Protection of 6-OHDA neurotoxicity by PGF2α through FP-ERK-Nrf2 signaling in SH-SY5Y cells

Acyclovir provides protection against 6-OHDA-induced neurotoxicity in SH-SY5Y cells through the kynurenine pathway

Parkinson's disease is one of the most prevalent neurodegenerative disorders worldwide. The kynurenine pathway associated with oxidative stress and neuroinflammation is recognized to contribute to its pathophysiology, although the exact mechanism is not fully elucidated. In neuroinflammation, IDO-1 catalyzes the conversion of tryptophan to neurotoxic QUIN through the kynurenine pathway. Consequently, QUIN increases oxidative stress via nNOS and NMDA, which causes neurodegeneration. Few studies have reported on the effect of different antiviral drugs in Parkinson's disease; the exact mechanism is still unknown. The antiviral acyclovir has been shown to have neuroprotective properties and can cross the blood-brain barrier. We examined acyclovir's effects and potential mechanisms in the 6-OHDA-induced in vitro model of Parkinson's disease in SH-SY5Y cells using biochemical, immunocytochemical, and in silico methods. MTT assay demonstrated that acyclovir significantly decreased cell mortality induced by the neurotoxic 6-OHDA at dosages of 3.2 µM, 6.4 µM, 12.8 µM, 25.6 µM, and 51.2 µM. In immunocytochemical analysis, acyclovir treatment decreased α-synuclein and TNF-α expressions in cells. In biochemical analyses, while IL-17A and TOS levels decreased depending on varying doses (1.6 µM, 3.2 µM, 6.4 µM, 12.8 µM), TAC levels increased. Using in silico analyses to investigate the mechanism showed that acyclovir docked with TNF-α, IL-17A, IDO-1, nNOS, α-synuclein, and NMDA. The findings demonstrated that acyclovir had neuroprotective effects by modulating the kynurenine pathway and decreasing neurodegeneration via QUIN inhibition in an in vitro Parkinson's disease model. Although the mechanisms of acyclovir's effects in Parkinson's disease are unclear, the results obtained from the experiments are encouraging.

Isorhamnetin ameliorates dopaminergic neuronal damage via targeting FOSL1 to activate AKT/mTOR in 6-OHDA-induced SH-SY5Y cells

Parkinson's disease (PD) is a chronic neurodegenerative disorder caused by loss of dopaminergic neurons in the substantia nigra compacta, which may result from mitochondrial dysfunction and oxidative stress. Isorhamnetin (Iso) has important antioxidative stress and antiapoptotic effects, this study investigated the effects of Iso on PD in vitro and its underlying mechanisms using a model of 6-hydroxydopamine (6-OHDA)-induced SH-SY5Y cell damage. The results showed that Iso significantly ameliorated 6-OHDA-induced SH-SY5Y cell injury, including decreased cell viability, increased apoptosis and senescence, and oxidative stress injury. Senescence-associated β-galactosidase (SA-β) staining, Western blot (WB), and immunofluorescence suggested that Iso significantly decreased the number of SA-β+ cells and the levels of senescence-associated proteins p21 and p16, and enhanced tyrosine hydroxylase level. Iso markedly reduced the number of apoptotic cells and the levels of cleaved caspase-3 and BAX, as detected by CCK-8, flow cytometry, and WB. The results of DCFH-DA, JC-1 staining, and the measurement of malondialdehyde (MDA) and superoxide dismutase (SOD) content indicated that Iso elevated reactive oxygen species (ROS) generation and mitochondrial membrane potential, lowered MDA content and raised SOD level in the 6-OHDA group. In-depth investigation revealed that Iso activated the AKT/mTOR signal via reducing the expression level of Fos-like antigen (FOSL1), which further exerted the protective effect in SH-SY5Y cells. Overexpression of FOSL1 attenuated the effect of Iso by inhibiting the AKT/mTOR signaling pathway. Taken together, Iso protects against senescence, apoptotic, and oxidative stress injury by targeting FOSL1 to activate the AKT/mTOR signaling pathway in 6-OHDA-induced SH-SY5Y cells, which may provide new insights for PD treatment.NEW & NOTEWORTHY Isorhamnetin (Iso) ameliorated neuronal activity damage, senescence, apoptosis, and oxidative stress injury in 6-hydroxydopamine (6-OHDA)-induced SH-SY5Y cells. Iso activated AKT/mTOR signaling pathway via inhibiting Fos-like antigen (FOSL1) in 6-OHDA-induced SH-SY5Y cells. Overexpression of FOSL1 attenuated the protective effect of Iso against 6-OHDA-induced neuronal damage in SH-SY5Y cells.

Tafluprost promotes axon regeneration after optic nerve crush via Zn2+-mTOR pathway

PURPOSE

To investigate whether Tafluprost could promote optic nerve regeneration in mice after optic nerve crush (ONC) and determine the underlying molecular mechanism.

METHODS

Tafluprost was injected into the vitreous body immediately after ONC. The level of Zn2+ in the inner plexiform layer (IPL) of the retina was stained using autometallography (AMG). The number of survival retinal ganglion cells (RGCs) was determined via dual staining with RGC markers Tuj1 and RBPMS. Individual axons that regenerated to 0.25, 0.5, 0.75 and 1 mm were manually counted in the whole-mount optic nerve labeled by cholera toxin B fragment (CTB). Immunofluorescence and Western blot were performed to detect protein expression levels. Pattern electroretinogram was used to evaluate RGCs function.

RESULTS

Tafluprost promoted RGC survival in a dose-dependent manner with an optimal concentration of 1 μM. Tafluprost significantly decreased ZnT-3 expression and Zn2+ accumulation in the IPL of retina. Tafluprost stimulated intense axonal regeneration and maintained RGCs function compared to control. Mechanistically, Tafluprost and Zn2+ elimination treatment (TPEN or ZnT-3 deletion) can activate the mTOR pathway with an improved percentage of pS6+ RGCs in the retina. However, rapamycin, a specific inhibitor of the mTOR1, inhibited the activation of the mTOR pathway and abolished the regenerative effect mediated by Tafluprost. Tafluprost also inhibited the upregulation of p62, LC3 and Beclin-1, attenuated the overactivation of microglia/macrophages and downregulated the expression of TNFα and IL-1β.

CONCLUSIONS

Our results suggest that Tafluprost promoted axon regeneration via regulation of the Zn2+-mTOR pathway, and provide novel research directions for glaucomatous optic nerve injury mechanisms.

Neuroaxonal and cellular damage/protection by prostanoid receptor ligands, fatty acid derivatives and associated enzyme inhibitors

Cellular and mitochondrial membrane phospholipids provide the substrate for synthesis and release of prostaglandins in response to certain chemical, mechanical, noxious and other stimuli. Prostaglandin D₂, prostaglandin E₂, prostaglandin F_2α, prostaglandin I₂ and thromboxane-A₂ interact with five major receptors (and their sub-types) to elicit specific downstream cellular and tissue actions. In general, prostaglandins have been associated with pain, inflammation, and edema when they are present at high local concentrations and involved on a chronic basis. However, in acute settings, certain endogenous and exogenous prostaglandins have beneficial effects ranging from mediating muscle contraction/relaxation, providing cellular protection, regulating sleep, and enhancing blood flow, to lowering intraocular pressure to prevent the development of glaucoma, a blinding disease. Several classes of prostaglandins are implicated (or are considered beneficial) in certain central nervous system dysfunctions (e.g., Alzheimer’s, Parkinson’s, and Huntington’s diseases; amyotrophic lateral sclerosis and multiple sclerosis; stroke, traumatic brain injuries and pain) and in ocular disorders (e.g., ocular hypertension and glaucoma; allergy and inflammation; edematous retinal disorders). This review endeavors to address the physiological/pathological roles of prostaglandins in the central nervous system and ocular function in health and disease, and provides insights towards the therapeutic utility of some prostaglandin agonists and antagonists, polyunsaturated fatty acids, and cyclooxygenase inhibitors.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson's disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

NRF2 Activation and Downstream Effects: Focus on Parkinson's Disease and Brain Angiotensin

Reactive oxygen species (ROS) are signalling molecules used to regulate cellular metabolism and homeostasis. However, excessive ROS production causes oxidative stress, one of the main mechanisms associated with the origin and progression of neurodegenerative disorders such as Parkinson's disease. NRF2 (Nuclear Factor-Erythroid 2 Like 2) is a transcription factor that orchestrates the cellular response to oxidative stress. The regulation of NRF2 signalling has been shown to be a promising strategy to modulate the progression of the neurodegeneration associated to Parkinson's disease. The NRF2 pathway has been shown to be affected in patients with this disease, and activation of NRF2 has neuroprotective effects in preclinical models, demonstrating the therapeutic potential of this pathway. In this review, we highlight recent advances regarding the regulation of NRF2, including the effect of Angiotensin II as an endogenous signalling molecule able to regulate ROS production and oxidative stress in dopaminergic neurons. The genes regulated and the downstream effects of activation, with special focus on Kruppel Like Factor 9 (KLF9) transcription factor, provide clues about the mechanisms involved in the neurodegenerative process as well as future therapeutic approaches.

Investigating the Regulation of Neural Differentiation and Injury in PC12 Cells Using Microstructure Topographic Cues

In this study, we designed and manufactured a series of different microstructure topographical cues for inducing neuronal differentiation of cells in vitro, with different topography, sizes, and structural complexities. We cultured PC12 cells in these microstructure cues and then induced neural differentiation using nerve growth factor (NGF). The pheochromocytoma cell line PC12 is a validated neuronal cell model that is widely used to study neuronal differentiation. Relevant markers of neural differentiation and cytoskeletal F-actin were characterized. Cellular immunofluorescence detection and axon length analysis showed that the differentiation of PC12 cells was significantly different under different isotropic and anisotropic topographic cues. The expression differences of the growth cone marker growth-associated protein 43 (GAP-43) and sympathetic nerve marker tyrosine hydroxylase (TH) genes were also studied in different topographic cues. Our results revealed that the physical environment has an important influence on the differentiation of neuronal cells, and 3D constraints could be used to guide axon extension. In addition, the neurotoxin 6-hydroxydopamine (6-OHDA) was used to detect the differentiation and injury of PC12 cells under different topographic cues. Finally, we discussed the feasibility of combining the topographic cues and the microfluidic chip for neural differentiation research.