Curcumin Inhibits Neuronal Loss in the Retina and Elevates Ca²⁺/Calmodulin-Dependent Protein Kinase II Activity in Diabetic Rats

Is CaMKII friend or foe for cell apoptosis in eye?: A narrative review

Ca2+/calmodulin-dependent protein kinase II (CaMKII) controls cell proliferation, differentiation, apoptosis, and other biological processes that have an essential role in eye diseases. However, it seems that previous studies have generated conflicting conclusions about the effect of CaMKII on cell apoptosis. In this review, we explore the positive and potentially deleterious effects of CaMKII on eye cell apoptosis. We can safely conclude that the early elevation of CaMKII could be viewed as a promoter of cell apoptosis. Overexpression of CaMKII by transfection or pretreatment with drugs helped combat cell apoptosis.

The functions of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in diabetes progression

The increase in blood glucose causes a myriad of pathways and molecular components to malfunction, leading to diabetes. Diabetes affects each organ differently by activating distinct pathways. It has an impact on the liver, pancreas, kidney (nephropathy), eyes (retinopathy), and nervous system (neuropathy). Understanding the effects of diabetes on each organ is the first step in developing a sustained treatment for the disease. Among the many cellular molecules impacted by diabetes is Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), a complex Ca²⁺/calmodulin-activated serine/threonine-protein kinase. When intracellular [Ca²⁺] rises, it binds to calmodulin (CaM) to produce Ca²⁺/CaM, which activates CaMKIIs. This factor is involved in the pancreas, liver, heart, muscles, and various organs. Thus, Understanding CaMKII action in each organ is critical for gaining a complete picture of diabetic complications. Therefore, this review covers CaMKII's functions in many organs and how it affects and has been affected by diabetes.

Protection of leukemia inhibitory factor against high-glucose-induced human retinal endothelial cell dysfunction

PURPOSE

In the study, we aimed to explore the mechanism of leukaemia inhibitory factor (LIF) affects hyperglycaemic induced retinopathy by regulating CaMKII-CREB pathway.

METHODS

Human retinal endothelial cell (HRECs) induced by high glucose to simulate one of the pathogenesis in the diabetic retinopathy (DR) model. After LIF treatment, cell viability was detected by CCK-8 and apoptosis was detected by flow cytometry. Angiogenesis was detected by in vitro tube formation. The expression levels of inflammatory, angiogenesis related proteins and CaMKII-CREB were detected by western blot. The gene level of angiogenesis was detected by qRT-PCR. HE staining was used to detect pathological changes of retinopathy in diabetic mice after LIF treatment.

RESULTS

Our results showed that LIF significantly increased hyperglycaemic-induced cell viability and inhibited apoptosis. Western blot results showed that LIF could down-regulate the expression levels of inflammatory cytokines such as IL-1β, IL-6 and TNF-α. In addition, angiogenesis of HRECs was inhibited by LIF in tubulisation experiments. LIF can down-regulate protein and gene levels of VEGF and HIF-1α via western blot and qRT-PCR. In diabetic mice induced by STZ, LIF could down-regulate the protein level of VEGF, HIF-1α, p-CaMKII and p-CREB, which suggest that LIF could inhibit retinal angiogenesis in diabetic mice. The results of HE staining showed that LIF could alleviate the damage of retinopathy in diabetic mice.

CONCLUSION

LIF could alleviate the damage of diabetic retinopathy by modulating the CaMKII/CREB signalling pathway to inhibit inflammatory response and angiogenesis.

Inherited Retinal Dystrophies: Role of Oxidative Stress and Inflammation in Their Physiopathology and Therapeutic Implications

Inherited retinal dystrophies (IRDs) are a large group of genetically and clinically heterogeneous diseases characterized by the progressive degeneration of the retina, ultimately leading to loss of visual function. Oxidative stress and inflammation play fundamental roles in the physiopathology of these diseases. Photoreceptor cell death induces an inflammatory state in the retina. The activation of several molecular pathways triggers different cellular responses to injury, including the activation of microglia to eliminate debris and recruit inflammatory cells from circulation. Therapeutical options for IRDs are currently limited, although a small number of patients have been successfully treated by gene therapy. Many other therapeutic strategies are being pursued to mitigate the deleterious effects of IRDs associated with oxidative metabolism and/or inflammation, including inhibiting reactive oxygen species’ accumulation and inflammatory responses, and blocking autophagy. Several compounds are being tested in clinical trials, generating great expectations for their implementation. The present review discusses the main death mechanisms that occur in IRDs and the latest therapies that are under investigation.

Neuronal Epac1 mediates retinal neurodegeneration in mouse models of ocular hypertension

Progressive loss of retinal ganglion cells (RGCs) leads to irreversible visual deficits in glaucoma. Here, we found that the level of cyclic AMP and the activity and expression of its mediator Epac1 were increased in retinas of two mouse models of ocular hypertension. Genetic depletion of Epac1 significantly attenuated ocular hypertension–induced detrimental effects in the retina, including vascular inflammation, neuronal apoptosis and necroptosis, thinning of ganglion cell complex layer, RGC loss, and retinal neuronal dysfunction. With bone marrow transplantation and various Epac1 conditional knockout mice, we further demonstrated that Epac1 in retinal neuronal cells (especially RGCs) was responsible for their death. Consistently, pharmacologic inhibition of Epac activity prevented RGC loss. Moreover, in vitro study on primary RGCs showed that Epac1 activation was sufficient to induce RGC death, which was mechanistically mediated by CaMKII activation. Taken together, these findings indicate that neuronal Epac1 plays a critical role in retinal neurodegeneration and suggest that Epac1 could be considered a target for neuroprotection in glaucoma.

A novel hippocampus metabolite signature in diabetes mellitus rat model of diabetic encephalopathy

Diabetic encephalopathy (DE) is one of the chronic complications of diabetes. Even then, the molecular mechanism underlying DE remains unexplored. In this study, we have made an attempt to investigate the metabolic changes associated with the streptozocin (STZ)-induced cognitive dysfunction in the hippocampus of the rat model, a classical rodent model for DE, with the help of Gas Chromatography-Mass Spectrometry-based method. The STZ injections led to the rise of mean blood glucose levels in the diabetes mellitus (DM) group of rats as compared to the control (CON) group of rats throughout the experiment. However, we did not find any significant difference between the blood glucose levels of the DM & the CON groups of rats before the STZ injection. The results indicated a behavioral and morphological cognitive dysfunction in the DM groups of rats. The metabolomic investigation of these DE rats demonstrated a lower level of N-acetylaspartate and dihydroxyacetone phosphate accompanied by a higher level of homocysteine and glutamate as against the CON group of rats. The outcome of this study may unravel the underlying pathophysiological mechanism of DE. Also, the metabolomic data from this study may provide a platform for the development of DE biomarkers.

Curcumin diminishes cisplatin-induced apoptosis and mitochondrial oxidative stress through inhibition of TRPM2 channel signaling pathway in mouse optic nerve

Background: Cisplatin (CiSP), a chemotherapeutic agent, is widely used to treat several types of cancers. However, its clinical use is limited due to adverse side effects caused by excessive production of reactive oxygen species (ROS) and death of neurons. The transient receptor potential (TRP) melastatin 2 (TRPM2) cation channel is activated by ADP-ribose (ADPR) and ROS. The protective effect of curcumin (CURCU) against CiSP-induced apoptosis and mitochondrial ROS through inhibition of TRP channels in several types of neuron except optic nerve, was recently reported. The aim of the current study is to clarify the protective effect of CURCU on CiSP-induced mitochondrial oxidative injury and TRPM2 activation in the mice optic nerve and SH-SY5Y human derived neuronal cells.Material and methods: The SH-SY5Y cells and mice were divided into four groups: Control, CURCU, CiSP, and CURCU + CiSP. The mice were treated for 14 days and the cells were incubated with CiSP and CURCU for 24 h.Results: CURCU and PARP-1 inhibitor (PJ34) treatments ameliorated CiSP-induced mitochondrial membrane depolarization, mitochondrial and cytosolic ROS levels and neuronal death in the optic nerve. In the patch-clamp of SH-SY5Y cells and laser confocal microscopy experiments of optic nerve, CURCU and TRPM2 blocker treatments also decreased ADPR-induced TRPM2 currents and cytosolic free calcium ion (Ca²⁺) concentration, suggesting a suppression of Ca²⁺ influx and neuronal death.Conclusion: CURCU prevents CiSP-induced optic nerve oxidative injury and cell death by suppressing mitochondrial ROS production via regulating TRPM2 signaling pathways. CURCU may serve as a potential therapeutic target against CiSP-induced toxicity in the optic nerve of CiSP-treated patients.

Bioactivity, Health Benefits, and Related Molecular Mechanisms of Curcumin: Current Progress, Challenges, and Perspectives

Curcumin is a principal curcuminoid of turmeric (Curcuma longa), which is commonly used as a spice in cooking and a yellow pigment in the food processing industry. Recent studies have demonstrated that curcumin has a variety of biological activities and pharmacological performances, providing protection and promotion of human health. In addition to presenting an overview of the gut metabolism of curcumin, this paper reviews the current research progress on its versatile bioactivity, such as antioxidant, anti-inflammatory, and immune-regulatory activities, and also intensively discusses its health benefits, including the protective or preventive effects on cancers and diabetes, as well as the liver, nervous system, and cardiovascular systems, highlighting the potential molecular mechanisms. Besides, the beneficial effects of curcumin on human are further stated based on clinical trials. Considering that there is still a debate on the beneficial effects of curcumin, we also discuss related challenges and prospects. Overall, curcumin is a promising ingredient of novel functional foods, with protective efficacy in preventing certain diseases. We hope this comprehensive and updated review will be helpful for promoting human-based studies to facilitate its use in human health and diseases in the future.

Bridging Type 2 Diabetes and Alzheimer's Disease: Assembling the Puzzle Pieces in the Quest for the Molecules With Therapeutic and Preventive Potential

Type 2 diabetes (T2D) and Alzheimer's disease (AD) are two age-related amyloid diseases that affect millions of people worldwide. Broadly supported by epidemiological data, the higher incidence of AD among type 2 diabetic patients led to the recognition of T2D as a tangible risk factor for the development of AD. Indeed, there is now growing evidence on brain structural and functional abnormalities arising from brain insulin resistance and deficiency, ultimately highlighting the need for new approaches capable of preventing the development of AD in type 2 diabetic patients. This review provides an update on overlapping pathophysiological mechanisms and pathways in T2D and AD, such as amyloidogenic events, oxidative stress, endothelial dysfunction, aberrant enzymatic activity, and even shared genetic background. These events will be presented as puzzle pieces put together, thus establishing potential therapeutic targets for drug discovery and development against T2D and diabetes-induced cognitive decline-a heavyweight contributor to the increasing incidence of dementia in developed countries. Hoping to pave the way in this direction, we will present some of the most promising and well-studied drug leads with potential against both pathologies, including their respective bioactivity reports, mechanisms of action, and structure-activity relationships.

Curcumin inhibits apoptosis by regulating intracellular calcium release, reactive oxygen species and mitochondrial depolarization levels in SH-SY5Y neuronal cells

Neurological diseases such as Alzheimer's and Parkinson's diseases are incurable progressive neurological disorders caused by the degeneration of neuronal cells and characterized by motor and non-motor symptoms. Curcumin, a turmeric product, is an anti-inflammatory agent and an effective reactive oxygen and nitrogen species scavenging molecule. Hydrogen peroxide (H2O2) is the main source of oxidative stress, which is claimed to be the major source of neurological disorders. Hence, in this study we aimed to investigate the effect of curcumin on Ca(2+) signaling, oxidative stress parameters, mitochondrial depolarization levels and caspase-3 and -9 activities that are induced by the H2O2 model of oxidative stress in SH-SY5Y neuronal cells. SH-SY5Y neuronal cells were divided into four groups namely, the control, curcumin, H2O2, and curcumin + H2O2 groups. The dose and duration of curcumin and H2O2 were determined from published data. The cells in the curcumin, H2O2, and curcumin + H2O2 groups were incubated for 24 h with 5 µM curcumin and 100 µM H2O2. Lipid peroxidation and cytosolic free Ca(2+) concentrations were higher in the H2O2 group than in the control group; however, their levels were lower in the curcumin and curcumin + H2O2 groups than in the H2O2 group alone. Reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) values were lower in the H2O2 group although they were higher in the curcumin and curcumin + H2O2 groups than in the H2O2 group. Caspase-3 activity was lower in the curcumin group than in the H2O2 group. In conclusion, curcumin strongly induced modulator effects on oxidative stress, intracellular Ca(2+) levels, and the caspase-3 and -9 values in an experimental oxidative stress model in SH-SY5Y cells.