The serine protease inhibitor TLCK attenuates intrinsic death pathways in neurons upstream of mitochondrial demise

Opportunities and Perspectives for Three Dimensional Culture of Mesenchymal Stem Cell-Derived Exosomes

Exosomes are nanosized extracellular vesicles (EVs) that participate in intercellular communication through surface proteins and the delivery of internal cargo. The exosomes have gained attention for their potential as disease biomarkers and therapeutic agents. The therapeutic ability of exosomes has been verified by copious previous studies. Effective methods for extensive clinical applications are being researched for exosome-based regenerative therapies, including the application of 3D cultures to enhance exosome production and secretion, which can resolve limited exosome secretion from the parent cells. Cell culture has emerged as a crucial approach for biomedical research because of its many benefits. Both well-established continuous cell lines and primary cell cultures continue to be invaluable for basic research and clinical application. Previous studies have shown that three-dimensional cultured exosomes (3D-Exo) improve therapeutic properties and yields compared with traditional culture systems. Since the majority of studies have focused on exosomes derived from mesenchymal stem cells (MSC-Exo), this review will also concentrate on MSC-Exo. In this review, we will summarize the advantages of 3D-Exo and introduce the 3D culture system and methods of exosome isolation, providing scientific strategies for the diagnosis, treatment, and prognosis of a wide variety of diseases.

Three-Dimensional-Cultured MSC-Derived Exosome-Hydrogel Hybrid Microneedle Array Patch for Spinal Cord Repair

Exosomes derived from mesenchymal stem cells (MSCs) have been proven to exhibit great potentials in spinal cord injury (SCI) therapy. However, conventional two-dimensional (2D) culture will inevitably lead to the loss of stemness of MSCs, which substantially limits the therapeutic potency of MSCs exosomes (2D-Exo). Exosomes derived from three-dimensional culture (3D-Exo) possess higher therapeutic efficiency which have wide applications in spinal cord therapy. Typically, conventional exosome therapy that relies on local repeated injection results in secondary injury and low efficiency. It is urgent to develop a more reliable, convenient, and effective exosome delivery method to achieve constant in situ exosomes release. Herein, we proposed a controlled 3D-exohydrogel hybrid microneedle array patch to achieve SCI repair in situ. Our studies suggested that MSCs with 3D-culturing could maintain their stemness, and consequently, 3D-Exo effectively reduced SCI-induced inflammation and glial scarring. Thus, it is a promising therapeutic strategy for the treatment of SCI.

Mechanism of Ferroptosis and Its Relationships With Other Types of Programmed Cell Death: Insights for Potential Interventions After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a fatal cerebrovascular disease with high morbidity and mortality, for which no effective therapies are currently available. Brain tissue damage caused by ICH is mediated by a newly identified form of non-apoptotic programmed cell death, called ferroptosis. Ferroptosis is characterized by the iron-induced accumulation of lipid reactive oxygen species (ROS), leading to intracellular oxidative stress. Lipid ROS cause damage to nucleic acids, proteins, and cell membranes, eventually resulting in ferroptosis. Numerous biological processes are involved in ferroptosis, including iron metabolism, lipid peroxidation, and glutathione biosynthesis; therefore, iron chelators, lipophilic antioxidants, and other specific inhibitors can suppress ferroptosis, suggesting that these modulators are beneficial for treating brain injury due to ICH. Accumulating evidence indicates that ferroptosis differs from other types of programmed cell death, such as necroptosis, apoptosis, oxytosis, and pyroptosis, in terms of ultrastructural characteristics, signaling pathways, and outcomes. Although several studies have emphasized the importance of ferroptosis due to ICH, the detailed mechanism underlying ferroptosis remains unclear. This review summarizes the available evidence on the mechanism underlying ferroptosis and its relationship with other types of cell death, with the aim to identify therapeutic targets and potential interventions for ICH.

The Inter-α-Trypsin Inhibitor Family: Versatile Molecules in Biology and Pathology

Inter-α-trypsin inhibitor (IαI) family members are ancient and unique molecules that have evolved over several hundred million years of vertebrate evolution. IαI is a complex containing the proteoglycan bikunin to which heavy chain proteins are covalently attached to the chondroitin sulfate chain. Besides its matrix protective activity through protease inhibitory action, IαI family members interact with extracellular matrix molecules and most notably hyaluronan, inhibit complement, and provide cell regulatory functions. Recent evidence for the diverse roles of the IαI family in both biology and pathology is reviewed and gives insight into their pivotal roles in tissue homeostasis. In addition, the clinical uses of these molecules are explored, such as in the treatment of inflammatory conditions including sepsis and Kawasaki disease, which has recently been associated with severe acute respiratory syndrome coronavirus 2 infection in children.

Mitochondrial damage by α-synuclein causes cell death in human dopaminergic neurons

Evolving concepts on Parkinson’s disease (PD) pathology suggest that α-synuclein (aSYN) promote dopaminergic neuron dysfunction and death through accumulating in the mitochondria. However, the consequence of mitochondrial aSYN localisation on mitochondrial structure and bioenergetic functions in neuronal cells are poorly understood. Therefore, we investigated deleterious effects of mitochondria-targeted aSYN in differentiated human dopaminergic neurons in comparison with wild-type (WT) aSYN overexpression and corresponding EGFP (enhanced green fluorescent protein)-expressing controls. Mitochondria-targeted aSYN enhanced mitochondrial reactive oxygen species (ROS) formation, reduced ATP levels and showed severely disrupted structure and function of the dendritic neural network, preceding neuronal death. Transmission electron microscopy illustrated distorted cristae and many fragmented mitochondria in response to WT-aSYN overexpression, and a complete loss of cristae structure and massively swollen mitochondria in neurons expressing mitochondria-targeted aSYN. Further, the analysis of mitochondrial bioenergetics in differentiated dopaminergic neurons, expressing WT or mitochondria-targeted aSYN, elicited a pronounced impairment of mitochondrial respiration. In a pharmacological compound screening, we found that the pan-caspase inhibitors QVD and zVAD-FMK, and a specific caspase-1 inhibitor significantly prevented aSYN-induced cell death. In addition, the caspase inhibitor QVD preserved mitochondrial function and neuronal network activity in the human dopaminergic neurons overexpressing aSYN. Overall, our findings indicated therapeutic effects by caspase-1 inhibition despite aSYN-mediated alterations in mitochondrial morphology and function.

The role of thrombin in the pathogenesis of diabetic neuropathy

Diabetic neuropathy is common and disabling despite glycemic control. Novel neuroprotective approaches are needed. Thrombin and hypercoagulability are associated with diabetes and nerve conduction dysfunction. Our aim was to study the role of thrombin in diabetic neuropathy. We measured thrombin activity by a biochemical assay in streptozotocin (STZ)-induced diabetic neuropathy in male Sprague-Dawley rats. Neuropathy severity was assessed by thermal latency and nerve conduction measures. Thermal latencies were longer in diabetic rats, and improved with the non-specific serine-protease inhibitor Tosyl-L-lysine-chloromethyl ketone (TLCK) treatment (p<0.01). The tail nerve of diabetic rats showed slow conduction velocity (p˂0.01), and interestingly, increased thrombin activity was noted in the sciatic nerve (p˂0.001). Sciatic nodes of Ranvier and the thrombin receptor, protease activated receptor 1 (PAR1) reactivity showed abnormal morphology in diabetic animals by immunofluorescence staining (p<0.0001). Treatment of diabetic animals with either the specific thrombin inhibitor, N-alpha 2 naphtalenesulfonylglycyl alpha-4 amidino-phenylalaninepiperidide (NAPAP) or TLCK preserved normal conduction velocity, (p˂0.01 and p = 0.01 respectively), and prevented disruption of morphology (p˂0.05 and p˂0.03). The results establish for the first time an association between diabetic neuropathy and excessive activation of the thrombin pathway. Treatment of diabetic animals with thrombin inhibitors ameliorates both biochemical, structural and electrophysiological deficits. The thrombin pathway inhibition may be a novel neuroprotective therapeutic target in the diabetic neuropathy pathology.

Metabolic switch induced by Cimicifuga racemosa extract prevents mitochondrial damage and oxidative cell death

BACKGROUND

Cimicifuga racemosa extract is a well-established therapy for menopausal symptoms. The mechanisms underlying the multiple therapeutic effects of Cimicifuga extract, e.g. reducing hot flushes and profuse sweating are not well defined. Recent studies revealed pronounced effects of Ze 450, a Cimicifuga racemosa extract that was produced by a standardized procedure, on energy metabolism through activation of AMP-activated protein kinase in vitro and beneficial anti-diabetic effects in vivo.

PURPOSE

The aim of the study was to investigate the effects of Ze 450 on energy metabolism. Since mitochondria are the key regulators of cellular energy homeostasis, we wanted to elucidate whether Ze 450 affects mitochondrial resilience and can provide protection against oxidative damage in neuronal and liver cells.

METHODS/STUDY DESIGN

In this study, we investigated the effects of Ze 450 (1-200 µg/ml) on mitochondrial integrity and function, and cell viability in models of oxidative stress induced by erastin and RSL-3 in neuronal and liver cells. The effects of Ze 450 in control conditions and after induction of oxidative stress were analyzed using FACS for detecting lipid peroxidation (BODIPY), mitochondrial ROS formation (MitoSOX), mitochondrial membrane potential (TMRE) and cell death (AnnexinV/PI staining). Furthermore, we determined metabolic activity (MTT assay), ATP levels and mitochondrial respiration and glycolysis (oxygen consumption rates, extracellular acidification rates; Seahorse).

RESULTS

Ze 450 preserved mitochondrial integrity and ATP levels, and prevented mitochondrial ROS formation, loss of mitochondrial membrane potential and cell death. Notably, Cimicifuga racemosa extract alone did not alter mitochondrial ROS levels, and subtle inhibitory effects on cell proliferation were reversed after withdrawal of the extract. In addition, Ze 450 did not exert toxic effects to liver cells, but rather protected these from the oxidative challenge. Further analysis of the mitochondrial oxygen consumption rate and the extracellular acidification rate revealed that Ze 450 mediated a switch from mitochondrial respiration to glycolysis, and this metabolic shift was a prerequisite for the protective effects against oxidative damage.

CONCLUSION

In conclusion, the bioenergetic shift induced by Ze 450 exerted protective effects in different cell types, and offers promising therapeutic potential in age related diseases involving oxidative stress and mitochondrial damage.

Inhibition of HIF-prolyl-4-hydroxylases prevents mitochondrial impairment and cell death in a model of neuronal oxytosis

Mitochondrial impairment induced by oxidative stress is a main characteristic of intrinsic cell death pathways in neurons underlying the pathology of neurodegenerative diseases. Therefore, protection of mitochondrial integrity and function is emerging as a promising strategy to prevent neuronal damage. Here, we show that pharmacological inhibition of hypoxia-inducible factor prolyl-4-hydroxylases (HIF-PHDs) by adaptaquin inhibits lipid peroxidation and fully maintains mitochondrial function as indicated by restored mitochondrial membrane potential and ATP production, reduced formation of mitochondrial reactive oxygen species (ROS) and preserved mitochondrial respiration, thereby protecting neuronal HT-22 cells in a model of glutamate-induced oxytosis. Selective reduction of PHD1 protein using CRISPR/Cas9 technology also reduced both lipid peroxidation and mitochondrial impairment, and attenuated glutamate toxicity in the HT-22 cells. Regulation of activating transcription factor 4 (ATF4) expression levels and related target genes may mediate these beneficial effects. Overall, these results expose HIF-PHDs as promising targets to protect mitochondria and, thereby, neurons from oxidative cell death.

Expression and localization of Inter-alpha Inhibitors in rodent brain

Inter-alpha Inhibitor Proteins (IAIPs) are a family of related serine protease inhibitors. IAIPs are important components of the systemic innate immune system. We have identified endogenous IAIPs in the central nervous system (CNS) of sheep during development and shown that treatment with IAIPs reduces neuronal cell death and improves behavioral outcomes in neonatal rats after hypoxic-ischemic brain injury. The presence of IAIPs in CNS along with their exogenous neuroprotective properties suggests that endogenous IAIPs could be part of the innate immune system in CNS. The purpose of this study was to characterize expression and localization of IAIPs in CNS. We examined cellular expressions of IAIPs in vitro in cultured cortical mouse neurons, in cultured rat neurons, microglia, and astrocytes, and in vivo on brain sections by immunohistochemistry from embryonic (E) day 18 mice and postnatal (P) day 10 rats. Cultured cortical mouse neurons expressed the light chain gene Ambp and heavy chain genes Itih-1, 2, 3, 4, and 5 mRNA transcripts and IAIP proteins. IAIP proteins were detected by immunohistochemistry in cultured cells as well as brain sections from E18 mice and P10 rats. Immunoreactivity was found in neurons, microglia, astrocytes and oligodendroglia in multiple brain regions including cortex and hippocampus, as well as within both the ependyma and choroid plexus. Our findings suggest that IAIPs are endogenous proteins expressed in a wide variety of cell types and regions both in vitro and in vivo in rodent CNS. We speculate that endogenous IAIPs may represent endogenous neuroprotective immunomodulatory proteins within the CNS.

Ferroptosis: Death by Lipid Peroxidation

Ferroptosis is a regulated form of cell death driven by loss of activity of the lipid repair enzyme glutathione peroxidase 4 (GPX4) and subsequent accumulation of lipid-based reactive oxygen species (ROS), particularly lipid hydroperoxides. This form of iron-dependent cell death is genetically, biochemically, and morphologically distinct from other cell death modalities, including apoptosis, unregulated necrosis, and necroptosis. Ferroptosis is regulated by specific pathways and is involved in diverse biological contexts. Here we summarize the discovery of ferroptosis, the mechanism of ferroptosis regulation, and its increasingly appreciated relevance to both normal and pathological physiology.