Nogo-B promotes angiogenesis and improves cardiac repair after myocardial infarction via activating Notch1 signaling

Reducing Nogo-B Improves Hepatic Fibrosis by Inhibiting BACe1-Mediated Autophagy

BACKGROUND

Hepatic fibrosis (HF) is a histopathological change in the process of long-term liver injury caused by cytokine secretion and internal environment disturbance, resulting in excessive liver repair and fiber scar. Nogo-B protein is widely distributed in peripheral tissues and organs and can regulate the migration of endothelial cells by activating TGF-β1 in vascular remodeling after injury. Nogo-B has been shown to promote organ fibrosis. This study was to determine the role of Nogo-B in HF.

METHODS

An HF model was built by intraperitoneal injections with 20% carbon tetrachloride. Localization of Nogo-B was detected by FISH. The interaction between Nogo-B and BACE1 was confirmed by Co-IP. Autophagy flux was analyzed using tandem mRFP-GFP-LC3 fluorescence microscopy, electron microscopy, and western blotting. Detection of serum AST and ALT and H&E staining were utilized to detect the degree of liver injury. The HF was evaluated by Masson trichromatic staining. RT-qPCR, western blotting, and immunofluorescence were employed to detect relevant indicators.

RESULTS

Reducing Nogo-B suppressed AST and ALT levels, the accumulation of collagen I and α-SMA, and expressions of pro-fibrotic genes in mouse liver. BACE1 was a potential downstream target of Nogo-B. Nogo-B was upregulated in TGF-β1-activated hepatic stellate cells (HSCs). Knocking down Nogo-B caused the downregulation of pro-fibrotic genes and inhibited viability of HSCs. Nogo-B knockdown prevented CCL4-induced fibrosis, accompanied by downregulation of extracellular matrix. Nogo-B inhibited HSC autophagy and increased lipid accumulation. BACE1 knockdown inhibited HSC autophagy and activation in LX-2 cells.

CONCLUSION

Nogo-B knockdown prevents HF by directly inhibiting BACe1-mediated autophagy.

Salvianic acid A sodium facilitates cardiac microvascular endothelial cell proliferation by enhancing the hypoxia-inducible factor-1 alpha/vascular endothelial growth factor signalling pathway post-myocardial infarction

Cardiac microvascular endothelial cells (CMECs) are important cells surrounding the cardiomyocytes in the heart that maintain microenvironment homeostasis. Salvianic acid A sodium (SAAS) has been reported to prevent myocardial infarction (MI) injury. However, the role of SAAS on CMEC proliferation remains unclear. CEMCs exposed to oxygen glucose deprivation (OGD) were used to explore the angiogenic abilities of SAAS. In vivo, C57BL/6 mice were divided into three groups: sham, MI and SAAS + MI groups. Compared to OGD group, SAAS led to a reduction in the apoptotic rate and an increase of the proliferation in vitro. Additionally, SAAS increased the protein levels of Bcl2, HIF-1α and vascular endothelial growth factor (VEGF) with the reduction of Bax. In terms of the specific mechanisms, SAAS might inhibit HIF-1α ubiquitination and enhance the HIF-1α/VEGF signalling pathway to increase CMEC proliferation. Furthermore, SAAS increased the density of vessels, inhibited myocardial fibrosis and improved cardiac dysfunction in vivo. The present study has revealed that SAAS could potentially be used as an active substance to facilitate CMEC proliferation post-MI.

FICD deficiency protects mice from hypertrophy-induced heart failure via BiP-mediated activation of the UPR ER and ER-phagy

Cardiomyocytes require the HSP70 chaperone BiP to maintain proteostasis in the endoplasmic reticulum (ER) following cardiac stress. The adenylyl transferase (AMPylase) FICD is increasingly recognized to regulate BiP activity through the post-translational addition of an adenosine monophosphate moiety to BiP surface residues. However, the physiological impact of FICD-mediated BiP regulation in the context of cardiovascular health is unknown. Here, we find that FICD deficiency prevents pressure overload-associated heart failure, hypertrophy, and fibrosis, and that FICD knockout mice maintain normal cardiac function after cardiac pressure overload. At a cellular level, we observe that FICD-mediated BiP AMPylation blunts the induction of the unfolded protein response (UPR ER ) and impairs BiP interaction with FAM134B, an ER-phagy receptor, thus limiting ER-phagy induction under stress. In contrast, FICD loss significantly increases BiP-dependent UPR ER induction and ER-phagy in stressed cardiomyocytes. We also uncover cell type-specific consequences of FICD activity in response to ER stress, positioning FICD as a critical proteostasis regulator in cardiac tissue. Our results highlight a novel regulatory paradigm controlling stress resilience in cardiomyocytes and offer a rationale to consider FICD as a therapeutic target to treat cardiac hypertrophy.

Oligodendrocyte Maturation Alters the Cell Death Mechanisms That Cause Demyelination

Myelinating oligodendrocytes die in human disease and early in aging. Despite this, the mechanisms that underly oligodendrocyte death are not resolved and it is also not clear whether these mechanisms change as oligodendrocyte lineage cells are undergoing differentiation and maturation. Here, we used a combination of intravital imaging, single-cell ablation, and cuprizone-mediated demyelination, in both female and male mice, to discover that oligodendrocyte maturation dictates the dynamics and mechanisms of cell death. After single-cell phototoxic damage, oligodendrocyte precursor cells underwent programmed cell death within hours, differentiating oligodendrocytes died over several days, while mature oligodendrocytes took weeks to die. Importantly cells at each maturation stage all eventually died but did so with drastically different temporal dynamics and morphological features. Consistent with this, cuprizone treatment initiated a caspase-3-dependent form of rapid cell death in differentiating oligodendrocytes, while mature oligodendrocytes never activated this executioner caspase. Instead, mature oligodendrocytes exhibited delayed cell death which was marked by DNA damage and disruption in poly-ADP-ribose subcellular localization. Thus, oligodendrocyte maturation plays a key role in determining the mechanism of death a cell undergoes in response to the same insult. This means that oligodendrocyte maturation is important to consider when designing strategies for preventing cell death and preserving myelin while also enhancing the survival of new oligodendrocytes in demyelinating conditions.

MYC acetylated lysine residues drive oncogenic cell transformation and regulate select genetic programs for cell adhesion-independent growth and survival

The MYC oncogenic transcription factor is acetylated by the p300 and GCN5 histone acetyltransferases. The significance of MYC acetylation and the functions of specific acetylated lysine (AcK) residues have remained unclear. Here, we show that the major p300-acetylated K148(149) and K157(158) sites in human (or mouse) MYC and the main GCN5-acetylated K323 residue are reversibly acetylated in various malignant and nonmalignant cells. Oncogenic overexpression of MYC enhances its acetylation and alters the regulation of site-specific acetylation by proteasome and deacetylase inhibitors. Acetylation of MYC at different K residues differentially affects its stability in a cell type-dependent manner. Lysine-to-arginine substitutions indicate that although none of the AcK residues is required for MYC stimulation of adherent cell proliferation, individual AcK sites have gene-specific functions controlling select MYC-regulated processes in cell adhesion, contact inhibition, apoptosis, and/or metabolism and are required for the malignant cell transformation activity of MYC. Each AcK site is required for anchorage-independent growth of MYC-overexpressing cells in vitro, and both the AcK148(149) and AcK157(158) residues are also important for the tumorigenic activity of MYC transformed cells in vivo. The MYC AcK site-specific signaling pathways identified may offer new avenues for selective therapeutic targeting of MYC oncogenic activities.

Cross-species conservation in the regulation of parvalbumin by perineuronal nets

Parvalbumin (PV) neurons play an integral role in regulating neural dynamics and plasticity. Therefore, understanding the factors that regulate PV expression is important for revealing modulators of brain function. While the contribution of PV neurons to neural processes has been studied in mammals, relatively little is known about PV function in non-mammalian species, and discerning similarities in the regulation of PV across species can provide insight into evolutionary conservation in the role of PV neurons. Here we investigated factors that affect the abundance of PV in PV neurons in sensory and motor circuits of songbirds and rodents. In particular, we examined the degree to which perineuronal nets (PNNs), extracellular matrices that preferentially surround PV neurons, modulate PV abundance as well as how the relationship between PV and PNN expression differs across brain areas and species and changes over development. We generally found that cortical PV neurons that are surrounded by PNNs (PV+PNN neurons) are more enriched with PV than PV neurons without PNNs (PV-PNN neurons) across both rodents and songbirds. Interestingly, the relationship between PV and PNN expression in the vocal portion of the basal ganglia of songbirds (Area X) differed from that in other areas, with PV+PNN neurons having lower PV expression compared to PV-PNN neurons. These relationships remained consistent across development in vocal motor circuits of the songbird brain. Finally, we discovered a causal contribution of PNNs to PV expression in songbirds because degradation of PNNs led to a diminution of PV expression in PV neurons. These findings in reveal a conserved relationship between PV and PNN expression in sensory and motor cortices and across songbirds and rodents and suggest that PV neurons could modulate plasticity and neural dynamics in similar ways across songbirds and rodents.

Altered Fhod3 Expression Involved in Progressive High-Frequency Hearing Loss via Dysregulation of Actin Polymerization Stoichiometry in The Cuticular Plate

Age-related hearing loss (ARHL) is a common sensory impairment with comlex underlying mechanisms. In our previous study, we performed a meta-analysis of genome-wide association studies (GWAS) in mice and identified a novel locus on chromosome 18 associated with ARHL specifically linked to a 32 kHz tone burst stimulus. Consequently, we investigated the role of Formin Homology 2 Domain Containing 3 (Fhod3), a newly discovered candidate gene for ARHL based on the GWAS results. We observed Fhod3 expression in auditory hair cells (HCs) and primarily localized at the cuticular plate (CP). To understand the functional implications of Fhod3 in the cochlea, we generated Fhod3 overexpression mice (Pax2-Cre+/-; Fhod3Tg/+) (TG) and HC-specific conditional knockout mice (Atoh1-Cre+/-; Fhod3fl/fl) (KO). Audiological assessments in TG mice demonstrated progressive high-frequency hearing loss, characterized by predominant loss of outer HCs and decrease phalloidin intensities of CP. Ultrastructural analysis revealed shortened stereocilia in the basal turn cochlea. Importantly, the hearing and HC phenotype in TG mice were replicated in KO mice. These findings indicate that Fhod3 plays a critical role in regulating actin dynamics in CP and stereocilia. Further investigation of Fhod3-related hearing impairment mechanisms may facilitate the development of therapeutic strategies for ARHL in humans.

Unveiling the modulation of Nogo receptor in neuroregeneration and plasticity: Novel aspects and future horizon in a new frontier

Neurodegenerative diseases (NDs) such as Alzheimer's, Parkinson's, Multiple Sclerosis, Hereditary Spastic Paraplegia, and Amyotrophic Lateral Sclerosis have emerged as the most dreaded diseases due to a lack of precise diagnostic tools and efficient therapies. Despite the fact that the contributing factors of NDs are still unidentified, mounting evidence indicates the possibility that genetic and cellular changes may lead to the significant production of abnormally misfolded proteins. These misfolded proteins lead to damaging effects thereby causing neurodegeneration. The association between Neurite outgrowth factor (Nogo) with neurological diseases and other peripheral diseases is coming into play. Three isoforms of Nogo have been identified Nogo-A, Nogo-B and Nogo-C. Among these, Nogo-A is mainly responsible for neurological diseases as it is localized in the CNS (Central Nervous System), whereas Nogo-B and Nogo-C are responsible for other diseases such as colitis, lung, intestinal injury, etc. Nogo-A, a membrane protein, had first been described as a CNS-specific inhibitor of axonal regeneration. Several recent studies have revealed the role of Nogo-A proteins and their receptors in modulating neurite outgrowth, branching, and precursor migration during nervous system development. It may also modulate or affect the inhibition of growth during the developmental processes of the CNS. Information about the effects of other ligands of Nogo protein on the CNS are yet to be discovered however several pieces of evidence have suggested that it may also influence the neuronal maturation of CNS and targeting Nogo-A could prove to be beneficial in several neurodegenerative diseases.

The role of rare genetic variants enrichment in epilepsies of presumed genetic etiology

Previous studies suggested that severe epilepsies e.g., developmental and epileptic encephalopathies (DEE) are mainly caused by ultra-rare de novo genetic variants. For milder phenotypes, rare genetic variants could contribute to the phenotype. To determine the importance of rare variants for different epilepsy types, we analyzed a whole-exome sequencing cohort of 9,170 epilepsy-affected individuals and 8,436 controls. Here, we separately analyzed three different groups of epilepsies : severe DEEs, genetic generalized epilepsy (GGE), and non-acquired focal epilepsy (NAFE). We required qualifying rare variants (QRVs) to occur in controls at a minor allele frequency ≤ 1:1,000, to be predicted as deleterious (CADD≥20), and to have an odds ratio in epilepsy cases ≥2. We identified genes enriched with QRVs in DEE (n=21), NAFE (n=72), and GGE (n=32) - the number of enriched genes are found greatest in NAFE and least in DEE. This suggests that rare variants may play a more important role for causality of NAFE than in DEE. Moreover, we found that QRV-carrying genes e.g., HSGP2, FLNA or TNC are involved in structuring the brain extracellular matrix. The present study confirms an involvement of rare variants for NAFE, while in DEE and GGE, the contribution of such variants appears more limited.

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 trended upwards at 7 days and significantly increased at 14 days post- ligation. Macrophages, which participate in extracellular matrix remodeling, Gli1 + and PDGFRα + stromal cells, which may deposit extracellular matrix, both increased with injury. Using single-cell RNA-sequencing, we found that a majority of Gli1 + cells at embryonic day 16 also express Pdgfra and/or Pdgfrb. However, in adult mice, only a small subset of Gli1 + cells express PDGFRα and/or PDGFRβ at the protein level. Using 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. Pdgfra + /Pdgfrb + stromal cell subpopulations both expanded in response to ligation, showed increased expression and a greater diversity of matrisome genes expressed, consistent with these cells being fibrogenic. Defining the signaling pathways driving fibrotic responses in stromal cell sub-types could reveal future therapeutic targets.

S-Propargyl-Cysteine Ameliorates Peripheral Nerve Injury through Microvascular Reconstruction

Microvascular reconstruction is essential for peripheral nerve repair. S-Propargyl-cysteine (SPRC), the endogenous hydrogen sulfide (H₂S) donor, has been reported to promote angiogenesis. The aim of this study is to utilize the pro-angiogenic ability of SPRC to support peripheral nerve repair and to explore the potential mechanisms. The effects and mechanisms of SPRC on angiogenesis and peripheral nerve repair were examined under hypoxic condition by establishing a sciatic nerve crushed injury model in mice and rats, and a hypoxia model in human umbilical vascular endothelial cells (HUVECs) in vitro. We found that SPRC accelerated the function recovery of the injured sciatic nerve and alleviated atrophy of the gastrocnemius muscle in mice. It facilitated the viability of Schwann cells (SCs), the outgrowth and myelination of regenerated axons, and angiogenesis in rats. It enhanced the viability, proliferation, adhesion, migration, and tube formation of HUVECs under hypoxic condition. SPRC activated sirtuin1 (SIRT1) expression by promoting the production of endogenous H₂S, and SIRT1 negatively regulated Notch signaling in endothelial cells (ECs), thereby promoting angiogenesis. Collectively, our study has provided important evidence that SPRC has an effective role in peripheral nerve repair through microvascular reconstruction, which could be a potentially effective medical therapy for peripheral nerve injury.

The nanoscale organization of reticulon 4 shapes local endoplasmic reticulum structure in situ

The endoplasmic reticulum’s (ER) structure is directly linked to the many functions of the ER but its formation is not fully understood. We investigate how the ER-membrane curving protein reticulon 4 (Rtn4) localizes to and organizes in the membrane and how that affects local ER structure. We show a strong correlation between the local Rtn4 density and the local ER membrane curvature. Our data further reveal that the typical ER tubule possesses an elliptical cross-section with Rtn4 enriched at either end of the major axis. Rtn4 oligomers are linear-shaped, contain about five copies of the protein, and preferentially orient parallel to the tubule axis. Our observations support a mechanism in which oligomerization leads to an increase of the local Rtn4 concentration with each molecule increasing membrane curvature through a hairpin wedging mechanism. This quantitative analysis of Rtn4 and its effects on the ER membrane result in a new model of tubule shape as it relates to Rtn4.

SUMMARY

Rtn4 forms linear-shaped oligomers that contain an average of five Rtn4 proteins, localize to the sides of elliptical tubules, prefer orientations near parallel to the tubule axis, and increase local curvature of the ER membrane by increasing local Rtn4 density.

Danhong injection combined with tPA protects the BBB through Notch-VEGF signaling pathway on long-term outcomes of thrombolytic therapy

Current therapy for ischemic stroke primarily relies on tissue plasminogen activator (tPA), but it is limited by narrow treatment time window, bleeding complications and neurotoxicity. The preliminary study of tPA plus Danhong injection (DHI) shows that it can significantly reduce the side effects of tPA and improve its thrombolytic effect, but the mechanism of this action has not been further studied. In this study, the rats were randomly divided into sham group, vehicle group, DHI group (4 mL/kg), tPA group (5 mg/kg) and DHI+tPA group (4 mL/kg+ 2.5 mg/kg), administered intravenously 4.5 h since focal embolic stroke modeling. After 3 days and 7 days of cerebral ischemia, the neurological function of each treatment group was significantly improved compared with the vehicle group. The combination of DHI and tPA significantly reduced Evans blue (EB) penetration as well as the expressions of the proteins MMP-9, PAI-1 and P-selectin, while upregulating the expressions of claudin-5, occludin, and ZO-1 mRNA. Furthermore, the effect of continuous 7-day treatment was more conspicuous than 3-day treatment. Then, it significantly reduced the expressions of the proteins DLL-4 and VEGFR-2, increased the expressions of Notch-1, HIF-1α and HES-1 mRNA, and promoted the expressions of VEGF/HIF-1α-positive cells at 14 days following stroke. Hematoxylin-eosin (HE) staining and transmission electron microscopy (TEM) also showed that it improved pathological changes of ischemic brain tissue and the cerebral cortex micro-structure. These indicate that DHI combined with tPA may significantly ameliorate blood-brain barrier (BBB) disruption by activating Notch-VEGF signaling pathway to promote angiogenesis for long-term outcomes.