HMGB2 causes photoreceptor death via down-regulating Nrf2/HO-1 and up-regulating NF-κB/NLRP3 signaling pathways in light-induced retinal degeneration model

The negative feedback loop of NF-κB/miR-202-5p/HMGB2 attenuates sepsis induced acute kidney injury

Sepsis represents a primary cause of acute kidney injury (AKI), yet the underlying mechanisms of septic AKI remain poorly understood. Thus, there exists an urgent need for a deeper understanding of its underlying mechanisms and the development of effective therapeutic strategies. Our study reveals a notable induction in microRNA-202-5p (miR-202-5p) levels within renal tubular cells in septic AKI both in vivo and in vitro models. Treatment of renal tubular cells with LPS induced NF-κB activation, which was linked to the induction of miR-202-5p. ChIP assays confirmed NF-κB binding to the miR-202-5p gene promoter upon LPS stimulation. Functionally, miR-202-5p mimics attenuated tubular cell death, kidney injury, and intra-renal inflammatory cytokine production, whereas inhibition of miR-202-5p conferred injurious effects in septic AKI. Notably, miR-202-5p suppressed the expression of High Mobility Group Box 2 (HMGB2) in both in vitro and in vivo septic AKI models. Luciferase microRNA target assays further validated HMGB2 as a direct target of miR-202-5p. Knockdown of HMGB2 inhibits LPS-induced NF-κB activation in septic AKI, as evidenced by HMGB2 siRNA transfection significantly inhibited the nuclear translocation of NF-κB. Together, these findings elucidate the NF-κB/miR-202-5p/HMGB2 negative feedback loop which can attenuate kidney injury by inhibiting renal inflammation in septic AKI. Our findings open new avenues for developing targeted therapies to manage septic AKI effectively.

Retinal light damage: From mechanisms to protective strategies

Visible light serves as a crucial medium for vision formation.;however, prolonged or excessive exposure to light is recognized as a significant etiological factor contributing to retinal degenerative diseases. The retina, with its unique structure and adaptability, relies on the homeostasis of cellular functions to maintain visual health. Under normal conditions, the retina can mount adaptive responses to various insults, including light-induced damage. Unfortunately, exposure to intense and excessive light triggers a cascade of pathological alterations in retinal photoreceptor cells, pigment epithelial cells, ganglion cells, and glial cells. These alterations encompass disruption of intracellular REDOX and Ca²⁺ homeostasis, pyroptosis, endoplasmic reticulum stress, autophagy, and the release of inflammatory cytokines, culminating in irreversible retinal damage. We first delineate the mechanisms of retinal light damage through 4 main avenues: mitochondria function, endoplasmic reticulum stress, cell autophagy, and inflammation. Subsequently, we discuss protective strategies against retinal light damage, aiming to guide research toward the prevention and treatment of light-induced retinal conditions.

Retinal proteome profiling of inherited retinal degeneration across three different mouse models suggests common drug targets in retinitis pigmentosa

Inherited retinal degenerations (IRDs) are a leading cause of blindness among the population of young people in the developed world. Approximately half of IRDs initially manifest as gradual loss of night vision and visual fields, characteristic of retinitis pigmentosa (RP). Due to challenges in genetic testing, and the large heterogeneity of mutations underlying RP, targeted gene therapies are an impractical largescale solution in the foreseeable future. For this reason, identifying key pathophysiological pathways in IRDs that could be targets for mutation-agnostic and disease-modifying therapies (DMTs) is warranted. In this study, we investigated the retinal proteome of three distinct IRD mouse models, in comparison to sex- and age-matched wild-type mice. Specifically, we used the Pde6βRd10 (rd10) and RhoP23H/WT (P23H) mouse models of autosomal recessive and autosomal dominant RP, respectively, as well as the Rpe65-/- mouse model of Leber´s congenital amaurosis type 2 (LCA2). The mice were housed at two distinct institutions and analyzed using LC-MS in three separate facilities/instruments following data-dependent and data-independent acquisition modes. This cross-institutional and multi-methodological approach signifies the reliability and reproducibility of the results. The largescale profiling of the retinal proteome, coupled with in vivo electroretinography recordings, provided us with a reliable basis for comparing the disease phenotypes and severity. Despite evident inflammation, cellular stress, and downscaled phototransduction observed consistently across all three models, the underlying pathologies of RP and LCA2 displayed many differences, sharing only four general KEGG pathways. The opposite is true for the two RP models in which we identify remarkable convergence in proteomic phenotype even though the mechanism of primary rod death in rd10 and P23H mice is different. Our data highlights the cAMP and cGMP second-messenger signaling pathways as potential targets for therapeutic intervention. The proteomic data is curated and made publicly available, facilitating the discovery of universal therapeutic targets for RP.

(+)-catechin protects PC12 cells against CORT-induced oxidative stress and pyroptosis through the pathways of PI3K/AKT and Nrf2/HO-1/NF-κB

Pyroptosis induced by oxidative stress is a significant contributor to mental health disorders, including depression (+)-Catechin (CA), a polyphenolic compound prevalent in various food sources, has been substantiated by prior research to exhibit potent antioxidant properties and potential antidepressant effects. Nonetheless, the precise antidepressive mechanisms and effects of CA remain incompletely elucidated. In this study, we employed corticosterone (CORT) and PC12 cells to develop a cellular model of depression, aiming to investigate the protective effects of CA against CORT-induced cellular damage. Our objective was to elucidate the underlying mechanisms of protective action. We utilized transcriptomic analysis to identify differentially expressed genes and employed bioinformatics approaches to predict the potential mechanisms of CA's protective effects in PC12 cells. These transcriptomic predictions were subsequently validated through western blot analysis. The findings indicated that CA possesses the capacity to mitigate oxidative stress and suppress pyroptosis in PC12 cells via the activation of the PI3K/AKT signaling pathway. This activation subsequently modulates the Nrf2/HO1/NF-κB pathways, thereby providing protection to PC12 cells against damage induced by CORT. Furthermore, we investigated the interaction between CA and the Keap1 protein employing molecular docking and protein thermal shift assays. We propose that CA can activate Nrf2 through two mechanisms to decrease reactive oxygen species (ROS) levels and inhibit pyroptosis: one mechanism involves the activation of the PI3K/AKT signaling pathway, and the other involves direct binding to Keap1, leading to an increase in p-Nrf2.

Meta-stable state photoacid containing β-estradiol fragment with photomodulated biological activity and anti-cancer stem cells properties

Photopharmacology is a young and rapidly developing field of research that offers significant potential for new insights into targeted therapy. While it primarily focuses on cancer treatment, it also holds promise for other diseases. The key feature of photopharmacological agents is the presence of a photosensitive and biologically active component in the same molecule. In our current study, we synthesized a spiropyran-based meta-stable state photoacid containing a fragment of β-estradiol. This compound exhibits negative photochromism and photocontrolled fluorescence under visible-light irradiation due to the initial stabilization of its self-protonated form in solution. We conducted comprehensive biological studies on the HeLa cells model to assess the short- and long-term cytotoxicity of the photoacid, its metabolic effects, its influence on signaling and epithelial-mesenchymal transition super-system pathways, and the proportion of the population enriched with cancer stem cells. Our findings reveal that this derivative demonstrates low cytotoxicity to HeLa cells, yet it is capable of dramatically reducing malignant cells side population enriched in cancer stem cells. Additionally, appropriate structural modification lead to an increase in some other biological effects compared to β-estradiol. In particular, our substance possesses rare properties of AP-1 suppression and demonstrates some pro-oxidant and metabolic effects, which can be regulated by visible light irradiation. As a result, the new estradiol-based photoacid may be considered a promising multi-acting photopharmacological agent for the next-generation anti-cancer research & development.

HMGB2 Release Promotes Pulmonary Hypertension and Predicts Severity and Mortality of Patients With Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary hypertension (PH) is a progressive and life-threatening disease characterized by pulmonary vascular remodeling, which involves aberrant proliferation and apoptosis resistance of the pulmonary arterial smooth muscle cells (PASMCs), resembling the hallmark characteristics of cancer. In cancer, the HMGB2 (high-mobility group box 2) protein promotes the pro-proliferative/antiapoptotic phenotype. However, the function of HMGB2 in PH remains uninvestigated.

METHODS

Smooth muscle cell (SMC)-specific HMGB2 knockout or HMGB2-OE (HMGB2 overexpression) mice and HMGB2 silenced rats were used to establish hypoxia+Su5416 (HySu)-induced PH mouse and monocrotaline-induced PH rat models, respectively. The effects of HMGB2 and its underlying mechanisms were subsequently elucidated using RNA-sequencing and cellular and molecular biology analyses. Serum HMGB2 levels were measured in the controls and patients with pulmonary arterial (PA) hypertension.

RESULTS

HMGB2 expression was markedly increased in the PAs of patients with PA hypertension and PH rodent models and was predominantly localized in PASMCs. SMC-specific HMGB2 deficiency or silencing attenuated PH development and pulmonary vascular remodeling in hypoxia+Su5416-induced mice and monocrotaline-treated rats. SMC-specific HMGB2 overexpression aggravated hypoxia+Su5416-induced PH. HMGB2 knockdown inhibited PASMC proliferation in vitro in response to PDGF-BB (platelet-derived growth factor-BB). In contrast, HMGB2 protein stimulation caused the hyperproliferation of PASMCs. In addition, HMGB2 promoted PASMC proliferation and the development of PH by RAGE (receptor for advanced glycation end products)/FAK (focal adhesion kinase)-mediated Hippo/YAP (yes-associated protein) signaling suppression. Serum HMGB2 levels were significantly increased in patients with PA hypertension, and they correlated with disease severity, predicting worse survival.

CONCLUSIONS

Our findings indicate that targeting HMGB2 might be a novel therapeutic strategy for treating PH. Serum HMGB2 levels could serve as a novel biomarker for diagnosing PA hypertension and determining its prognosis.

Cardiovascular Disease and miRNAs: Possible Oxidative Stress-Regulating Roles of miRNAs

MicroRNAs (miRNAs) have been highlighted as key players in numerous diseases, and accumulating evidence indicates that pathological expressions of miRNAs contribute to both the development and progression of cardiovascular diseases (CVD), as well. Another important factor affecting the development and progression of CVD is reactive oxygen species (ROS), as well as the oxidative stress they may impose on the cells. Considering miRNAs are involved in virtually every biological process, it is not unreasonable to assume that miRNAs also play critical roles in the regulation of oxidative stress. This narrative review aims to provide mechanistic insights on possible oxidative stress-regulating roles of miRNAs in cardiovascular diseases based on differentially expressed miRNAs reported in various cardiovascular diseases and their empirically validated targets that have been implicated in the regulation of oxidative stress.

PRMT7-Dependent Transcriptional Activation of Hmgb2 Aggravates Severe Acute Pancreatitis by Promoting Acsl1-Induced Ferroptosis

Severe acute pancreatitis (SAP) is a highly fatal abdominal emergency, and its association with protein arginine methyltransferase 7 (PRMT7), the sole known type III enzyme responsible for the monomethylation of arginine residue, remains unexplored. In this study, we observe an increase in the PRMT7 levels in the pancreas of SAP mice and Cerulein-LPS-stimulated AR42J cells. Overexpression of Prmt7 exacerbated pancreatic damage in SAP, while the inhibition of PRMT7 improved SAP-induced pancreatic damage. Furthermore, PRMT7 overexpression promoted inflammation, oxidative stress, and ferroptosis during SAP. Mechanically, PRMT7 catalyzed monomethylation at histone H4 arginine 3 (H4R3me1) at the promoter region of high mobility group proteins 2 (HMGB2), thereby enhancing its transcriptional activity. Subsequently, HMGB2 facilitated Acyl CoA synthase long-chain family member 1 (ACSL1) transcription by binding to its promoter region, resulting in the activation of ferroptosis. Inhibition of PRMT7 effectively alleviated ferroptosis in Cerulein-LPS-induced AR42J cells by suppressing the HMGB2-ACSL1 pathway. Overall, our study reveals that PRMT7 plays a crucial role in promoting SAP through its regulation of the HMGB2-ACSL1 pathway to accelerate ferroptosis.

Pyroptosis: Mechanisms and links with diabetic cardiomyopathy

Diabetes mellitus (DM) is a chronic metabolic disease characterized by hyperglycaemia that seriously affects human health. Diabetic cardiomyopathy (DCM) is a major cardiovascular complication and one of the main causes of death in patients with DM. Although DCM attracts great attention, and new therapeutic methods are continuously developed, there is a lack of effective treatment strategies. Therefore, exploring and targeting new signalling pathways related to the evolution of DCM becomes a hotspot and difficulty in the prevention and treatment of DCM. Pyroptosis is a newly discovered regulated cell death that is heavily dependent on the formation of plasma membrane pores by members of the gasdermin protein family and is reported to be involved in the occurrence, development, and pathogenesis of DCM. In this review, we focus on the molecular mechanisms of pyroptosis, its involvement in the relevant signalling pathways of DCM, and potential pyroptosis-targeting therapeutic strategies for the treatment of DCM. Our review provides new insights into the use of pyroptosis as a useful tool for the prevention and treatment of DCM and clarifies future research directions.

HMGB2 Deficiency Mitigates Abdominal Aortic Aneurysm by Suppressing Ang-II-Caused Ferroptosis and Inflammation via NF-κβ Pathway

Background

Ferroptosis is a new form of cell death, which is closely related to the occurrence of many diseases. Our work focused on the mechanism by which HMGB2 regulate ferroptosis and inflammation in abdominal aortic aneurysm (AAA).

Methods

Reverse transcription-quantitative polymerase chain reaction and western blot were utilized to assess HMGB2 levels. CCK-8 and flow cytometry assays were utilized to measure cell viability and apoptosis. We detected reactive oxygen species generation, Fe2+ level, and ferroptosis-related protein levels in Ang-II-treated VSMCs, which were typical characteristics of ferroptosis. Finally, the mice model of AAA was established to verify the function of HMGB2 in vivo.

Results

Increased HMGB2 level was observed in Ang-II-treated VSMCs and Ang-II-induced mice model. HMGB2 depletion accelerated viability and impeded apoptosis in Ang-II-irritatived VSMCs. Moreover, HMGB2 deficiency neutralized the increase of ROS in VSMCs caused by Ang-II. HMGB2 silencing considerably weakened Ang-II-caused VSMC ferroptosis, as revealed by the decrease of Fe2+ level and ACSL4 and COX2 levels and the increase in GPX4 and FTH1 levels. Furthermore, the mitigation effects of shHMGB2 on Ang-II-induced VSMC damage could be counteracted by erastin, a ferroptosis agonist. Mechanically, HMGB2 depletion inactivated the NF-κβ signaling in Ang-II-treated VSMCs.

Conclusions

Our work demonstrated that inhibition of HMGB2-regulated ferroptosis and inflammation to protect against AAA via NF-κβ signaling, suggesting that HMGB2 may be a potent therapeutic agent for AAA.

HMGB family proteins: Potential biomarkers and mechanistic factors in cardiovascular diseases

Cardiovascular disease (CVD) is the most fatal disease that causes sudden death, and inflammation contributes substantially to its occurrence and progression. The prevalence of CVD increases as the population ages, and the pathophysiology is complex. Anti-inflammatory and immunological modulation are the potential methods for CVD prevention and treatment. High-Mobility Group (HMG) chromosomal proteins are one of the most abundant nuclear nonhistone proteins which act as inflammatory mediators in DNA replication, transcription, and repair by producing cytokines and serving as damage-associated molecular patterns in inflammatory responses. The most common and well-studied HMG proteins are those with an HMGB domain, which participate in a variety of biological processes. HMGB1 and HMGB2 were the first members of the HMGB family to be identified and are present in all investigated eukaryotes. Our review is primarily concerned with the involvement of HMGB1 and HMGB2 in CVD. The purpose of this review is to provide a theoretical framework for diagnosing and treating CVD by discussing the structure and function of HMGB1 and HMGB2.

The Role of Nrf2/sMAF Signalling in Retina Ageing and Retinal Diseases

Age-related diseases, such as Parkinson's disease, Alzheimer's disease, cardiovascular diseases, cancers, and age-related macular disease, have become increasingly prominent as the population ages. Oxygen is essential for living organisms, but it may also cause disease when it is transformed into reactive oxygen species via biological processes in cells. Most of the production of ROS occurs in mitochondrial complexes I and III. The accumulation of ROS in cells causes oxidative stress, which plays a crucial role in human ageing and many diseases. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a key antioxidant transcription factor that plays a central role in many diseases and ageing in general. It regulates many downstream antioxidative enzymes when cells are exposed to oxidative stress. A basic-region leucine zipper (bZIP) transcription factor, MAF, specifically the small MAF subfamily (sMAFs), forms heterodimers with Nrf2, which bind with Maf-recognition elements (MAREs) in response to oxidative stress. The role of this complex in the human retina remains unclear. This review summarises the current knowledge about Nrf2 and its downstream signalling, especially its cofactor-MAF, in ageing and diseases, with a focus on the retina. Since Nrf2 is the master regulator of redox homeostasis in cells, we hypothesise that targeting Nrf2 is a promising therapeutic approach for many age-related diseases.

Structure and Functions of HMGB2 Protein

High-Mobility Group (HMG) chromosomal proteins are the most numerous nuclear non-histone proteins. HMGB domain proteins are the most abundant and well-studied HMG proteins. They are involved in variety of biological processes. HMGB1 and HMGB2 were the first members of HMGB-family to be discovered and are found in all studied eukaryotes. Despite the high degree of homology, HMGB1 and HMGB2 proteins differ from each other both in structure and functions. In contrast to HMGB2, there is a large pool of works devoted to the HMGB1 protein whose structure-function properties have been described in detail in our previous review in 2020. In this review, we attempted to bring together diverse data about the structure and functions of the HMGB2 protein. The review also describes post-translational modifications of the HMGB2 protein and its role in the development of a number of diseases. Particular attention is paid to its interaction with various targets, including DNA and protein partners. The influence of the level of HMGB2 expression on various processes associated with cell differentiation and aging and its ability to mediate the differentiation of embryonic and adult stem cells are also discussed.

Circular RNA SLTM as a miR-421-competing endogenous RNA to mediate HMGB2 expression stimulates apoptosis and inflammation in arthritic chondrocytes

Osteoarthritis (OA) is the most common age-related joint disease characterized by chronic inflammation, progressive articular cartilage destruction, and subchondral sclerosis. Accumulating evidence suggests that circular RNAs (circRNAs) play key roles in OA, but the function of circSLTM in OA remains greatly unknown. Therefore, this study focused on interleukin-1β (IL-1β)-treated primary human chondrocytes as well as a rat model to investigate the expression pattern and functional role of circSLTM in OA in vitro and in vivo. CircSLTM and high mobility group protein B2 (HMGB2) were upregulated in IL-1β-induced chondrocytes, whereas miR-421 was downregulated. Knockdown of circSLTM or overexpression of miR-421 ameliorated IL-1β-induced chondrocyte apoptosis and inflammation. The regulatory relationship between circSLTM and miR-421, as well as that between miR-421 and HMGB2, was predicted by bioinformatics and then verified by the RNA immunoprecipitation experiment and dual-luciferase reporter gene assay. Furthermore, silencing of circSLTM increased cartilage destruction and decreased cartilage tissue apoptosis rate and inflammation in a rat model of OA. Taken together, our findings demonstrate the fundamental role of circSLTM in OA progression and provide a potential molecular target for OA therapy.

Identification and characterization of high mobility group box 1 and high mobility group box 2 in Siberian sturgeon (Acipenser baerii)

High mobility group box 1 (HMGB1) and high mobility group box 2 (HMGB2) were highly conserved nonhistone chromosomal proteins involved in DNA damage repair, innate immune and inflammatory response. In this study, Acipenser baerii HMGB1 (AbHMGB1) and HMGB 2 (HMGB2) were identified. The open reading frame (ORF) of AbHMGB1 was 621 bp which encoded 206 amino acids, and the ORF of AbHMGB2 was 630 bp encoded 209 amino acids. AbHMGB1 and AbHMGB2 were conserved compared with bony fish by phylogenetic analyzing. qRT-PCR showed that AbHMGB1 and AbHMGB2 were expressed in all examined tissues, AbHMGB1 was expressed abundantly in muscle, followed by head kidney and brain, and AbHMGB2 was highest expressed in gill, followed by brain and muscle. After Streptococcus iniae infection and PAMPs treatment, AbHMGB1 and AbHMGB2 were induced significantly. This study indicated that AbHMGB1 and AbHMGB2 are involved in the process of pathogenic infection and provided a basis for exploring the mechanism of Acipenser baerii enteritis induced by Streptococcus iniae.

Damage-Associated Molecular Patterns (DAMPs) in Retinal Disorders

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules released from the extracellular and intracellular space of damaged tissue or dead cells. Recent evidence indicates that DAMPs are associated with the sterile inflammation caused by aging, increased ocular pressure, high glucose, oxidative stress, ischemia, mechanical trauma, stress, or environmental conditions, in retinal diseases. DAMPs activate the innate immune system, suggesting their role to be protective, but may promote pathological inflammation and angiogenesis in response to the chronic insult or injury. DAMPs are recognized by specialized innate immune receptors, such as receptors for advanced glycation end products (RAGE), toll-like receptors (TLRs) and the NOD-like receptor family (NLRs), and purine receptor 7 (P2X7), in systemic diseases. However, studies describing the role of DAMPs in retinal disorders are meager. Here, we extensively reviewed the role of DAMPs in retinal disorders, including endophthalmitis, uveitis, glaucoma, ocular cancer, ischemic retinopathies, diabetic retinopathy, age-related macular degeneration, rhegmatogenous retinal detachment, proliferative vitreoretinopathy, and inherited retinal disorders. Finally, we discussed DAMPs as biomarkers, therapeutic targets, and therapeutic agents for retinal disorders.