Extracellular vesicles activate ATM-Chk2 signaling pathway through the intercellular transfer of mitochondrial DNA in HBV-infected human hepatocytes

A new strategy for drug delivery systems in oral diseases using stem cell-derived extracellular vesicles: review and new perspectives

Extracellular vesicles (EVs) are membrane vesicles derived from cells and serve as an endogenous mechanism for intercellular communication. Since the discovery of their capacity to effectively transfer biological information, their potential as drug delivery vehicles has garnered significant scientific interest. Particularly, EVs derived from mesenchymal cells (MSC-EVs) have emerged as a highly promising method for drug delivery. They can transport bioactive molecules, such as nucleic acids, lipids, and proteins, and possess the ability to modulate immune responses, transmit information, and target specific cells. EVs offer several advantages over conventional drug delivery systems, including their capacity to traverse natural barriers, inherent cell targeting capabilities, and stability in circulation. Compared to their parent cells, EVs exhibit low immunogenicity, ease of storage and transport, and a reduced risk of tumorigenesis. The diagnosis and treatment of oral diseases often involve invasive measures, and MSC-EVs have demonstrated initial efficacy in oral disease treatment. This review explores the application of MSC-EVs in maxillofacial tissue regeneration, periodontitis, temporomandibular joint osteoarthritis, Sjögren's Syndrome, oral cancer, and other oral diseases. Additionally, it outlines potential future directions for the development of MSC-EVs. This review aims to provide a comprehensive understanding of MSC-EVs in oral disease treatment and to stimulate interest in their applications for targeted drug delivery.

Mitochondrial Extracellular Vesicles: A Promising Avenue for Diagnosing and Treating Lung Diseases

Mitochondria, pivotal organelles governing cellular biosynthesis, energy metabolism, and signal transduction, maintain dynamic equilibrium through processes such as biogenesis, fusion, fission, and mitophagy. Growing evidence implicates mitochondrial dysfunction in a spectrum of respiratory diseases including acute lung injury/acute respiratory distress syndrome, bronchial asthma, pulmonary fibrosis, chronic obstructive pulmonary disease, and lung cancer. Consequently, identifying methods capable of ameliorating damaged mitochondrial function is crucial for the treatment of pulmonary diseases. Extracellular vesicles (EVs), nanosized membrane vesicles released by cells into the extracellular space, facilitate intercellular communication by transferring bioactive substances or signals between cells or organs. Recent studies have identified abundant mitochondrial components within specific subsets of EVs, termed mitochondrial extracellular vesicles (mitoEVs), whose contents and compositions vary with disease progression. Moreover, mitoEVs have demonstrated reparative mitochondrial functions in injured recipient cells. However, a comprehensive understanding of mitoEVs is currently lacking, limiting their clinical translation prospects. This Review explores the biogenesis, classification, functional mitochondrial cargo, and biological effects of mitoEVs, with a focus on their role in pulmonary diseases. Emphasis is placed on their potential as biological markers and innovative therapeutic strategies in pulmonary diseases, offering fresh insights for mechanistic studies and drug development in various pulmonary disorders.

Release of damaged mitochondrial DNA: A novel factor in stimulating inflammatory response

Mitochondrial DNA (mtDNA) is a circular double-stranded genome that exists independently of the nucleus. In recent years, research on mtDNA has significantly increased, leading to a gradual increase in understanding of its physiological and pathological characteristics. Reactive oxygen species (ROS) and other factors can damage mtDNA. This damaged mtDNA can escape from the mitochondria to the cytoplasm or extracellular space, subsequently activating immune signaling pathways, such as NLR family pyrin domain protein 3 (NLRP3), and triggering inflammatory responses. Numerous studies have demonstrated the involvement of mtDNA damage and leakage in the pathological mechanisms underlying various diseases including infectious diseases, metabolic inflammation, and immune disorders. Consequently, comprehensive investigation of mtDNA can elucidate the pathological mechanisms underlying numerous diseases. The prevention of mtDNA damage and leakage has emerged as a novel approach to disease treatment, and mtDNA has emerged as a promising target for drug development. This article provides a comprehensive review of the mechanisms underlying mtDNA-induced inflammation, its association with various diseases, and the methods used for its detection.

Hepatitis C virus NS5B triggers an MDA5-mediated innate immune response by producing dsRNA without the replication of viral genomes

During the replication of viral genomes, RNA viruses produce double-stranded RNA (dsRNA), through the activity of their RNA-dependent RNA polymerases (RdRps) as viral replication intermediates. Recognition of viral dsRNA by host pattern recognition receptors - such as retinoic acid-induced gene-I (RIG-I)-like receptors and Toll-like receptor 3 - triggers the production of interferon (IFN)-β via the activation of IFN regulatory factor (IRF)-3. It has been proposed that, during the replication of viral genomes, each of RIG-I and melanoma differentiation-associated gene 5 (MDA5) form homodimers for the efficient activation of a downstream signalling pathway in host cells. We previously reported that, in the non-neoplastic human hepatocyte line PH5CH8, the RdRp NS5B derived from hepatitis C virus (HCV) could induce IFN-β expression by its RdRp activity without the actual replication of viral genomes. However, the exact mechanism by which HCV NS5B produced IFN-β remained unknown. In the present study, we first showed that NS5B derived from another Flaviviridae family member, GB virus B (GBV-B), also possessed the ability to induce IFN-β in PH5CH8 cells. Similarly, HCV NS5B, but not its G317V mutant, which lacks RdRp activity, induced the dimerization of MDA5 and subsequently the activation of IRF-3. Interestingly, immunofluorescence analysis showed that HCV NS5B produced dsRNA. Like HCV NS5B, GBV-B NS5B also triggered the production of dsRNA and subsequently the dimerization of MDA5. Taken together, our results show that HCV NS5B triggers an MDA5-mediated innate immune response by producing dsRNA without the replication of viral genomes in human hepatocytes.

Mitochondria-derived vesicles and their potential roles in kidney stone disease

Recent evidence has shown significant roles of mitochondria-derived vesicles (MDVs) in mitochondrial quality control (MQC) system. Under mild stress condition, MDVs are formed to carry the malfunctioned mitochondrial components, such as mitochondrial DNA (mtDNA), peptides, proteins and lipids, to be eliminated to restore normal mitochondrial structure and functions. Under severe oxidative stress condition, mitochondrial dynamics (fission/fusion) and mitophagy are predominantly activated to rescue mitochondrial structure and functions. Additionally, MDVs generation can be also triggered as the major MQC machinery to cope with unhealthy mitochondria when mitophagy is unsuccessful for eliminating the damaged mitochondria or mitochondrial fission/fusion fail to recover the mitochondrial structure and functions. This review summarizes the current knowledge on MDVs and discuss their roles in physiologic and pathophysiologic conditions. In addition, the potential clinical relevance of MDVs in therapeutics and diagnostics of kidney stone disease (KSD) are emphasized.

Many Ways to Communicate-Crosstalk between the HBV-Infected Cell and Its Environment

Chronic infection with the hepatitis B virus (HBV) affects an estimated 257 million people worldwide and can lead to liver diseases such as cirrhosis and liver cancer. Viral replication is generally considered not to be cytopathic, and although some HBV proteins may have direct carcinogenic effects, the majority of HBV infection-related disease is related to chronic inflammation resulting from disrupted antiviral responses and aberrant innate immune reactions. Like all cells, healthy and HBV-infected cells communicate with each other, as well as with other cell types, such as innate and adaptive immune cells. They do so by both interacting directly and by secreting factors into their environment. Such factors may be small molecules, such as metabolites, single viral proteins or host proteins, but can also be more complex, such as virions, protein complexes, and extracellular vesicles. The latter are small, membrane-enclosed vesicles that are exchanged between cells, and have recently gained a lot of attention for their potential to mediate complex communication and their potential for therapeutic repurposing. Here, we review how HBV infection affects the communication between HBV-infected cells and cells in their environment. We discuss the impact of these interactions on viral persistence in chronic infection, as well as their relation to HBV infection-related pathology.

Tetramethylpyrazine prevents liver fibrotic injury in mice by targeting hepatocyte-derived and mitochondrial DNA-enriched extracellular vesicles

Liver fibrosis is the common consequence of almost all liver diseases and has become an urgent clinical problem without efficient therapies. Recent evidence has shown that hepatocytes-derived extracellular vesicles (EVs) play important roles in liver pathophysiology, but little is known about the role of damaged hepatocytes-derived EVs in hepatic stellate cell (HSC) activation and following fibrosis. Tetramethylpyrazine (TMP) from Ligusticum wallichii Franchat exhibits a broad spectrum of biological activities including liver protection. In this study, we investigated whether TMP exerted liver-protective action through regulating EV-dependent intercellular communication between hepatocytes and HSCs. Chronic liver injury was induced in mice by CCl₄ (1.6 mg/kg, i.g.) twice a week for 8 weeks. In the last 4 weeks of CCl₄ administration, mice were given TMP (40, 80, 160 mg·kg^-1·d^-1, i.g.). Acute liver injury was induced in mice by injection of a single dose of CCl₄ (0.8 mg/kg, i.p.). After injection, mice were treated with TMP (80 mg/kg) every 24 h. We showed that TMP treatment dramatically ameliorated CCl₄-induced oxidative stress and hepatic inflammation as well as acute or chronic liver fibrosis. In cultured mouse primary hepatocytes (MPHs), treatment with CCl₄ or acetaminophen resulted in mitochondrial dysfunction, release of mitochondrial DNA (mtDNA) from injured hepatocytes to adjacent hepatocytes and HSCs through EVs, mediating hepatocyte damage and fibrogenic responses in activated HSCs; pretreatment of MPHs with TMP (25 μM) prevented all these pathological effects. Transplanted serum EVs from TMP-treated mice prevented both initiation and progression of liver fibrosis caused by CCl₄. Taken together, this study unravels the complex mechanisms underlying the protective effects of TMP against mtDNA-containing EV-mediated hepatocyte injury and HSC activation during liver injury, and provides critical evidence inspiring the development of TMP-based innovative therapeutic agents for the treatment of liver fibrosis.

ATM-Dependent Phosphorylation of Hepatitis B Core Protein in Response to Genotoxic Stress

Chronic hepatitis caused by infection with the Hepatitis B virus is a life-threatening condition. In fact, 1 million people die annually due to liver cirrhosis or hepatocellular carcinoma. Recently, several studies demonstrated a molecular connection between the host DNA damage response (DDR) pathway and HBV replication and reactivation. Here, we investigated the role of Ataxia-telangiectasia-mutated (ATM) and Ataxia telangiectasia and Rad3-related (ATR) PI3-kinases in phosphorylation of the HBV core protein (HBc). We determined that treatment of HBc-expressing hepatocytes with genotoxic agents, e.g., etoposide or hydrogen peroxide, activated the host ATM-Chk2 pathway, as determined by increased phosphorylation of ATM at Ser1981 and Chk2 at Thr68. The activation of ATM led, in turn, to increased phosphorylation of cytoplasmic HBc at serine-glutamine (SQ) motifs located in its C-terminal domain. Conversely, down-regulation of ATM using ATM-specific siRNAs or inhibitor effectively reduced etoposide-induced HBc phosphorylation. Detailed mutation analysis of S-to-A HBc mutants revealed that S170 (S168 in a 183-aa HBc variant) is the primary site targeted by ATM-regulated phosphorylation. Interestingly, mutation of two major phosphorylation sites involving serines at positions 157 and 164 (S155 and S162 in a 183-aa HBc variant) resulted in decreased etoposide-induced phosphorylation, suggesting that the priming phosphorylation at these serine-proline (SP) sites is vital for efficient phosphorylation of SQ motifs. Notably, the mutation of S172 (S170 in a 183-aa HBc variant) had the opposite effect and resulted in massively up-regulated phosphorylation of HBc, particularly at S170. Etoposide treatment of HBV infected HepG2-NTCP cells led to increased levels of secreted HBe antigen and intracellular HBc protein. Together, our studies identified HBc as a substrate for ATM-mediated phosphorylation and mapped the phosphorylation sites. The increased expression of HBc and HBe antigens in response to genotoxic stress supports the idea that the ATM pathway may provide growth advantage to the replicating virus.