Parkinson’s disease (PD) is a gradually progressing neurodegenerative condition that is marked by a loss of motor coordination along with non-motor features. Although the precise cause of PD has not been determined, the disease condition is mostly associated with the exposure to environmental toxins, such as metals, and their abnormal accumulation in the brain. Heavy metals, such as iron (Fe), mercury (Hg), manganese (Mn), copper (Cu), and lead (Pb), have been linked to PD and contribute to its progression. In addition, the interactions among the components of a metal mixture may result in synergistic toxicity. Numerous epidemiological studies have demonstrated a connection between PD and either single or mixed exposure to these heavy metals, which increase the prevalence of PD. Chronic exposure to heavy metals is related to the activation of proinflammatory cytokines resulting in neuronal loss through neuroinflammation. Similarly, metals disrupt redox homeostasis while inducing free radical production and decreasing antioxidant levels in the substantia nigra. Furthermore, these metals alter molecular processes and result in oxidative stress, DNA damage, mitochondrial dysfunction, and apoptosis, which can potentially trigger dopaminergic neurodegenerative disorders. This review focuses on the roles of Hg, Pb, Mn, Cu, and Fe in the development and progression of PD. Moreover, it explores the plausible roles of heavy metals in neurodegenerative mechanisms that facilitate the development of PD. A better understanding of the mechanisms underlying metal toxicities will enable the establishment of novel therapeutic approaches to prevent or cure PD.

Humans are exposed to lead (Pb), mercury (Hg), and cadmium (Cd) through various routes, including drinking water, and such exposure can lead to a range of toxicological effects. However, few studies have investigated the toxic effects of exposure to mixtures of metals, particularly in relation to neurotoxicity. In this study, 7-week-old male mice were exposed to Pb, Hg, and Cd individually or in combination through their drinking water for 28 days. The mice exposed to the metal mixture exhibited significantly reduced motor coordination and impaired learning and memory abilities compared to the control group and each of the single metal exposure groups, indicating a higher level of neurotoxicity of the metal mixture. The dopamine content in the striatum was significantly lower in the metal mixture exposure group than in the single metal exposure groups and the control group. Furthermore, compared to the control group, the metal mixture exposure group showed a significantly lower expression level of tyrosine hydroxylase (TH) and significantly higher expression levels of dopamine transporter (DAT), tryptophan hydroxylase 1 (TPH1), and serotonin reuptake transporter (SERT). Notably, there were no significant differences in SERT expression between the single metal exposure groups and the control group, but SERT expression was significantly higher in the metal mixture exposure group than in the single metal and control groups. These findings suggest that the key proteins involved in the synthesis and reuptake of dopamine (TH and DAT, respectively), as well as in the synthesis and reuptake of serotonin (TPH1 and SERT, respectively), play crucial roles in the neurotoxic effects associated with exposure to metal mixtures. In conclusion, this study demonstrates that simultaneous exposure to different metals can impact key enzymes involved in dopaminergic and serotonergic neurotransmission processes, leading to disruptions in dopamine and serotonin homeostasis and consequently a range of detrimental neurobehavioral effects.

Environmental exposure to arsenic (As), lead (Pb), and cadmium (Cd) frequently occurs; however, data on the specific effects of combined exposure on neurotransmission, specifically dopaminergic neurotransmission, are lacking. In this study, motor coordination and dopamine content, along with the expression of tyrosine hydroxylase (TH), dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2), and dopamine receptors (DRs), were examined in the striatum of adult male mice following exposure to drinking water containing As, Pb, and/or Cd. We found that exposure to a metal mixture impaired motor coordination. After 4 weeks of treatment, a significant decrease in dopamine content and expression of TH, DAT, and VMAT2 was observed in the striatum of metal-mixture-treated mice, compared to the controls or single-metal-exposed groups. However, DRD1 and DRD2 expression did not significantly change with metal treatment. These results suggest that altered dopaminergic neurotransmission by the collective action of metals may contribute to metal-mixture-induced neurobehavioral disorders.

Background/Objectives: Semaglutide, a glucagon-like peptide-1 receptor (GLP-1R) agonist, is a well-established pharmacologic agent for inducing weight loss in individuals with obesity and is prescribed regardless of type 2 diabetes mellitus (DM) status. However, it remains unclear whether the weight-lowering efficacy of semaglutide differs significantly between individuals with and without DM. To address this question, we conducted a systematic review and meta-analysis comparing the effects of once-weekly subcutaneous semaglutide at 2.4 mg on weight loss in adults with and without DM. Methods: A comprehensive literature search was performed using the PubMed database to identify randomized controlled trials (RCTs) involving overweight or obese adults receiving semaglutide at 2.4 mg weekly for 40 to 70 weeks. Using a random-effects model, we estimated the weighted mean differences in body weight reduction between the two groups. Nine RCTs met the inclusion criteria, among which two provided subgroup data for participants with and without DM within the same trial population. Registration number in PROSPERO: CRD420251077610. Results: In participants with DM (n = 4 studies), semaglutide was associated with a weighted mean body weight reduction of −6.34% (95% confidence interval: −6.98 to −5.69), with negligible heterogeneity across studies (I² = 0.0%). By contrast, among participants without DM (n = 7 studies), the weighted estimate of weight loss was −11.57% (95% confidence interval: −12.94 to −10.19), with moderate heterogeneity observed (I² = 63.6%). Conclusions: The observed difference in weight loss efficacy between the groups was clinically meaningful. While once-weekly semaglutide at 2.4 mg elicited significant weight loss in both populations, the magnitude of effect was notably greater in those without DM. This disparity may be explained by metabolic characteristics frequently present in individuals with DM, such as insulin resistance, hyperinsulinemia, and compensatory mechanisms related to glycemic control.

The mechanical elasticity of lipid nanoparticles (LNPs) is crucial to their pharmaceutical performance. This study investigates how the mechanical interactions between LNPs, target cells, and macrophages affect the internalization of LNPs into target cells at tumor sites. According to our bio‐mechanical study, drug‐resistant breast cancer cells are stiffer than sensitive ones, while invasive cells are softer; similarly, protumoral M2 macrophages are softer than M1 macrophages. Softer LNPs show increased cellular uptake in breast cancer cells and macrophages, with enhanced engulfment in invasive cells and M2 macrophages. Additionally, the presence of M2 macrophages promotes greater LNP internalization by cancer cells, facilitating the malignant and invasive nature of cancer cells. In addition, because breast cancer cells engulf LNPs via an energy‐efficient fusion pathway but LNPs in macrophages undergo clathrin‐mediated endocytosis, LNPs are internalized more into cancer cells but not into M2. In orthotopic tumor models, softer LNPs penetrate tumors quickly, enhancing suppression, whereas stiffer LNPs permeate slowly but show prolonged retention in stiffer tumors, supporting antitumor efficacy with repeated dosing. These findings underscore the importance of mechanical interactions between LNPs, target cells, and macrophages in optimizing LNP delivery systems, offering insights for more effective designs.