High-mobility group box 1 protein antagonizes the immunosuppressive capacity and therapeutic effect of mesenchymal stem cells in acute kidney injury

Activation of the HMGB1-TLR4 pathway impacts the functionality of bone marrow mesenchymal stem cells and disrupts macrophage polarization in immune thrombocytopenia

Recent evidence suggests that immune thrombocytopenia (ITP), a common bleeding disorder, is linked to an imbalance in macrophage polarization and impaired bone marrow mesenchymal stem cells (BMSCs). However, the relationship between macrophage polarization imbalance and functional defects in BMSCs, as well as the involvement of associated molecules in BMSCs' defects, is not well understood. This study aimed to investigate the regulatory effects of high mobility group protein 1 (HMGB1) on the physiological functions of BMSCs, specifically in relation to macrophage polarization imbalance. Patients with ITP showed dysregulation in monocyte/macrophage polarization and impaired BMSCs function. HMGB1 was found to have a negative impact on the ability of BMSCs to regulate the imbalance in macrophage polarization, especially when inflammatory factors are present. The MyD88-dependent pathway downstream of BMSCs was found to be significantly enhanced with HMGB1 treatment. Furthermore, treatment with toll-like receptor 4 (TLR4) inhibitors successfully restored the regulatory capacity of BMSCs in ameliorating macrophage polarization imbalance and effectively inhibited the activation of the MyD88-dependent pathway. Meanwhile, infusion of si-TLR4-BMSCs reversed HMGB1-induced platelet dysfunction and reduced over-polarization to M1-like macrophages in the ITP mouse model. Consequently, targeting the HMGB1-TLR4 pathway could be a potential approach to restore the immunoregulatory function of BMSCs.

Azilsartan Modulates HMGB1/NF-κB/p38/ERK1/2/JNK and Apoptosis Pathways during Renal Ischemia Reperfusion Injury

Renal ischemia/reperfusion (IR) injury is characterized by an unexpected impairment of blood flow to the kidney. Azilsartan is an angiotensin receptor blocker that is approved for the management of hypertension. The present study aimed to investigate, on molecular basics, the nephroprotective activity of azilsartan on renal IR injury in rats. Rats were assigned into four groups: (1) Sham group, (2) Azilsartan group, (3) IR group, and (4) IR/Azilsartan-treated group. Histological examination and renal function were evaluated. Levels of KIM-1, HMGB1, caspase 3, GPX, SOD, NF-κB, and p53 proteins were investigated using ELISA. mRNA levels of IL-1β, IL6, IL10, TNF-α, NF-κB, p53, and bax were assessed by qRT-PCR. Expression of p38, JNK, and ERK1/2 proteins was investigated by Western blotting. IR injury resulted in tissue damage, elevation of creatinine, BUN, KIM-1, HMGB1, caspase 3, NF-κB, and p53 levels, decreasing GPX and SOD activities, and up-regulation of NF-κB, IL-1β, IL6, TNF-α, p53, and bax genes. Furthermore, it up-regulated the expression of phosphorylated/total ratio of p38, ERK1/2, and JNK proteins. Interestingly, treatment of the injured rats with azilsartan significantly alleviated IR injury-induced histopathological and biochemical changes. It reduced the creatinine, BUN, KIM-1, HMGB1, caspase-3, NF-κB, and p53 levels, elevated GPX and SOD activities, down-regulated the expression of NF-κB, IL-1β, IL6, TNF-α, p53, and bax genes, and up-regulated IL10 gene expression. Furthermore, it decreased the phosphorylated/total ratio of p38, ERK1/2, and JNK proteins. Azilsartan exhibited nephroprotective activity in IR-injured rats via its antioxidant effect, suppression of inflammation, attenuation of apoptosis, and inhibition of HMGB1/NF-κB/p38/ERK1/2/JNK signaling pathway.

miR-22 alleviates sepsis-induced acute kidney injury via targeting the HMGB1/TLR4/NF-κB signaling pathway

BACKGROUND

Acute kidney injury (AKI) is a severe complication of sepsis, and is strongly correlated with MicroRNAs (miRNAs). However, the mechanism of miR-22 on sepsis-induced AKI is not clearly understood. The study aimed to explore the role and mechanism of miR-22 on AKI.

METHODS

The AKI models were established by cecal ligation and puncture (CLP) surgery in SD rats and lipopolysaccharide (LPS) induction in HBZY-1 cells. In AKI rats, the content of serum creatinine (SCr) and blood urea nitrogen (BUN) were detected. Kidney tissues were pathologically examined by H&E and PAS staining. The LPS-induced HBZY-1 cells were transfected with mimics miR-22, si-HMGB1, or oe-HMGB1. miR-22 and HMGB1 expression was detected in vivo and in vitro. In transfected cells, HMGB1/TLR4/NF-κB pathway-related protein expressions were measured by Western blot. The relationship between miR-22 and HMGB1 was assessed by a dual-luciferase gene report. Inflammatory cytokine levels in serum and cells were assessed by ELISA.

RESULTS

In AKI rats, kidney injury was observed, accompanied by the down-regulated miR-122 expression and up-regulated HMBG1 expression. The dual-luciferase report found miR-22-3p could targetly regulate HMBG1. Furthermore, both in vitro and in vivo experiments revealed that the releases of inflammatory cytokine were increased after AKI modeling, but the situation was reversed by mimics miR-22 or si-HMGB1 in vitro. In HBZY-1 cells, mimics miR-22 could suppress LPS-induced overexpression of HMGB1/TLR4/NF-κB signaling pathway-related proteins. However, the oe-HMGB1 addition reversed the effect of mimics miR-22.

CONCLUSION

miR-22 can inhibit the inflammatory response, target the HMGB1, and inhibit the HMGB1/TLR4/NF-kB pathway, to attenuate the sepsis-induced AKI, which indicates that miR-22 may serve as a potential treatment target in sepsis-induced AKI.

LPS preconditioning of MSC-CM improves protection against hypoxia/reoxygenation-induced damage in H9c2 cells partly via HMGB1/Bach1 signalling

Mesenchymal stem cell-derived conditioned medium (MSC-CM) improves cardiac function after myocardial infarction; however, this cardioprotective effect is moderate and transient. Lipopolysaccharide (LPS) pretreatment partially improves MSC-CM-mediated cardioprotective effects owing to the presence of paracrine factors. However, the mechanism underlying these improved effects remains unknown. To study the effect of LPS-pretreated MSC-CM on hypoxia/reoxygenation (H/R)-induced injury, MSCs were treated with or without LPS (400 ng/mL) for 48 h, and the supernatant was collected (MSC-CM). Subsequently, H9c2 cells were co-cultured with Nor-CM (CM derived from LPS-untreated MSCs) and LPS-CM (CM derived from LPS-pretreated MSCs) for 24 h and subjected to H/R. MSC-CM inhibited the progression of H/R-induced injury in H9c2 cells, and this protective effect was enhanced via LPS pretreatment as evidenced by the improved apoptosis assessment index (i.e. caspase-3 and B-cell lymphoma-2 [Bcl-2] expression) and decreased levels of lactic dehydrogenase (LDH) and cardiac troponin (cTn). In addition, the results of haematoxylin-eosin staining (H&E), transmission electron microscopy (TEM) and TdT-mediated dUTP nick-end labelling (TUNEL) validated that MSC-CM inhibited H/R-induced injury in H9c2 cardiomyocytes. LPS pretreatment downregulated the expression of high mobility group box-1 (HMGB1) and BTB and CNC homology-1 (Bach1) proteins in MSCs but upregulated the expression of vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF) and insulin-like growth factor (IGF). HMGB1 knockdown (MSC/siHMGB1-CM) significantly decreased the expression of Bach1 and increased the expression of VEGF, HGF and IGF. Bach1 knockdown (MSC/siBach1-CM) did not alter the production of HMGB1 but increased the expression of VEGF and IGF. LPS pretreatment did not alter the expression of the paracrine factors VEGF and HGF in the MSC/siHMGB1 group but increased their expression in the MSC/siBach1 group. The myocyte anti-apoptotic effects of MSCs/siBach1-CM were similar to those of untreated MSCs, which were not enhanced by LPS. LPS-pretreated MSC-CM protects H9c2 cells against H/R-induced injury partly through the HMGB1/Bach1 signalling pathway.

The mechanism of HMGB1 secretion and release

High mobility group box 1 (HMGB1) is a nonhistone nuclear protein that has multiple functions according to its subcellular location. In the nucleus, HMGB1 is a DNA chaperone that maintains the structure and function of chromosomes. In the cytoplasm, HMGB1 can promote autophagy by binding to BECN1 protein. After its active secretion or passive release, extracellular HMGB1 usually acts as a damage-associated molecular pattern (DAMP) molecule, regulating inflammation and immune responses through different receptors or direct uptake. The secretion and release of HMGB1 is fine-tuned by a variety of factors, including its posttranslational modification (e.g., acetylation, ADP-ribosylation, phosphorylation, and methylation) and the molecular machinery of cell death (e.g., apoptosis, pyroptosis, necroptosis, alkaliptosis, and ferroptosis). In this minireview, we introduce the basic structure and function of HMGB1 and focus on the regulatory mechanism of HMGB1 secretion and release. Understanding these topics may help us develop new HMGB1-targeted drugs for various conditions, especially inflammatory diseases and tissue damage.

A nuclear protein that gets released after cell death or is actively secreted by immune cells offers a promising therapeutic target for treating diseases linked to excessive inflammation. Daolin Tang from the University of Texas Southwestern Medical Center in Dallas, USA, and colleagues review how cellular stresses can trigger the accumulation of HMGB1, a type of alarm signal protein that promotes the recruitment and activation of inflammation-promoting immune cells. The researchers discuss various mechanisms that drive both passive and active release of HMGB1 into the space around cells. These processes, which include enzymatic modifications of the HMGB1 protein, cell–cell interactions and molecular pathways of cell death, could be targeted by drugs to lessen tissue damage and inflammatory disease caused by HMGB1-induced immune responses

Human embryonic stem cell-derived melanocytes exhibit limited immunogenicity

Although surgical interventions have become optional for refractory vitiligo, grafting related injuries is inevitable. Embryonic stem cell (ESC) derivatives can be used in transplantation to address this issue, but the immune rejection due to allogeneic transplantation is of great concern. To investigate the immunogenicity of ESC derived melanocytes (ES-MC), we established a co-culture system of ES-MC and allogeneic PBMC. The results showed that ES-MC were similar to human primary melanocytes, with low expression of immune related molecules, and limited capability of stimulating allogeneic lymphocytes in vitro. Taken together, our findings confirm that ES-MC are of limited immunogenicity, providing new insights into the application of ES-MC in the regenerative medicine such as treating vitiligo.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: A Potential Therapeutic Strategy for Acute Kidney Injury

Acute kidney injury (AKI) is a common and potential life-threatening disease in patients admitted to hospital, affecting 10%-15% of all hospitalizations and around 50% of patients in the intensive care unit. Severe, recurrent, and uncontrolled AKI may progress to chronic kidney disease or end-stage renal disease. AKI thus requires more efficient, specific therapies, rather than just supportive therapy. Mesenchymal stem cells (MSCs) are considered to be promising cells for cellular therapy because of their ease of harvesting, low immunogenicity, and ability to expand in vitro. Recent research indicated that the main therapeutic effects of MSCs were mediated by MSC-derived extracellular vesicles (MSC-EVs). Furthermore, compared with MSCs, MSC-EVs have lower immunogenicity, easier storage, no tumorigenesis, and the potential to be artificially modified. We reviewed the therapeutic mechanism of MSCs and MSC-EVs in AKI, and considered recent research on how to improve the efficacy of MSC-EVs in AKI. We also summarized and analyzed the potential and limitations of EVs for the treatment of AKI to provide ideas for future clinical trials and the clinical application of MSC-EVs in AKI.

HMGB1, the Next Predictor of Transcatheter Arterial Chemoembolization for Liver Metastasis of Colorectal Cancer?

HMGB1 is an important mediator of inflammation during ischemia-reperfusion injury on organs. The serum expression of HMGB1 was increased significantly on the 1st day after TACE and decreased significantly which was lower on the 30th day after TACE. Tumor markers of post-DEB-TACE decreased significantly. The correlational analysis showed that patients with low HMGB1 expression had lower risks of fever and liver injury compared those with the higher expression, while the ORR is relatively worse. Patients with lower expression of HMGB1 had longer PFS, better efficacy, and higher quality of life. With the high post-expression, the low expression had lower incidence of fever and liver injury too. There was no statistical difference in the one-year survival among the different groups. The quality of life of all patients was improved significantly. The over-expression of HMGB1 in LMCRC is an adverse prognostic feature and a positive predictor of response to TACE.