Zinc accumulation aggravates cerebral ischemia/reperfusion injury by promoting inflammation

Neuroprotective Effect of Ganoderic Acid against Focal Ischemic Stroke Induced by Middle Cerebral Artery Occlusion in the Rats via Suppression of Oxidative Stress and Inflammation

Stroke is recognized as a leading cause of disability and mortality worldwide, posing a significant challenge, particularly in developing countries. The current study aimed to evaluate the neuroprotective effect of Ganoderic acid (GA) against focal ischemic stroke in rats.

MATERIAL AND METHODS

Swiss Wistar rats were used for the current study. The rats were subjected to middle cerebral artery occlusion (MCAO) to simulate transient focal ischemia, followed by reperfusion. Various neurological parameters, including infarct size, neurological deficit score, brain water content, Evans blue leakage, nitric oxide (NO), inducible nitric oxide synthase (iNOS), lactate dehydrogenase (LDH), antioxidant levels, inflammatory cytokines, apoptosis markers, inflammatory parameters, and matrix metalloproteinases (MMP) levels, were estimated. Additionally, mRNA expressions were evaluated in the brain tissue.

RESULTS

Dose dependently treatment of GA significantly (P < 0.001) suppressed the infarct size, neurological deflects score, brain water, evans blue leakage, NO, iNOS, LDH, C-X-C chemokine receptor type 4 (CXCR-4), monocyte chemoattractant protein-1 (MCP-1), S100 calcium-binding protein B (S-100β) and K+-Cl- cotransporter 1 (KCC1) positive cells. GA altered the level of oxidative stress parameters like Total antioxidant capacity (T-AOC), 8-hydroxy-2'-deoxyguanosine (8-OhdG), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH), malonaldehyde (MDA); cytokines viz., tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), IL-1β, IL-6, IL-9, IL-10; inflammatory parameters such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), prostaglandin (PGE2), Nuclear factor kappa B (NF-κB); apoptosis parameters like B-cell leukemia/lymphoma 2 protein (Bcl-2), Bcl-2-associated protein x (Bax), Caspase-3; matrix metallopeptidase (MMP) parameters like MMP-2, MMP-3, and MMP-9, respectively. GA remarkably suppressed the mRNA expression of TRL-4, Syndecan-1, CSF, Aquaporin-1, OCT3, and RFX1.

CONCLUSION

Ganoderic acid exhibited the protection against the cerebral ischemia reperfusion via multiple mechanism.

Zinc Toxicity: Understanding the Limits

Zinc, a vital trace element, holds significant importance in numerous physiological processes within the body. It participates in over 300 enzymatic reactions, metabolic functions, regulation of gene expression, apoptosis and immune modulation, thereby demonstrating its essential role in maintaining overall health and well-being. While zinc deficiency is associated with significant health risks, an excess of this trace element can also lead to harmful effects. According to the World Health Organization (WHO), 6.7 to 15 mg per day are referred to be the dietary reference value. An excess of the recommended daily intake may result in symptoms such as anemia, neutropenia and zinc-induced copper deficiency. The European Food Safety Authority (EFSA) defines the tolerable upper intake level (UL) as 25 mg per day, whereas the Food and Drug Administration (FDA) allows 40 mg per day. This review will summarize the current knowledge regarding the calculation of UL and other health risks associated with zinc. For example, zinc intake is not limited to oral consumption; other routes, such as inhalation or topical application, may also pose risks of zinc intoxication.

Protective effect of zinc gluconate on intestinal mucosal barrier injury in antibiotics and LPS-induced mice

Objective

The aim of the study is to investigate the function and mechanism of Zinc Gluconate (ZG) on intestinal mucosal barrier damage in antibiotics and Lipopolysaccharide (LPS)-induced mice.

Methods

We established a composite mouse model by inducing intestinal mucosal barrier damage using antibiotics and LPS. The animals were divided into five groups: Control (normal and model) and experimental (low, medium, and high-dose ZG treatments). We evaluated the intestinal mucosal barrier using various methods, including monitoring body weight and fecal changes, assessing pathological damage and ultrastructure of the mouse ileum, analyzing expression levels of tight junction (TJ)-related proteins and genes, confirming the TLR4/NF-κB signaling pathway, and examining the structure of the intestinal flora.

Results

In mice, the dual induction of antibiotics and LPS led to weight loss, fecal abnormalities, disruption of ileocecal mucosal structure, increased intestinal barrier permeability, and disorganization of the microbiota structure. ZG restored body weight, alleviated diarrheal symptoms and pathological damage, and maintained the structural integrity of intestinal epithelial cells (IECs). Additionally, ZG reduced intestinal mucosal permeability by upregulating TJ-associated proteins (ZO-1, Occludin, Claudin-1, and JAM-A) and downregulating MLCK, thereby repairing intestinal mucosal barrier damage induced by dual induction of antibiotics and LPS. Moreover, ZG suppressed the TLR4/NF-κB signaling pathway, demonstrating anti-inflammatory properties and preserving barrier integrity. Furthermore, ZG restored gut microbiota diversity and richness, evidenced by increased Shannon and Observed features indices, and decreased Simpson's index. ZG also modulated the relative abundance of beneficial human gut bacteria (Bacteroidetes, Firmicutes, Verrucomicrobia, Parabacteroides, Lactobacillus, and Akkermansia) and harmful bacteria (Proteobacteria and Enterobacter), repairing the damage induced by dual administration of antibiotics and LPS.

Conclusion

ZG attenuates the dual induction of antibiotics and LPS-induced intestinal barrier damage and also protects the intestinal barrier function in mice.

Contribution of zinc accumulation to ischemic brain injury and its mechanisms about oxidative stress, inflammation, and autophagy: an update

Ischemic stroke is a leading cause of death and disability worldwide, and presently, there is no effective neuroprotective therapy. Zinc is an essential trace element that plays important physiological roles in the central nervous system. Free zinc concentration is tightly regulated by zinc-related proteins in the brain under normal conditions. Disruption of zinc homeostasis, however, has been found to play an important role in the mechanism of brain injury following ischemic stroke. A large of free zinc releases from storage sites after cerebral ischemia, which affects the functions and survival of nerve cells, including neurons, astrocytes, and microglia, resulting in cell death. Ischemia-triggered intracellular zinc accumulation also disrupts the function of blood-brain barrier via increasing its permeability, impairing endothelial cell function, and altering tight junction levels. Oxidative stress and neuroinflammation have been reported to be as major pathological mechanisms in cerebral ischemia/reperfusion injury. Studies have showed that the accumulation of intracellular free zinc could impair mitochondrial function to result in oxidative stress, and form a positive feedback loop between zinc accumulation and reactive oxygen species production, which leads to a series of harmful reactions. Meanwhile, elevated intracellular zinc leads to neuroinflammation. Recent studies also showed that autophagy is one of the important mechanisms of zinc toxicity after ischemic injury. Interrupting the accumulation of zinc will reduce cerebral ischemia injury and improve neurological outcomes. This review summarizes the role of zinc toxicity in cellular and tissue damage following cerebral ischemia, focusing on the mechanisms about oxidative stress, inflammation, and autophagy.

Endogenous Zinc-Ion-Triggered In Situ Gelation Enables Zn Capture to Reprogram Benign Hyperplastic Prostate Microenvironment and Shrink Prostate

Benign prostatic hyperplasia (BPH) as the leading cause of urination disorder is still a refractory disease, and there have no satisfied drugs or treatment protocols yet. With identifying excessive Zn2+ , inflammation, and oxidative stress as the etiology of aberrant hyperplasia, an injectable sodium alginate (SA) and glycyrrhizic acid (GA)-interconnected hydrogels (SAGA) featuring Zn2+ -triggered in situ gelation are developed to load lonidamine for reprogramming prostate microenvironment and treating BPH. Herein, SAGA hydrogels can crosslink with Zn2+ in BPH via coordination chelation and switch free Zn2+ to bound ones, consequently alleviating Zn2+ -arisen inflammation and glycolysis. Beyond capturing Zn2+ , GA with intrinsic immunoregulatory property can also alleviate local inflammation and scavenge reactive oxygen species (ROS). Intriguingly, Zn2+ chelation-bridged interconnection in SAGA enhances its mechanical property and regulates the degradation rate to enable continuous lonidamine release, favoring hyperplastic acini apoptosis and further inhibiting glycolysis. These multiple actions cooperatively reprogram BPH microenvironment to alleviate characteristic symptoms of BPH and shrink prostate. RNA sequencing reveals that chemotaxis, glycolysis, and tumor necrosis factor (TNF) inflammation-related pathways associated with M1-like phenotype polarization are discerned as the action rationales of such endogenous Zn2+ -triggered in situ hydrogels, providing a candidate avenue to treat BPH.

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.

Potential Role of Natural Antioxidants in Countering Reperfusion Injury in Acute Myocardial Infarction and Ischemic Stroke

Stroke and acute myocardial infarction are leading causes of mortality worldwide. The latter accounts for approximately 9 million deaths annually. In turn, ischemic stroke is a significant contributor to adult physical disability globally. While reperfusion is crucial for tissue recovery, it can paradoxically exacerbate damage through oxidative stress (OS), inflammation, and cell death. Therefore, it is imperative to explore diverse approaches aimed at minimizing ischemia/reperfusion injury to enhance clinical outcomes. OS primarily arises from an excessive generation of reactive oxygen species (ROS) and/or decreased endogenous antioxidant potential. Natural antioxidant compounds can counteract the injury mechanisms linked to ROS. While promising preclinical results, based on monotherapies, account for protective effects against tissue injury by ROS, translating these models into human applications has yielded controversial evidence. However, since the wide spectrum of antioxidants having diverse chemical characteristics offers varied biological actions on cell signaling pathways, multitherapy has emerged as a valuable therapeutic resource. Moreover, the combination of antioxidants in multitherapy holds significant potential for synergistic effects. This study was designed with the aim of providing an updated overview of natural antioxidants suitable for preventing myocardial and cerebral ischemia/reperfusion injuries.

High Dietary Zinc Intake Is Associated with Shorter Leukocyte Telomere Length, Mediated by Tumor Necrosis Factor-α: A Study of China Adults

OBJECTIVES

Diet can influence peripheral leukocyte telomere length (LTL), and various micronutrients have been reported to correlate with it. Zinc is known for its antioxidant properties and immunomodulatory effects. However, there are few epidemiological investigations on the relationship between dietary zinc intake and LTL. This study analyzed the association between dietary zinc and LTL and the potential role of inflammation and oxidative stress among them.

DESIGN

Cross-sectional and community-based study.

SETTING AND PARTICIPANTS

599 participants from rural communities in the Changping suburb of Beijing, China, were recruited.

MEASUREMENTS

Serum lipid profile, glycosylated hemoglobin (HbA1c), oxidative stress marker, and inflammatory cytokines levels were measured. Detailed dietary data were obtained using a 24 h food recall. LTL was assessed using a real-time PCR assay. Spearman analysis, restricted cubic splines (RCS), and general linear regression models were used to determine the association between dietary zinc intake and LTL. Simple regulatory models were also applied to analyze the role of inflammation and oxidative stress among them.

RESULTS

A total of 482 subjects were ultimately included in this analysis. Spearman analysis showed that dietary zinc intake and zinc intake under energy density were negatively correlated with LTL (r=-0.142 and -0.126, all P <0.05) and positively correlated with tumor necrosis factor-α (TNF-α) (r=0.138 and 0.202, all P <0.05) while only dietary zinc without energy adjustment had a positive correlation with superoxide dismutase (SOD). RCS (P for non-linearity=0.933) and multiple linear regression (B=-0.084, P=0.009) indicated a negative linear association between dietary zinc and LTL. The adjustment of TNF-α rather than SOD could abolish the relationship. The mediation model suggested that the unfavorable effect of dietary zinc on LTL was mediated by TNF-α.

CONCLUSIONS

High dietary zinc may correlate with telomere attrition, and TNF-α can act as a mediator in this relationship. In the future, more extensive cohort studies are needed to further explore the relationship between dietary zinc and cellular aging and the specific mechanisms.