Anti-fibrotic mechanism of SPP1 knockdown in atrial fibrosis associates with inhibited mitochondrial DNA damage and TGF-β/SREBP2/PCSK9 signaling

A longitudinal molecular and cellular lung atlas of lethal SARS-CoV-2 infection in K18-hACE2 transgenic mice

BACKGROUND

The global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to approximately 500 million cases and 6 million deaths worldwide. Previous investigations into the pathophysiology of SARS-CoV-2 primarily focused on peripheral blood mononuclear cells from patients, lacking detailed mechanistic insights into the virus's impact on inflamed tissue. Existing animal models, such as hamster and ferret, do not faithfully replicate the severe SARS-CoV-2 infection seen in patients, underscoring the need for more relevant animal system-based research.

METHODS

In this study, we employed single-cell RNA sequencing (scRNA-seq) with lung tissues from K18-hACE2 transgenic (TG) mice during SARS-CoV-2 infection. This approach allowed for a comprehensive examination of the molecular and cellular responses to the virus in lung tissue.

FINDINGS

Upon SARS-CoV-2 infection, K18-hACE2 TG mice exhibited severe lung pathologies, including acute pneumonia, alveolar collapse, and immune cell infiltration. Through scRNA-seq, we identified 36 different types of cells dynamically orchestrating SARS-CoV-2-induced pathologies. Notably, SPP1+ macrophages in the myeloid compartment emerged as key drivers of severe lung inflammation and fibrosis in K18-hACE2 TG mice. Dynamic receptor-ligand interactions, involving various cell types such as immunological and bronchial cells, defined an enhanced TGFβ signaling pathway linked to delayed tissue regeneration, severe lung injury, and fibrotic processes.

INTERPRETATION

Our study provides a comprehensive understanding of SARS-CoV-2 pathogenesis in lung tissue, surpassing previous limitations in investigating inflamed tissues. The identified SPP1+ macrophages and the dysregulated TGFβ signaling pathway offer potential targets for therapeutic intervention. Insights from this research may contribute to the development of innovative diagnostics and therapies for COVID-19.

FUNDING

This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2020M3A9I2109027, 2021R1A2C2004501).

The Role of Biochemical Cardiac Markers in Atrial Fibrillation

Atrial fibrillation (AF) is the most common type of cardiac arrhythmia. Proteins are a component of cardiac biomarkers containing cell structures that are released into the circulation when a myocardial injury occurs. They are essential in the diagnosis, risk assessment, and treatment of patients who have chest pain, are thought to have acute coronary syndrome, or are experiencing acute heart failure exacerbations. There are numerous biochemical cardiac markers, but this article summarizes the basic role of major biochemical cardiac markers, including cardiac natriuretic peptides, cardiac troponins, C-reactive protein (CRP), creatine kinase-MB, heart-type fatty acid-binding protein, ischemia-modified albumin, lipoprotein (a), osteopontin (OPN), and soluble suppression of tumorigenicity 2 (sST2), in AF. Atrial natriuretic peptide may serve as an indicator of atrial integrity, which may help to select appropriate treatment approaches for AF. Higher levels of N-terminal pro-B-type natriuretic peptide and brain natriuretic peptide are predictive of incidental AF. Increased troponin T release may indicate better clinical results following AF ablation. Similarly, CRP increases the risk of the AF-increasing calcium (Ca) influx in atrial myocytes, but not because of atrial fibrosis. Patients with postoperative AF have lower FABP3 gene expression in the atrium. Lipoprotein (a) (Lp[a]) may play a causative role in the onset of AF and impact various cardiac tissues. Clinical trials for Lp(a)-lowering drugs should assess their impact on preventing AF. Also, OPN was highly expressed in the circulation of AF patients and further increased with the progression of AF. sST2 was a reliable predictor of new-onset AF and can improve the accuracy of the AF risk model. There is a greater chance that these cardiac biomarkers might be employed to enhance clinical risk stratification in AF.

Identifying fibrogenic cells following salivary gland obstructive injury

Fibrosis results from excess extracellular matrix accumulation, which alters normal tissue architecture and impedes function. In the salivary gland, fibrosis can be induced by irradiation treatment for cancer therapy, Sjögren's Disease, and other causes; however, it is unclear which stromal cells and signals participate in injury responses and disease progression. As hedgehog signaling has been implicated in fibrosis of the salivary gland and other organs, we examined contributions of the hedgehog effector, Gli1, to fibrotic responses in salivary glands. To experimentally induce a fibrotic response in female murine submandibular salivary glands, we performed ductal ligation surgery. We detected a progressive fibrotic response where both extracellular matrix accumulation and actively remodeled collagen significantly increased at 14 days post-ligation. Macrophages, which participate in extracellular matrix remodeling, and Gli1+ and PDGFRα+ stromal cells, which may deposit extracellular matrix, both increased with injury. Using single-cell RNA-sequencing, Gli1 + cells were not found in discrete clusters at embryonic day 16 but were found in clusters expressing the stromal genes Pdgfra and/or Pdgfrb. In adult mice, Gli1+ cells were similarly heterogeneous but more cells co-expressed PDGFRα and PDGFRβ. Using Gli1-CreERT2; ROSA26tdTomato lineage-tracing mice, we found that Gli1-derived cells expand with ductal ligation injury. Although some of the Gli1 lineage-traced tdTomato+ cells expressed vimentin and PDGFRβ following injury, there was no increase in the classic myofibroblast marker, smooth muscle alpha-actin. Additionally, there was little change in extracellular matrix area, remodeled collagen area, PDGFRα, PDGFRβ, endothelial cells, neurons, or macrophages in Gli1 null salivary glands following injury when compared with controls, suggesting that Gli1 signaling and Gli1+ cells have only a minor contribution to mechanical injury-induced fibrotic changes in the salivary gland. We used scRNA-seq to examine cell populations that expand with ligation and/or showed increased expression of matrisome genes. Some Pdgfra + /Pdgfrb + stromal cell subpopulations expanded in response to ligation, with two stromal cell subpopulations showing increased expression of Col1a1 and a greater diversity of matrisome genes, consistent with these cells being fibrogenic. However, only a few cells in these subpopulations expressed Gli1, consistent with a minor contribution of these cells to extracellular matrix production. Defining the signaling pathways driving fibrotic responses in stromal cell sub-types could reveal future therapeutic targets.

Novel Thioether-Bridged 2,6-Disubstituted and 2,5,6-Trisubstituted Imidazothiadiazole Analogues: Synthesis, Antiproliferative Activity, ADME, and Molecular Docking Studies

In this study, starting from 2-amino-1,3,4-thiadiazole derivatives (3-5), a new series of 2,6-disubstituted (compounds 7-15) and 2,5,6-trisubstituted (compounds 16-33) imidazo[2,1-b][1,3,4]-thiadiazole derivatives were synthesized using cyclization and Mannich reaction mechanisms, respectively. All synthesized compounds were characterized by ¹ H-NMR, ¹³ C-NMR, FT-IR, elemental analysis, and mass spectroscopy techniques. Also, X-ray diffraction analysis were used for compounds 4, 7, 11, 17, and 19. The cytotoxic effects of the new compounds on the viability of colon cancer cells (DLD-1), lung cancer cells (A549), and liver cancer cells (HepG2) were investigated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method in vitro. Compound 15 was found to be the most potent anticancer drug candidate in this series with an IC₅₀ value of 3.63 μM against HepG2 for 48 h. Moreover, the absorption, distribution, metabolism, and excretion (ADME) parameters of the synthesized compounds were calculated and thus, their potential to be safe drugs was evaluated. Finally, to support the biological activity experiments, molecular docking studies of these compounds were carried out on three different target cancer protein structures (PDB IDs: 5ETY, 1M17, and 3GCW), and the amino acids that play key roles in the binding of the compounds to these proteins were determined.

Downregulation of amphiregulin improves cardiac hypertrophy via attenuating oxidative stress and apoptosis

Amphiregulin (AREG) is a ligand of epidermal growth factor receptor and participates in the fibrosis of multiple organs. However, whether AREG can regulate hypertrophic cardiomyopathy is not well known. This research aims to explore the effect of AREG on cardiac hypertrophy, and whether the oxidative stress and apoptosis was involved in the influence of AREG on cardiac hypertrophy. Angiotensin (Ang) II induced cardiac hypertrophy in mice and neonatal rat cardiomyocytes (NRCMs) or HL-1 cells in vitro. AREG expressions raised in the heart of mice. After AREG downregulation, the increases of Ang II induced cardiac weight and cardiomyocytes area were inhibited. Down-regulation of AREG could inhibit Ang II induced the increases of atrial natriuretic peptide, brain natriuretic peptide, beta-myosin heavy chain in the heart of mice, and NRCMs and HL-1 cells. The enhancement of oxidative stress in mice heart with Ang II treatment was alleviated by AREG knockdown. The raises of Ang II induced Bax and cleaved caspase3 in mice heart were inhibited by AREG downregulation. AREG downregulation reduced myocardial hypertrophy via inhibition of oxidative and apoptosis. AREG may be a target for future cardiac hypertrophy treatment.

Clinical and Molecular Implications of Osteopontin in Heart Failure

The matricellular protein osteopontin modulates cell-matrix interactions during tissue injury and healing. A complex multidomain structure of osteopontin enables it not only to bind diverse cell receptors but also to interact with various partners, including other extracellular matrix proteins, cytokines, and growth factors. Numerous studies have implicated osteopontin in the development and progression of myocardial remodeling in diverse cardiac diseases. Osteopontin influences myocardial remodeling by regulating extracellular matrix production, the activity of matrix metalloproteinases and various growth factors, inflammatory cell recruitment, myofibroblast differentiation, cardiomyocyte apoptosis, and myocardial vascularization. The exploitation of osteopontin loss- and gain-of-function approaches in rodent models provided an opportunity for assessment of the cell- and disease-specific contribution of osteopontin to myocardial remodeling. In this review, we summarize the recent knowledge on osteopontin regulation and its impact on various cardiac diseases, as well as delineate complex disease- and cell-specific roles of osteopontin in cardiac pathologies. We also discuss the current progress of therapeutics targeting osteopontin that may facilitate the development of a novel strategy for heart failure treatment.