turn stimulate angiogenesis. Excessive angiogenesis can cause diabetic retinopathy, diabetic neuropathy, and diabetic nephropathy. All of these complications are debilitating, which may lead to an increased susceptibility to lower-limb amputations due to ulcerations and infections. In addition, microvascular alterations, segmental demyelination, and endoneurial microangiopathy may cause progressive deterioration ultimately leading to kidney failure and permanent blindness. Some medicinal plants have potent anti-angiogenic, antioxidant or anti-inflammatory properties that can ameliorate angiogenesis in diabetes. The purpose of this systematic review is to demonstrate the potential of medicinal plants in ameliorating the neovascularization activities in diabetes. Manuscripts were searched from PubMed, Science Direct, and Scopus databases, and Google Scholar was used for searching additional papers. From 1862 manuscripts searched, 1854 were excluded based on inclusion and exclusion criteria and 8 were included into this systematic review, whereas the required information was extracted and summarized. All identified medicinal plants decreased the high blood glucose levels in diabetes, except the aqueous extract of Lonicerae japonicae flos (FJL) and Vasant Kusumakar Ras. They also increased the reduced body weight in diabetes, except the aqueous extract of FL and total lignans from Fructus arctii. However, methanolic extract of Tinospora cordifolia and Vasant Kusumakar Ras were not tested for their ability to affect the body weight. Besides, all medicinal plants identified in this systematic review decreased the vascular endothelial growth factor (VEGF) protein expression and vasculature activity demonstrated by histopathological examination indicating promising anti-angiogenic properties. All medicinal plants identified in this systematic review have a potential to ameliorate neovascularization activities in diabetes by targeting the mechanistic pathways related to oxidative stress, inflammation, and angiogenesis.

Comparative Analysis of In Vitro Enzyme Inhibitory Activities and Phytochemicals from Platycladus orientalis (L.) Franco via Solvent Partitioning Method.

The extraction of plant bioactive compounds from Platycladus orientalis (L.) Franco remains a great challenge due to the different chemical groups. This study aimed to compare the bioactive compounds with enzyme inhibitory effect from P. orientalis via solvent partitioning method. Dried leaf samples were macerated and fractionated with six solvents of different polarities. The phenolic, flavonoid, tannin, saponin, alkaloid and pharmacological activities including anti-inflammatory, anti-diabetic, antioxidant and anti-glycation potential were compared across the six plant fractions. Toxicity assessment was performed with an in vivo brine shrimp model. The varying levels of bioactive compounds in ethyl acetate (phenolics, flavonoids), hexane (saponins, tannins) and chloroform (alkaloids) fractions clearly demonstrated the significant impact of solvent polarity on the extraction of bioactive compounds. The reducing potential (r = 0.67), IC50 of α-amylase inhibition (r = -0.71), IC50 of advanced glycation end-product inhibition (r = -0.93) and dicarbonyl compound inhibition (r = 0.57) in the plant fractions were correlated (p<0.05) with the flavonoids. Besides, the alkaloid, saponin and tannin were associated with cyclooxygenase-1 inhibitory activity. Principal component analysis confirmed that solvent polarity (23.9%) and plant extraction yield (37.1%) collectively contributed to 61% of bioactivity variation in P. orientalis. Among the six plant fractions, ethyl acetate fraction exhibited relatively high anti-inflammatory, anti-diabetic, antioxidant and anti-glycation potential while the non-toxic methanolic and aqueous fractions displayed optimal hyaluronidase and lipoxygenase inhibitory activities, respectively. The current study has identified semi-polar ethyl acetate fraction of P. orientalis as a good alternative source of bioactive compounds for future pharmaceutical product development.

Peperomia pellucida (L.) Kunth and eye diseases: A review on phytochemistry, pharmacology and toxicology.

Peperomia pellucida (L.) Kunth is a medicinal plant used to manage inflammatory illnesses such as conjunctivitis, and gastrointestinal and respiratory tract disorders in tropical and subtropical regions. However, little is known about its pharmacological mechanism of action against eye diseases. This review aims to critically discuss the phytochemistry, pharmacology and toxicology of P. pellucida as well as its roles in the treatment of cataract, glaucoma and diabetic retinopathy. Recent developments in the uses of P. pellucida for healthcare and nutraceutical products by the pharmaceutical industry are also covered in this review. For this review, a literature search was performed with PubMed, ScienceDirect, SciFinder Scholar and Scopus databases, using relevant keywords. Among the various phytochemicals identified from P. pellucida, ß-caryophyllene, carotol, dillapiole, ellagic acid, pellucidin A, phytol and vitexin exhibit strong pharmacological activities within the mitogen-activated protein kinase and nuclear factor-κB signalling pathways in inflammatory eye diseases. The antihypertensive, anti-inflammatory, antioxidant, antihyperglycemic and anti-angiogenic activities displayed by P. pellucida extracts in many in vitro, in vivo and clinical studies suggest its potential role in the management of inflammatory eye diseases. P. pellucida extract was non-toxic against normal cell lines but displayed mild toxicity in animal models. The growing public interest in P. pellucida has inspired the nutraceutical and pharmaceutical industries to process the plant into health products. Although the potential pharmacological mechanisms against eye diseases have been summarized, further studies of the interactions among constituent phytochemicals from P. pellucida within various signalling pathways shall support the use of the plant as an alternative therapeutic source.

Comparative analyses on radical scavenging and cytotoxic activity of phenolic and flavonoid content from selected medicinal plants.

This study aimed to compare the total phenolic (TPC), flavonoid (TFC), radical scavenging and cytotoxic activities in the aqueous methanolic extracts of Angelica sinensis, Dioscorea polystachya, Ginkgo biloba, Glycyrrhiza uralensis and Lycium barbarum with two dietary plants: Brassica oleracea and Zingiber officinale. The TPC and TFC in medicinal plant extracts were 12-93% lower than Z. officinale as follows: L. barbarum > G. uralensis > A. sinensis > G. biloba > D. polystachya. The decreasing radical scavenging activity in medicinal plant extracts shared similar trend: G. uralensis > L. barbarum > A. sinensis > G. biloba > D. polystachya. Both TPC and TFC were positively correlated with radical scavenging and cytotoxic activities. All medicinal plants were considered inactive (LC50 > 0.2 mg/ml) and safe for consumption. The TPC, TFC, radical scavenging and cytotoxic activities in the medicinal plants were plant-part dependant, in particular L. barbarum and G. uralensis.

Peperomia pellucida (L.) Kunth herbal tea: Effect of fermentation and drying methods on the consumer acceptance, antioxidant and anti-inflammatory activities.

This study aimed to compare the effect of fermentation and drying on the organoleptic characteristic, total phenolic content, antioxidant and anti-inflammatory activities of Peperomia pellucida (L.) Kunth tea with commercial Camellia sinensis tea. The phenolic content, antioxidant and anti-inflammatory activities in P. pellucida were significantly (p < 0.05) lower than C. sinensis, irrespective of the fermentation and drying methods. Although fermentation decreased the total phenolics, flavonoids and antioxidant activity in both P. pellucida and C. sinensis teas, the anti-inflammatory potential of P. pellucida was significantly (p < 0.05) improved. Principle component analysis revealed that fermentation and drying methods contributed to respective 42.3% and 27.2% of activity variation in P. pellucida. The browning index was positively correlated with fermentation index (r = 0.670, p < 0.05) of leaves samples. Overall, unfermented and fermented P. pellucida leaves were best dried with microwaving and freeze drying, respectively for optimal antioxidant and anti-inflammatory activities with favorable consumer's acceptance.

Hyperglycemia and Diabetes Downregulate the Functional Expression of TRPV4 Channels in Retinal Microvascular Endothelium.

Retinal endothelial cell dysfunction is believed to play a key role in the etiology and pathogenesis of diabetic retinopathy. Numerous studies have shown that TRPV4 channels are critically involved in maintaining normal endothelial cell function. In the current paper, we demonstrate that TRPV4 is functionally expressed in the endothelium of the retinal microcirculation and that both channel expression and activity is downregulated by hyperglycaemia. Quantitative PCR and immunostaining demonstrated molecular expression of TRPV4 in cultured bovine retinal microvascular endothelial cells (RMECs). Functional TRPV4 activity was assessed in cultured RMECs from endothelial Ca2+-responses recorded using fura-2 microfluorimetry and electrophysiological recordings of membrane currents. The TRPV4 agonist 4α-phorbol 12,13-didecanoate (4-αPDD) increased [Ca2+]i in RMECs and this response was largely abolished using siRNA targeted against TRPV4. These Ca2+-signals were completely inhibited by removal of extracellular Ca2+, confirming their dependence on influx of extracellular Ca2+. The 4-αPDD Ca2+-response recorded in the presence of cyclopiazonic acid (CPA), which depletes the intracellular stores preventing any signal amplification through store release, was used as a measure of Ca2+-influx across the cell membrane. This response was blocked by HC067047, a TRPV4 antagonist. Under voltage clamp conditions, the TRPV4 agonist GSK1016790A stimulated a membrane current, which was again inhibited by HC067047. Following incubation with 25 mM D-glucose TRPV4 expression was reduced in comparison with RMECs cultured under control conditions, as were 4αPDD-induced Ca2+-responses in the presence of CPA and ion currents evoked by GSK1016790A. Molecular expression of TRPV4 in the retinal vascular endothelium of 3 months' streptozotocin-induced diabetic rats was also reduced in comparison with that in age-matched controls. We conclude that hyperglycaemia and diabetes reduce the molecular and functional expression of TRPV4 channels in retinal microvascular endothelial cells. These changes may contribute to diabetes induced endothelial dysfunction and retinopathy.

Evidence supporting a role for N-(3-formyl-3,4-dehydropiperidino)lysine accumulation in Müller glia dysfunction and death in diabetic retinopathy.

PURPOSE: Recent evidence suggests that neuroglial dysfunction and degeneration contributes to the etiology and progression of diabetic retinopathy. Advanced lipoxidation end products (ALEs) have been implicated in the pathology of various diseases, including diabetes and several neurodegenerative disorders. The purpose of the present study was to investigate the possible link between the accumulation of ALEs and neuroretinal changes in diabetic retinopathy. METHODS: Retinal sections obtained from diabetic rats and age-matched controls were processed for immunohistochemistry using antibodies against several well defined ALEs. In vitro experiments were also performed using a human Müller (Moorfields/Institute of Ophthalmology-Müller 1 [MIO-M1]) glia cell line. Western blot analysis was used to measure the accumulation of the acrolein-derived ALE adduct Nε-(3-formyl-3,4-dehydropiperidino)lysine (FDP-lysine) in Müller cells preincubated with FDP-lysine-modified human serum albumin (FDP-lysine-HSA). Responses of Müller cells to FDP-lysine accumulation were investigated by analyzing changes in the protein expression of heme oxygenase-1 (HO-1), glial fibrillary acidic protein (GFAP), and the inwardly rectifying potassium channel Kir4.1. In addition, mRNA expression levels of vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), and tumor necrosis factor-α (TNFα) were determined by reverse transcriptase PCR (RT-PCR). Apoptotic cell death was evaluated by fluorescence-activated cell sorting (FACS) analysis after staining with fluorescein isothiocyanate (FITC)-labeled annexin V and propidium iodide. RESULTS: No significant differences in the levels of malondialdehyde-, 4-hydroxy-2-nonenal-, and 4-hydroxyhexenal-derived ALEs were evident between control and diabetic retinas after 4 months of diabetes. By contrast, FDP-lysine immunoreactivity was markedly increased in the Müller glia of diabetic rats. Time-course studies revealed that FDP-lysine initially accumulated within Müller glial end feet after only a few months of diabetes and thereafter spread distally throughout their inner radial processes. Exposure of human Müller glia to FDP-lysine-HSA led to a concentration-dependent accumulation of FDP-lysine-modified proteins across a broad molecular mass range. FDP-lysine accumulation was associated with the induction of HO-1, no change in GFAP, a decrease in protein levels of the potassium channel subunit Kir4.1, and upregulation of transcripts for VEGF, IL-6, and TNF-α. Incubation of Müller glia with FDP-lysine-HSA also caused apoptosis at high concentrations. CONCLUSIONS: Collectively, these data strongly suggest that FDP-lysine accumulation could be a major factor contributing to the Müller glial abnormalities occurring in the early stages of diabetic retinopathy.

Patients with congenital hypothyroidism demonstrate different altered expression of plasma fibrinogen and haptoglobin polypeptide chains.

OBJECTIVES: To compare the plasma protein profiles of treated and untreated congenital hypothyroidism (CH) patients with those of normal control infants. DESIGN AND METHODS: Plasma samples were subjected to two-dimensional gel electrophoresis and silver staining or lectin detection. Resolved protein spots were analyzed by using computerized densitometry software. RESULTS: The significant enhanced expression of the fibrinogen gamma-chain and reduced expression of haptoglobin beta-chain were demonstrated in the profiles of untreated CH patients using both silver staining and lectin detection methods. Lectin detection resolved only a single cluster of the haptoglobin beta-chain for the untreated patients, in contrast to five isoform clusters detected in the controls' and treated CH patients' profiles. CONCLUSIONS: Plasma from untreated CH patients demonstrated different altered expression of fibrinogen and haptoglobin polypeptide chains, which was normalized when patients were treated. Our data also suggest differences in structures of the N-glycans of haptoglobin beta-chain of the untreated CH patients.