Pramlintide regulation of extracellular matrix (ECM) and apoptosis through mitochondrial-dependent pathways in human nucleus pulposus cells

Roles of organokines in intervertebral disc homeostasis and degeneration

The intervertebral disc is not isolated from other tissues. Recently, abundant research has linked intervertebral disc homeostasis and degeneration to various systemic diseases, including obesity, metabolic syndrome, and diabetes. Organokines are a group of diverse factors named for the tissue of origin, including adipokines, osteokines, myokines, cardiokines, gastrointestinal hormones, and hepatokines. Through endocrine, paracrine, and autocrine mechanisms, organokines modulate energy homeostasis, oxidative stress, and metabolic balance in various tissues to mediate cross-organ communication. These molecules are involved in the regulation of cellular behavior, inflammation, and matrix metabolism under physiological and pathological conditions. In this review, we aimed to summarize the impact of organokines on disc homeostasis and degeneration and the underlying signaling mechanism. We focused on the regulatory mechanisms of organokines to provide a basis for the development of early diagnostic and therapeutic strategies for disc degeneration.

The role of endoplasmic reticulum stress, mitochondrial dysfunction and their crosstalk in intervertebral disc degeneration

Low back pain (LBP) is a pervasive global health issue. Roughly 40% of LBP cases are attributed to intervertebral disc degeneration (IVDD). While the underlying mechanisms of IVDD remain incompletely understood, it has been confirmed that apoptosis and extracellular matrix (ECM) degradation caused by many factors such as inflammation, oxidative stress, calcium (Ca2+) homeostasis imbalance leads to IVDD. Endoplasmic reticulum (ER) stress and mitochondrial dysfunction are involved in these processes. The initiation of ER stress precipitates cell apoptosis, and is also related to inflammation, levels of oxidative stress, and Ca2+ homeostasis. Additionally, mitochondrial dynamics, antioxidative systems, disruption of Ca2+ homeostasis are closely associated with Reactive Oxygen Species (ROS) and inflammation, promoting cell apoptosis. However, numerous crosstalk exists between the ER and mitochondria, where they interact through inflammatory cytokines, signaling pathways, ROS, or key molecules such as CHOP, forming positive and negative feedback loops. Furthermore, the contact sites between the ER and mitochondria, known as mitochondria-associated membranes (MAM), facilitate direct signal transduction such as Ca2+ transfer. However, the current attention towards this issue is insufficient. Therefore, this review summarizes the impacts of ER stress and mitochondrial dysfunction on IVDD, along with the possibly potential crosstalk between them, aiming to unveil novel avenues for IVDD intervention.

PLAGL2 induces nucleus pulposus cell apoptosis via regulating RASSF5 expression and thus accelerates intervertebral disc degeneration

Excessive apoptosis of nucleus pulposus (NP) cells is the main pathological change in intervertebral disc degeneration (IVDD) progression. Pleomorphic adenoma gene like-2 (PLAGL2) plays a key role in cell apoptosis, however, the effect of PLAGL2 on IVDD has not been clarified yet. In this study, we established mouse IVDD models via the annulus fibrosis needle puncture, TUNEL and safranin O staining were used to verify the successful establishment of IVDD models, and PLAGL2 expression was detected in disc tissues. Then, NP cells isolated from disc tissues were used to construct PLAGL2 knockdown cells. PLAGL2 expression in NP cells was analyzed with qRT-PCR and Western blot. The impact of PLAGL2 on the viability, apoptosis, and mitochondria function of NP cells was evaluated by MTT assay, TUNEL, JC1 staining, and flow cytometry assay. Additionally, the regulatory mechanism of PLAGL2 was further assessed. We found that PLAGL2 was upregulated in IVDD disc tissues and serum deprivation (SD)-stimulated NP cells. PLAGL2 knockdown inhibited apoptosis and mitochondria damage in NP cells. Moreover, knockdown of PLAGL2 downregulated the expression of downstream apoptosis-related factors RASSF5, Nip3, and p73. Mechanically, PLAGL2 transcriptionally activated RASSF5 via binding to its promoter. In general, our findings indicate that PLAGL2 induces apoptosis in NP cells and aggravates IVDD progression. This study provides a promising therapeutic target for IVDD treatment.

Intracellular and microenvironmental regulation of mitochondrial membrane potential in cancer cells

Cancer cells have an abnormally high mitochondrial membrane potential (ΔΨm ), which is associated with enhanced invasive properties in vitro and increased metastases in vivo. The mechanisms underlying the abnormal ΔΨm in cancer cells remain unclear. Research on different cell types has shown that ΔΨm is regulated by various intracellular mechanisms such as by mitochondrial inner and outer membrane ion transporters, cytoskeletal elements, and biochemical signaling pathways. On the other hand, the role of extrinsic, tumor microenvironment (TME) derived cues in regulating ΔΨm is not well defined. In this review, we first summarize the existing literature on intercellular mechanisms of ΔΨm regulation, with a focus on cancer cells. We then offer our perspective on the different ways through which the microenvironmental cues such as hypoxia and mechanical stresses may regulate cancer cell ΔΨm . This article is categorized under: Cancer > Environmental Factors Cancer > Biomedical Engineering Cancer > Molecular and Cellular Physiology.

Pramlintide: An Amylin Analogue Protects Endothelial Cells against Oxidative Stress through Regulating Oxidative Markers and NF-κb Expression

Background:

Oxidative stress has a prominent role in the pathogenesis of diabetes complications. Pramlintide is an injectional amylin analogue used for the treatment of type 1 and type 2 diabetic patients. The present investigation evaluated the effect of pramlintide against oxidative damage induced by hydrogen peroxide (H₂O₂) in human umbilical vein endothelial cells (HUVECs).

Methods:

Cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Hydroperoxides level, ferric reducing antioxidant power (FRAP), and expression of transcription factor NF-κB were measured in HUVECs that pretreated with pramlintide and, then exposed to H₂O₂.

Results:

Pramlintide significantly decreased the cytotoxicity caused by H₂O₂ at the concentrations of 5 and 10 μg/mL. Pretreatment of HUVECs with pramlintide reduced hydroperoxides and increased FRAP value in intra- and extra-cellular mediums at different concentration ranges compared with H₂O₂ stimulated cells. Pramlintide (10 μg/mL) remarkably ameliorated the expression of NF-κB gene after 1, 3 and 24 h exposure to H₂O₂.

Conclusions:

Findings of the current investigation displayed that pramlintide may act as a protective against oxidative conditions in endothelial cells through modulation of oxidative markers and transcription factor NF-κB.

AMPK as a Potential Therapeutic Target for Intervertebral Disc Degeneration

As the principal reason for low back pain, intervertebral disc degeneration (IDD) affects the health of people around the world regardless of race or region. Degenerative discs display a series of characteristic pathological changes, including cell apoptosis, senescence, remodeling of extracellular matrix, oxidative stress and inflammatory local microenvironment. As a serine/threonine-protein kinase in eukaryocytes, AMP-activated protein kinase (AMPK) is involved in various cellular processes through the modulation of cell metabolism and energy balance. Recent studies have shown the abnormal activity of AMPK in degenerative disc cells. Besides, AMPK regulates multiple crucial biological behaviors in IDD. In this review, we summarize the pathophysiologic changes of IDD and activation process of AMPK. We also attempt to generalize the role of AMPK in the pathogenesis of IDD. Moreover, therapies targeting AMPK in alleviating IDD are analyzed, for better insight into the potential of AMPK as a therapeutic target.

Steatosis induced by nonylphenol in HepG2 cells and the intervention effect of curcumin

Non-alcoholic fatty liver disease (NAFLD) has increasingly become a serious public health problem. There is growing evidence that nonylphenol (NP) exposure may cause steatosis, but the underlying mechanism is not fully understood. Curcumin (CUR) improves NAFLD-related lipid metabolism disorders and oxidative stress, but its preventive and therapeutic effects on NP-induced steatosis have not been reported. The objective of this investigation was to determine the capability and potential mechanism of NP to induce steatosis in vitro and the intervention of curcumin. HepG2 cells were treated with 0 μM, 20 μM, 30 μM, 40 μM NP for 24 h. Lipid droplets accumulated significantly in HepG2 cells after NP treatment, and the concentration of triglyceride (TG) and total cholesterol (T-CHO) increased significantly. Simultaneously, lipogenesis gene expression was up-regulated significantly, fatty acid oxidation (FAO) gene expression was significantly down-regulated, and reactive oxygen species (ROS) were overproduced. Meanwhile, the expression of p-AMPK/AMPK in the AMPK/mTOR signaling pathway was significantly down-regulated and the expression of p-mTOR/mTOR was markedly up-regulated. However, blocking ROS production with N-acetyl-L-cysteine (NAC) can reverse these phenomena. In addition, our study found that curcumin effectively ameliorated the effects of NP-induced steatosis. Our study indicates that NP can induce steatosis in HepG2 cells, and may be implicated in inhibiting the ROS-dependent AMPK/mTOR pathway, and that curcumin ameliorates the NAFLD-like changes induced by NP in HepG2 cells.

Targeting mitochondrial dysfunction with small molecules in intervertebral disc aging and degeneration

The prevalence of rheumatic and musculoskeletal diseases (RMDs) including osteoarthritis (OA) and low back pain (LBP) in aging societies present significant cost burdens to health and social care systems. Intervertebral disc (IVD) degeneration, which is characterized by disc dehydration, anatomical alterations, and extensive changes in extracellular matrix (ECM) composition, is an important contributor to LBP. IVD cell homeostasis can be disrupted by mitochondrial dysfunction. Mitochondria are the main source of energy supply in IVD cells and a major contributor to the production of reactive oxygen species (ROS). Therefore, mitochondria represent a double-edged sword in IVD cells. Mitochondrial dysfunction results in oxidative stress, cell death, and premature cell senescence, which are all implicated in IVD degeneration. Considering the importance of optimal mitochondrial function for the preservation of IVD cell homeostasis, extensive studies have been done in recent years to evaluate the efficacy of small molecules targeting mitochondrial dysfunction. In this article, we review the pathogenesis of mitochondrial dysfunction, aiming to highlight the role of small molecules and a selected number of biological growth factors that regulate mitochondrial function and maintain IVD cell homeostasis. Furthermore, molecules that target mitochondria and their mechanisms of action and potential for IVD regeneration are identified. Finally, we discuss mitophagy as a key mediator of many cellular events and the small molecules regulating its function.

Targeted therapy for intervertebral disc degeneration: inhibiting apoptosis is a promising treatment strategy

Intervertebral disc (IVD) degeneration (IDD) is a multifactorial pathological process associated with low back pain (LBP). The pathogenesis is complicated, and the main pathological changes are IVD cell apoptosis and extracellular matrix (ECM) degradation. Apoptotic cell loss leads to ECM degradation, which plays an essential role in IDD pathogenesis. Apoptosis regulation may be a potential attractive therapeutic strategy for IDD. Previous studies have shown that IVD cell apoptosis is mainly induced by the death receptor pathway, mitochondrial pathway, and endoplasmic reticulum stress (ERS) pathway. This article mainly summarizes the factors that induce IDD and apoptosis, the relationship between the three apoptotic pathways and IDD, and potential therapeutic strategies. Preliminary animal and cell experiments show that targeting apoptotic pathway genes or drug inhibition can effectively inhibit IVD cell apoptosis and slow IDD progression. Targeted apoptotic pathway inhibition may be an effective strategy to alleviate IDD at the gene level. This manuscript provides new insights and ideas for IDD therapy.

Neuroprotective Effects of the Amylin Analog, Pramlintide, on Alzheimer's Disease Are Associated with Oxidative Stress Regulation Mechanisms

Administration of the recombinant analog of the pancreatic amyloid amylin, Pramlintide, has shown therapeutic benefits in aging and Alzheimer's disease (AD) models, both on cognition and amyloid-β (Aβ) pathology. However, the neuroprotective mechanisms underlying the benefits of Pramlintide remain unclear. Given the early and critical role of oxidative stress in AD pathogenesis and the known reactive oxygen species (ROS) modulating function of amyloids, we sought to determine whether Pramlintide's neuroprotective effects involve regulation of oxidative stress mechanisms. To address this, we treated APP/PS1 transgenic mice with Pramlintide for 3 months, starting at 5.5 months prior to widespread AD pathology onset, and measured cognition (Morris Water Maze), AD pathology, and oxidative stress-related markers and enzymes in vivo. In vitro, we determined the ability of Pramlintide to modulate H2O2-induced oxidative stress levels. Our data show that Pramlintide improved cognitive function, altered amyloid-processing enzymes, reduced plaque burden in the hippocampus, and regulated endogenous antioxidant enzymes (MnSOD and GPx1) and the stress marker HO-1 in a location specific manner. In vitro, Pramlintide treatment in neuronal models reduced H2O2-induced endogenous ROS production and lipid peroxidation in a dose-dependent manner. Together, these results indicate that Pramlintide's benefits on cognitive function and pathology may involve antioxidant-like properties of this compound.

The effect of pramlintide, an antidiabetic amylin analogue, on angiogenesis-related markers in vitro

Background and purpose:

Irregularities of angiogenesis may participate in the pathogenesis of diabetes complications. Pramlintide is an amylin analogue administered for the treatment of type 1 and type 2 diabetes. The present investigation aimed at surveying the effect of pramlintide on angiogenesis-related markers in human umbilical vein endothelial cells (HUVECs).

Experimental approach:

The proliferation of cells was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) method. The effect of pramlintide on migration was estimated by Transwell® assay. in vitro evaluation of angiogenesis was performed by tube formation assay. The secretion of vascular endothelial growth factor (VEGF) to the supernatant of HUVECs was measured by an enzyme- linked immunosorbent assay (ELISA) kit. All experiments were performed in triplicate.

Findings / Results:

Pramlintide exhibited no inhibitory effect on HUVECs proliferation. It significantly increased cell migration at the concentration of 1 μg/mL. Pramlintide (1 μg/mL) also enhanced average tubules length, size, and the mean number of junctions. However, there was not any significant change in VEGF release from HUVECs.

Conclusion and implications:

Findings of this research revealed the effect of pramlintide on angiogenesis- related markers via enhancing migration and tubulogenesis in vitro, suggesting a worthwhile proposition for further clinical researches on improving vascular complications and healing of diabetic wounds.