Toxicity

This study aimed to investigate the role of quercetin in myopic ciliary muscle remodeling through the regulation of SIRT1 expression. To this end, a randomized controlled trial was conducted using negative lens-induced myopic (LIM) guinea pig models for durations of 4 weeks and 6 weeks, with subjects administered quercetin (QUE) or SRT1720. Changes in axial lengths and refractive errors were measured at 4 and 6 weeks. Subsequently, protein expression (e.g., SIRT1, KEAP1, NRF2, MMP-2, and TIMP-2) in ciliary muscles was analyzed by Western blotting, while the expression of inflammatory cytokines (e.g., TNF-α, IL-6, and IL-10) was quantified via ELISA, and ciliary muscle morphologies were assessed using hematoxylin and eosin (H&E) staining and optical coherence tomography (OCT). Calcium fluxes, reactive oxygen species (ROS) levels, and mitochondrial membrane potentials (ΔΨm) were measured via noninvasive microtests and flow cytometry. Compared with the LIM group, the QUE and SIRT1 activator (SRT1720) intervention groups presented significantly reduced axial elongation amounts and refractive errors (P < 0.01), along with thickened ciliary muscles and improved fiber alignments. Additionally, the calcium influx and ROS levels were significantly reduced, and the ΔΨm levels were partially restored. Furthermore, Western blotting revealed upregulated SIRT1, NRF2, and TIMP-2 expression but downregulated KEAP1 and MMP-2 expression in the intervention groups, and ELISA revealed decreased inflammatory responses. In conclusion,quercetin could play a protective role by increasing the expression of SIRT1, which in turn alleviated KEAP1/NRF2-induced oxidative stress and mitigated NF-κB-driven inflammatory damage, thereby ameliorating ciliary muscle remodeling and potentially delaying the progression of myopia.

Background: The ciliary muscle, a critical intraocular smooth muscle, plays a potent role in ocular accommodation. Investigating the potential detrimental effects on the ciliary muscle during prolonged contraction and precise mechanism underlying the cell damage hold significance in treating ciliary muscle dysfunction. The effect and mechanism of vitamin E (VitE), an antioxidant, in mitigating these adverse effects of prolonged contraction remains to be thoroughly elucidated. Methods: A guinea pig model of prolonged contraction of the ciliary muscle was established through topical administration of carbachol, and primary ciliary muscle cells isolated from guinea pigs were used for in vitro experiments. Results: The ophthalmic examination results demonstrated that prolonged contraction of the ciliary muscle impaired accommodative function in guinea pigs. This condition may lead to disrupted cellular migration, intracellular adenosine triphosphate depletion, decreased mitochondrial membrane potential, and reactive oxygen species accumulation. Further examination revealed that carbachol induced darker-stained mitochondrial membranes and diminished cristae density, consistent with morphological features of ferroptosis. Moreover, sustained cell contraction modulated specific contraction-related proteins (α-smooth muscle actin), concurrently decreased the expression of antioxidant proteins (glutathione peroxidase, superoxide dismutase, catalase, and GSH) in both tissue specimens and cells, culminating in ferroptosis in vivo and in vitro experiments. Our findings demonstrated that pretreatment with VitE alleviated oxidative injury and mitigated ferroptosis. Additionally, knocking down acetyl-coenzyme A thiosterase 7 attenuated the beneficial effect of VitE. Conclusions: These findings collectively indicated that VitE presented a viable approach to ameliorate oxidative stress and ferroptosis induced by prolonged contraction of the ciliary muscle via activating acetyl-coenzyme A thiosterase 7.

Background: Aging-induced decline in ciliary muscle function is an important factor in visual accommodative deficits in elderly adults. With this study, we provide an innovative investigation of the interaction between ciliary muscle aging and oxidative stress. Methods: Tricolor guinea pigs were used for the experiments in vivo and primary guinea pig ciliary smooth muscle cells were used for the experiments in vitro.Results: We enriched for genes associated with muscle-aging-lutein relationship using bioinformatics, including Nuclear factor-erythroid 2-related factor-2 (Nrf2), Glutathione Peroxidase (GPx) gene family, Superoxide Dismutase (SOD) gene family, NAD(P)H: Quinone Oxidoreductase 1 (NQO1) and Heme Oxygenase-1 (HO-1). After gavage to aged guinea pigs, lutein reduced Reactive Oxygen Species (ROS) and P21 levels in senescent ciliary muscle; lutein decreased refractive error and restored accommodation of the eye. In addition, lutein increased GPx, SOD, and Catalase (CAT) levels in serum; lutein increased GPx and CAT levels in ciliary bodies. Lutein regulated the expression of proteins such as Nrf2, Kelch-like ECH-associated protein 1 (Keap1), and downstream proteins in senescent ciliary bodies. Similarly, guinea pig ciliary muscle cell senescence was associated with oxidative stress. In vitro, 100 μM lutein reversed the damage caused by 800 μM H2O2; it reduced Senescence-Associated β-galactosidase (SA-β-Gal) and ROS activites, cell apoptosis and cell migration. Also, lutein increased the expression of smooth muscle contractile proteins. Lutein also increased the expression of Nrf2, GPx2, NQO1 and HO-1, decreased the expression of Keap1. A reduction in Nrf2 activity led to a reduction in the ability of lutein to activate antioxidant enzymes in the cells, thus reducing its inhibitory effect on cell senescence. Conclusion: lutein improved resistance to oxidative stress in senescent ciliary muscle in vivo and in vitro by regulating the Keap1/Nrf2/Antioxidant Response Element pathway. We have innovatively demonstrated the molecular pharmacological mechanism by which lutein reverse age-related ciliary muscle systolic and diastolic deficits.

The ciliary muscle constitutes a crucial element in refractive regulation. Investigating the pathophysiological mechanisms within the ciliary muscle during excessive contraction holds significance in treating ciliary muscle dysfunction. A guinea pig model of excessive contraction of the ciliary muscle induced by drops pilocarpine was employed, alongside the primary ciliary muscle cells was employed in in vitro experiments. The results of the ophthalmic examination showed that pilocarpine did not significantly change refraction and axial length during the experiment, but had adverse effects on the regulatory power of the ciliary muscle. The current data reveal notable alterations in the expression profiles of hypoxia inducible factor 1 (HIF-1α), ATP2A2, P53, α-SMA, Caspase-3, and BAX within the ciliary muscle of animals subjected to pilocarpine exposure, alongside corresponding changes observed in cultured cells treated with pilocarpine. Augmented levels of ROS were detected in both tissue specimens and cells, culminating in a significant increase in cell apoptosis in in vivo and in vitro experiments. Further examination revealed that pilocarpine induced an increase in intracellular Ca²⁺ levels and disrupted MMP, as evidenced by mitochondrial swelling and diminished cristae density compared to control conditions, concomitant with a noteworthy decline in antioxidant enzyme activity. However, subsequent blockade of Ca²⁺ channels in cells resulted in downregulation of HIF-1α, ATP2A2, P53, α-SMA, Caspase-3, and BAX expression, alongside ameliorated mitochondrial function and morphology. The inhibition of Ca²⁺ channels presents a viable approach to mitigate ciliary cells damage and sustain proper ciliary muscle function by curtailing the mitochondrial damage induced by excessive contractions.

Fluorescent proteins (FPs) have been widely used to investigate cellular and molecular interactions and trace biological events in many applications. Some of the FPs have been demonstrated to cause undesirable cellular damage by light-induced ROS production in vivo or in vitro. However, it remains unknown if one of the most popular FPs, tdTomato, has similar effects in neuronal cells. In this study, we discovered that tdTomato expression led to unexpected retinal dysfunction and ultrastructural defects in the transgenic mouse retina. The retinal dysfunction mainly manifested in the reduced photopic electroretinogram (ERG) responses and decreased contrast sensitivity in visual acuity, caused by mitochondrial damages characterized with cellular redistribution, morphological modifications and molecular profiling alterations. Taken together, our findings for the first time demonstrated the retinal dysfunction and ultrastructural defects in the retinas of tdTomato-transgenic mice, calling for a more careful design and interpretation of experiments involved in FPs.