Synergistic effects of lipopolysaccharide and rotenone on dopamine neuronal damage in rats

CD11b-NOX2 mutual regulation-mediated microglial exosome release contributes to rotenone-induced inflammation and neurotoxicity in BV2 microglia and primary cultures

Epidemiological studies have revealed a potent association between chronic exposure to rotenone, a commonly used pesticide, in individuals and the incidence of Parkinson's disease (PD). We previously identified the contribution of the activation of microglial NADPH oxidase (NOX2) in rotenone-induced neurotoxicity. However, the regulation of NOX2 activation remains unexplored. Integrins are known to be bidirectionally regulated in the plasma membrane through the inside-out and outside-in signaling. CD11b is the α-chain of integrin macrophage antigen complex-1. This study aimed to investigate whether CD11b mediates rotenone-induced NOX2 activation. We observed that rotenone exposure increased NOX2 activation in BV2 microglia, which was associated with elevated CD11b expression. Silencing CD11b significantly reduced rotenone-induced ROS production and p47phox phosphorylation, a key step for NOX2 activation. Furthermore, the Src-FAK-PKB and Syk-Vav1-Rac1 signaling pathways downstream of CD11b were found to be essential for CD11b-mediated NOX2 activation in rotenone-intoxicated microglia. Interestingly, we also found that inhibition of NOX2 decreased rotenone-induced CD11b expression, indicating a crosstalk between CD11b and NOX2. Subsequently, the inhibition of the CD11b-NOX2 axis suppressed rotenone-induced microglial activation and exosome release. Furthermore, inhibiting exosome synthesis in microglia blocked rotenone-induced gene expression of proinflammatory factors and related neurotoxicity. Finally, blocking the CD11b-NOX2 axis and exosome synthesis or endocytosis mitigated microglial activation and dopaminergic neurodegeneration in rotenone-intoxicated midbrain primary cultures. Our findings highlight the crucial involvement of the CD11b-NOX2 axis in rotenone-induced inflammation and neurotoxicity, offering fresh perspectives on the underlying mechanisms of pesticide-induced neuronal damage.

Selective microRNA expression of exosomes from retinal pigment epithelial cells by oxidative stress

The function of exosomal miRNAs (miRs) in retinal degeneration is largely unclear. We were aimed to investigate the functions of exosomes as well as their miRs derived from retinal pigment epithelial (RPE) cells following exposure to oxidative stress (OS). After the OS by lipopolysaccharide and rotenone on RPE cells, interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), Tumor Necrosis Factor-alpha (TNF-α) were upregulated, along with the decreased mitochondrial membrane potential and upregulated oxidative damage marker 8-OH-dG in RPE cells. RPE-derived exosomes were then isolated, identified, injected into the subretinal space in mice. After subretinal injection, RPE-exosomes after OS not only induced higher ROS level and apoptotic retinal cells, but also elevated IL-1β, IL-6 alongside TNF-α expressions among retina/RPE/choroidal complex. Next, miRs inside the exosomes were sequenced by the next generation sequencing (NGS) technology. NGS revealed that certain miRs were abundant in exosomes, while others were selectively kept by RPE cells. Further, downregulated miRs, like miR-125b-5p, miR-125a-5p, alongside miR-128-3p, and upregulated miR, such as miR-7-5p were validated byRT-qPCR. Finally, Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were used to find the possible target genes of those selective exosomal miRs. Our results proved that the RPE-derived exosomes after OS selectively express certain miRs, providing novel insights into the pathogenesis of age-related macular degeneration (AMD) in future.

Helicobacter pylori infection and Parkinson's Disease: etiology, pathogenesis and levodopa bioavailability

Parkinson's disease (PD), a neurodegenerative disorder with an unknown etiology, is primarily characterized by the degeneration of dopamine (DA) neurons. The prevalence of PD has experienced a significant surge in recent years. The unidentified etiology poses limitations to the development of effective therapeutic interventions for this condition. Helicobacter pylori (H. pylori) infection has affected approximately half of the global population. Mounting evidences suggest that H. pylori infection plays an important role in PD through various mechanisms. The autotoxin produced by H. pylori induces pro-inflammatory cytokines release, thereby facilitating the occurrence of central inflammation that leads to neuronal damage. Simultaneously, H. pylori disrupts the equilibrium of gastrointestinal microbiota with an overgrowth of bacteria in the small intestinal known as small intestinal bacterial overgrowth (SIBO). This dysbiosis of the gut flora influences the central nervous system (CNS) through microbiome-gut-brain axis. Moreover, SIBO hampers levodopa absorption and affects its therapeutic efficacy in the treatment of PD. Also, H. pylori promotes the production of defensins to regulate the permeability of the blood-brain barrier, facilitating the entry of harmful factors into the CNS. In addition, H. pylori has been found to induce gastroparesis, resulting in a prolonged transit time for levodopa to reach the small intestine. H. pylori may exploit levodopa to facilitate its own growth and proliferation, or it can inflict damage to the gastrointestinal mucosa, leading to gastrointestinal ulcers and impeding levodopa absorption. Here, this review focused on the role of H. pylori infection in PD from etiology, pathogenesis to levodopa bioavailability.