Inhibition of LOX-1 prevents inflammation and photoreceptor cell death in retinal degeneration

The OLR1/NF-κB feedback loop exacerbates HIV-1 Tat-induced microglial inflammatory response and neuronal apoptosis

Oxidized low density lipoprotein receptor 1 (OLR1), a type II integral membrane glycoprotein, is involved in multiple neurological diseases. However, the roles and mechanisms of OLR1 in HIV-associated neurocognitive disorder (HAND) remain unclear. In the central nervous system, Transactivator of transcription (Tat) induces inflammatory response in microglia, thereby leading to neuronal apoptosis. In the present study, we demonstrated that OLR1 expression was upregulated during ectopic expression of Tat or soluble Tat stimulus in BV-2 microglial cells. Moreover, OLR1 signaling was proved to facilitate Tat-triggered inflammatory response and alleviated the microglia-derived conditioned media-mediated HT-22 neural cells apoptosis in a NF-κB-dependent manner. Conversely, Tat augmented OLR1 expression via NF-κB signaling pathway. Finally, in mouse models, we determined that silencing of OLR1 significantly ameliorated Tat‑induced neuroinflammation and hippocampal neuronal death. Taken together, our study clarifies the potential role of the OLR1/NF-κB feedback loop in Tat-induced microglial inflammatory response and neuronal apoptosis, which could be a novel therapeutic target for relief of HAND.

Suppression of astrocyte elevated gene-1 protects against light-induced photoreceptor apoptosis and inflammation in retina

PURPOSE

To research the function of astrocyte elevated gene-1 (AEG-1) in light-induced retinal degeneration.

METHODS

The retinas of BALB/c mice and 661W cells damage were induced by exposure to light; Lipopolysaccharide (LPS) was used to stimulate BV2 cells. AEG-1 siRNA transfection was used to inhibit AEG-1. Expressions of AEG-1, TLR4, TNF-α, phosphor-NF-κB (p-NF-κB) and total NF-κB (t-NF-κB) were detected. Photoreceptor apoptosis was evaluated by flow cytometry or TUNEL. Histological analyses were performed by hematoxylin and eosin (HE) staining.

RESULTS

AEG-1 was highly expressed in light damaged (LD) retinas. The photoreceptor apoptosis and the thinning of outer nuclear layer (ONL) were inhibited by AEG-1 siRNA in LD mice retinas. The AEG-1 siRNA pretreatment significantly down-regulated the elevated expression levels of TLR4, p-NF-κB and TNF-α induced by LD in retinas. In vitro, AEG-1 was upregulated in 661W cells induced by LD and in BV2 cells stimulated by LPS. The AEG-1 siRNA prevented light induced apoptosis of 661W cells, and down-regulated the elevated expressions of TLR4, p-NF-κB and pro-inflammatory cytokine TNF-α caused by LPS in BV2 cells.

CONCLUSIONS

AEG-1 is highly expressed in retinal degeneration caused by LD. Suppression of AEG-1 protects against photoreceptor apoptosis and rescues the thinning of ONL in LD retinas. Suppression of AEG-1 also diminishes inflammation in light induced retinal degeneration, which may be regulated through the NF-κB pathway. Therefore, AEG-1 perhaps become a potential therapeutic target for this type of retinal degenerative disease.

Oxidative Stress and Inflammation-Related mRNAs Are Elevated in Serum of a Finnish Wet AMD Cohort

Purpose

Localized diseases can be affected by and affect the systemic environment via blood circulation. In this study, we explored the differences in circulating serum mRNAs between patients with wet AMD (wAMD) and controls.

Methods

Blood samples were obtained from 60 Finnish patients with wAMD and 64 controls. After serum preparation and RNA sequencing, the count data was examined for differentially expressed genes (DEGs) and further checked for enriched molecular pathways and ontology terms as well as links to clinical data.

Results

We found many DEGs and some enriched pathways, including the inflammation and cell survival-associated pathway tumour necrosis factor alpha (TNF-α) signaling via nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). The related DEGs were oxidized low-density lipoprotein receptor 1 (OLR1), salt inducible kinase 1 (SIK1), and coagulation factor III (F3). DEGs from degradative macular and retinal processes were also examined, many of which were also related to cardiovascular disease and maintenance. Additionally, DEG counts were inspected in relation to clinical and anti-VEGF treatment parameters, and glutamine amidotransferase-like class 1 domain-containing 3A (GATD3A) levels were found to be significantly lower in patients with wAMD treated with anti-VEGF.

Conclusions

Differentially expressed systemic mRNAs that are linked to mitochondrial function, oxidative stress, and inflammation may have a role in the pathology of wAMD. Our observations provide new data for the understanding of the progression of wAMD.

Quercetin Regulates Microglia M1/M2 Polarization and Alleviates Retinal Inflammation via ERK/STAT3 Pathway

Retinal inflammation is a pivotal characteristic observed in various retinal degenerative disorders, notably age-related macular degeneration (AMD), primarily orchestrated by the activation of microglia. Targeting the inhibition of microglial activation has emerged as a therapeutic focal point. Quercetin (Qu), ubiquitously present in dietary sources and tea, has garnered attention for its anti-neuroinflammatory properties. However, the impact of Qu on retinal inflammation and the associated mechanistic pathways remains incompletely elucidated. In this study, retinal inflammation was induced in adult male C57BL/6 J mice through intraperitoneal administration of LPS. The results revealed that Qu pre-treatment induces a phenotypic shift in microglia from M1 phenotype to M2 phenotype. Furthermore, Qu attenuated retinal inflammation and stabilized the integrity of the blood-retina barrier (BRB). In vitro experiments revealed that Qu impedes microglial activation, proliferation, and migration, primarily via modulation the ERK/STAT3 signaling pathway. Notably, these actions of Qu significantly contributed to the preservation of photoreceptors. Consequently, Qu pre-treatment holds promise as an effective strategy for controlling retinal inflammation and preserving visual function.

Characterization of Ocular Morphology in Col4a3-/- Mice as a Murine Model for Alport Syndrome

Purpose

The purpose of this study was to investigate the ocular morphological characteristics of Col4a3-/- mice as a model of Alport syndrome (AS) and the potential pathogenesis.

Methods

The expression of collagen IV at 8, 12, and 21 weeks of age was evaluated by immunohistochemistry in wild-type (WT) and Col4a3-/- mice. Hematoxylin and eosin (H&E) staining and thickness measurements were performed to assess the thickness of anterior lens capsule and retina. Ultrastructure analysis of corneal epithelial basement membrane, anterior lens capsule, internal limiting membrane (ILM), and retinal pigment epithelium (RPE) basement membrane was performed using transmission electron microscopy. Finally, Müller cell activation was evaluated by glial fibrillary acidic protein (GFAP) expression.

Results

Collagen IV was downregulated in the corneal epithelial basement membrane and ILM of Col4a3-/- mice. The hemidesmosomes of Col4a3-/- mice corneal epithelium became flat and less electron-dense than those of the WT group. Compared with those of the WT mice, the anterior lens capsules of Col4a3-/- mice were thinner. Abnormal structure was detected at the ILM Col4a3-/- mice, and the basal folds of the RPE basement membrane in Col4a3-/- mice were thicker and shorter. The retinas of Col4a3-/- mice were thinner than those of WT mice, especially within 1000 µm away from the optic nerve. GFAP expression enhanced in each age group of Col4a3-/- mice.

Conclusions

Our results suggested that Col4a3-/- mice exhibit ocular anomalies similar to patients with AS. Additionally, Müller cells may be involved in AS retinal anomalies.

Translational Relevance

This animal model could provide an opportunity to understand the underlying mechanisms of AS ocular disorders and to investigate potential new treatments.

Quercetin Inhibits Neuronal Pyroptosis and Ferroptosis by Modulating Microglial M1/M2 Polarization in Atherosclerosis

Atherosclerosis (AS) with iron and lipid overload and systemic inflammation is a risk factor for Alzheimer's disease. M1 macrophage/microglia participate in neuronal pyroptosis and recently have been reported to be the ferroptosis-resistant phenotype. Quercetin plays a prominent role in preventing and treating neuroinflammation, but the protective mechanism against neurodegeneration caused by iron deposition is poorly understood. ApoE-/- mice were fed a high-fat diet with or without quercetin treatment. The Morris water maze and novel object recognition tests were conducted to assess spatial learning and memory, and nonspatial recognition memory, respectively. Prussian blue and immunofluorescence staining were performed to assess the iron levels in the whole brain and in microglia, microglia polarization, and the degree of microglia/neuron ferroptosis. In vitro, we further explored the molecular biological alterations associated with microglial polarization, neuronal pyroptosis, and ferroptosis via Western blot, flow cytometry, CCK8, LDH, propidium iodide, and coculture system. We found that quercetin improved brain lesions and spatial learning and memory in AS mice. Iron deposition in the whole brain or microglia was reversed by the quercetin treatment. In the AS group, the colocalization of iNOS with Iba1 was increased, which was reversed by quercetin. However, the colocalization of iNOS with PTGS2/TfR was not increased in the AS group, suggesting a character resisting ferroptosis. Quercetin induced the expression of Arg-1 and decreased the colocalizations of Arg-1 with PTGS2/TfR. In vitro, ox-LDL combined with ferric ammonium citrate treatment (OF) significantly shifted the microglial M1/M2 phenotype balance and increased the levels of free iron, ROS, and lipid peroxides, which was reversed by quercetin. M1 phenotype induced by OF caused neuronal pyroptosis and was promoted to ferroptosis by L-NIL treatment, which contributed to neuronal ferroptosis as well. However, quercetin induced the M1 to M2 phenotype and inhibited M2 macrophages/microglia and neuron pyroptosis or ferroptosis. In summary, quercetin alleviated neuroinflammation by inducing the M1 to M2 phenotype to inhibit neuronal pyroptosis and protected neurons from ferroptosis, which may provide a new idea for neuroinflammation prevention and treatment.

Intravitreal injection of mitochondrial DNA induces cell damage and retinal dysfunction in rats

Background

Retinal neurodegeneration is induced by a variety of environmental insults and stresses, but the exact mechanisms are unclear. In the present study, we explored the involvement of cytosolic mitochondrial DNA (mtDNA), resulting in the cGAS-STING dependent inflammatory response and apoptosis in retinal damage in vivo.

Methods

Retinal injury was induced with white light or intravitreal injection of lipopolysaccharide (LPS). After light- or LPS-induced injury, the amount of cytosolic mtDNA in the retina was detected by PCR. The mtDNA was isolated and used to transfect retinas in vivo. WB and real-time PCR were used to evaluate the activation of cGAS-STING pathway and the levels of apoptosis-associated protein at different times after mtDNA injection. Retinal cell apoptosis rate was detected by TUNEL staining. Full-field electroretinography (ERG) was used to assess the retinal function.

Results

Light injury and the intravitreal injection of LPS both caused the leakage of mtDNA into the cytoplasm in retinal tissue. After the transfection of mtDNA in vivo, the levels of cGAS, STING, and IFN-β mRNAs and the protein levels of STING, phosph-TBK1, phospho-IRF3, and IFN-β were upregulated. mtDNA injection also induced the activation of caspase 3 and caspase 9. BAX and BAK were increased at both the mRNA and protein levels. The release of cytochrome c from the mitochondria to the cytosol was increased after mtDNA injection. The wave amplitudes on ERG decreased and retinal cell apoptosis was detected after mtDNA injection.

Conclusions

Cytosolic mtDNA triggers an inflammatory response. It also promotes apoptosis and the dysfunction of the retina.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-022-00390-6.

Investigation of indole functionalized pyrazoles and oxadiazoles as anti-inflammatory agents: Synthesis, in-vivo, in-vitro and in-silico analysis

There are several potential side and adverse effects are found to be associated with the anti-inflammatory drugs in clinical practice. The long-term use of these clinical agents highly unsafe. It encouraged the development of novel heterocyclic compounds with potential anti-inflammatory activity and low to no toxicity. In present investigation, a total of 12 indole functionalized pyrazole and oxadiazole derivatives were designed, synthesized and evaluated for the in-vivo anti-inflammatory and analgesic potential. These compounds displayed comparable anti-inflammatory and analgesic potential to the reference drugs. Finally, molecular docking analysis was performed considering different anti-inflammatory targets to determine the mechanistic target of the designed molecules. Detailed analysis suggested that the molecules inhibit COX-2, preferably over other anti-inflammatory targets. The results suggested that two compounds (15c and 15f) were found promising candidates for the development of novel anti-inflammatory agents.