An ERK5-NRF2 Axis Mediates Senescence-Associated Stemness and Atherosclerosis.

BACKGROUND: ERK5 (extracellular signal-regulated kinase 5) is a dual kinase transcription factor containing an N-terminal kinase domain and a C-terminal transcriptional activation domain. Many ERK5 kinase inhibitors have been developed and tested to treat cancer and inflammatory diseases. However, recent data have raised questions about the role of the catalytic activity of ERK5 in proliferation and inflammation. We aimed to investigate how ERK5 reprograms myeloid cells to the proinflammatory senescent phenotype, subsequently leading to atherosclerosis. METHODS: A ERK5 S496A (dephosphorylation mimic) knock in (KI) mouse model was generated using CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated 9), and atherosclerosis was characterized by hypercholesterolemia induction. The plaque phenotyping in homozygous ERK5 S496A KI and wild type (WT) mice was studied using imaging mass cytometry. Bone marrow-derived macrophages were isolated from hypercholesterolemic mice and characterized using RNA sequencing and functional in vitro approaches, including senescence, mitochondria reactive oxygen species, and inflammation assays, as well as by metabolic extracellular flux analysis. RESULTS: We show that atherosclerosis was inhibited in ERK5 S496A KI mice. Furthermore, ERK5 S496 phosphorylation mediates both senescence-associated secretory phenotype and senescence-associated stemness by upregulating AHR (aryl hydrocarbon receptor) in plaque and bone marrow-derived macrophages isolated from hypercholesterolemic mice. We also discovered that ERK5 S496 phosphorylation could induce NRF2 (NFE2-related factor 2) SUMOylation at a novel K518 site to inhibit NRF2 transcriptional activity without altering ERK5 catalytic activity and mediates oxidized LDL (low-density lipoprotein)-induced senescence-associated secretory phenotype. Specific ERK5 kinase inhibitors (AX15836 and XMD8-92) also inhibited ERK5 S496 phosphorylation, suggesting the involvement of ERK5 S496 phosphorylation in the anti-inflammatory effects of these ERK5 kinase inhibitors. CONCLUSIONS: We discovered a novel mechanism by which the macrophage ERK5-NRF2 axis develops a unique senescence-associated secretory phenotype/stemness phenotype by upregulating AHR to engender atherogenesis. The finding of senescence-associated stemness phenotype provides a molecular explanation to resolve the paradox of senescence in proliferative plaque by permitting myeloid cells to escape the senescence-induced cell cycle arrest during atherosclerosis formation.

Polymer-Functionalized Mitochondrial Transplantation to Fibroblasts Counteracts a Pro-Fibrotic Phenotype.

Fibroblast-to-myofibroblast transition (FMT) leads to excessive extracellular matrix (ECM) deposition-a well-known hallmark of fibrotic disease. Transforming growth factor-ß (TGF-ß) is the primary cytokine driving FMT, and this phenotypic conversion is associated with mitochondrial dysfunction, notably a metabolic reprogramming towards enhanced glycolysis. The objective of this study was to examine whether the establishment of favorable metabolic phenotypes in TGF-ß-stimulated fibroblasts could attenuate FMT. The hypothesis was that mitochondrial replenishment of TGF-ß-stimulated fibroblasts would counteract a shift towards glycolytic metabolism, consequently offsetting pro-fibrotic processes. Isolated mitochondria, functionalized with a dextran and triphenylphosphonium (TPP) (Dex-TPP) polymer conjugate, were administered to fibroblasts (MRC-5 cells) stimulated with TGF-ß, and effects on bioenergetics and fibrotic programming were subsequently examined. Results demonstrate that TGF-ß stimulation of fibroblasts led to FMT, which was associated with enhanced glycolysis. Dex-TPP-coated mitochondria (Dex-TPP/Mt) delivery to TGF-ß-stimulated fibroblasts abrogated a metabolic shift towards glycolysis and led to a reduction in reactive oxygen species (ROS) generation. Importantly, TGF-ß-stimulated fibroblasts treated with Dex-TPP/Mt had lessened expression of FMT markers and ECM proteins, as well as reduced migration and proliferation. Findings highlight the potential of mitochondrial transfer, as well as other strategies involving functional reinforcement of mitochondria, as viable therapeutic modalities in fibrosis.

The Role of Calcium Signaling in Melanoma.

Calcium signaling plays important roles in physiological and pathological conditions, including cutaneous melanoma, the most lethal type of skin cancer. Intracellular calcium concentration ([Ca2+]i), cell membrane calcium channels, calcium related proteins (S100 family, E-cadherin, and calpain), and Wnt/Ca2+ pathways are related to melanogenesis and melanoma tumorigenesis and progression. Calcium signaling influences the melanoma microenvironment, including immune cells, extracellular matrix (ECM), the vascular network, and chemical and physical surroundings. Other ionic channels, such as sodium and potassium channels, are engaged in calcium-mediated pathways in melanoma. Calcium signaling serves as a promising pharmacological target in melanoma treatment, and its dysregulation might serve as a marker for melanoma prediction. We documented calcium-dependent endoplasmic reticulum (ER) stress and mitochondria dysfunction, by targeting calcium channels and influencing [Ca2+]i and calcium homeostasis, and attenuated drug resistance in melanoma management.

Enhanced Succinate Oxidation with Mitochondrial Complex II Reactive Oxygen Species Generation in Human Prostate Cancer.

The transformation of prostatic epithelial cells to prostate cancer (PCa) has been characterized as a transition from citrate secretion to citrate oxidation, from which one would anticipate enhanced mitochondrial complex I (CI) respiratory flux. Molecular mechanisms for this transformation are attributed to declining mitochondrial zinc concentrations. The unique metabolic properties of PCa cells have become a hot research area. Several publications have provided indirect evidence based on investigations using pre-clinical models, established cell lines, and fixed or frozen tissue bank samples. However, confirmatory respiratory analysis on fresh human tissue has been hampered by multiple difficulties. Thus, few mitochondrial respiratory assessments of freshly procured human PCa tissue have been published on this question. Our objective is to document relative mitochondrial CI and complex II (CII) convergent electron flow to the Q-junction and to identify electron transport system (ETS) alterations in fresh PCa tissue. The results document a CII succinate: quinone oxidoreductase (SQR) dominant succinate oxidative flux model in the fresh non-malignant prostate tissue, which is enhanced in malignant tissue. CI NADH: ubiquinone oxidoreductase activity is impaired rather than predominant in high-grade malignant fresh prostate tissue. Given these novel findings, succinate and CII are promising targets for treating and preventing PCa.

EpCAM-Targeting Aptamer Radiotracer for Tumor-Specific PET Imaging.

Noninvasive in vivo imaging to measure the expression of EpCAM, a biomarker overexpressed in the majority of carcinoma tumors and metastatic lesions, is highly desirable for accurate tumor staging and therapy evaluation. Here, we report the use of an aptamer radiotracer to enable tumor-specific EpCAM-targeting PET imaging. Oligonucleotide aptamers are small molecular ligands that specifically bind with high affinity to their target molecules. For specific tumor imaging, an aptamer radiotracer was formulated by chelating a 64Cu isotope and DOTA-PEGylated aptamer sequence to target EpCAM. In vitro cell uptake assays demonstrated that the aptamer radiotracer specifically bound EpCAM-expressing breast cancer cells but did not react with off-target tumor cells. For in vivo tumor imaging, aptamer radiotracer was systemically administered into xenograft mice. MicroPET/CT scans revealed that the aptamer radiotracer rapidly highlighted xenograft tumors derived from MDA-MB-231 breast cancer cells (EpCAM positive) as early as 2 h postadministration with a gradually increasing tumor uptake signal that peaked at 24 h but not in lymphoma 937 tumors (EpCAM negative). In contrast, nonspecific background signals in the liver and kidneys were rapidly decreased postadministration. This proof-of-concept study demonstrates the utility of aptamer radiotracers for tumor-specific PET imaging.

Mitochondria and chronic effects of cancer therapeutics: The clinical implications.

One of the major mechanisms of action of chemo-radiation is to induce cellular senescence, which exerts crucial roles in age-related pathology. The concept of senescence is evolved, and the novel understanding of senescence-associated reprogramming/stemness has emerged. This new concept emphasizes senescence as not only cell cycle arrest but describes that subsets of senescent cells induced by chemotherapy can re-enter cell cycles, proliferate rapidly, and acquire "stemness" status. Cancer therapeutics, including chemo-radiation triggers toxicity effects through damaging mitochondria, primarily through the upregulation of mtROS production leading to subsequent mtDNA and telomeric DNA damage elicitng DNA damage responses (DDR). The ultimate goal of this review is to highlight the new concept of senescence-associated stemness that is induced by cancer treatment and its adverse effects on the vascular system. We will describe how chemo-radiation exerts toxicity effects by simultaneously producing reactive oxygen species in mitochondria and promoting DDR in the nucleus. We discuss the potential of clinical targeting poly (ADP-ribose) polymerase which might prevent downstream mitochondrial dysfunction and confer protection to cancer survivors. Overall we emphasize the importance of recognizing the consequences of cardio-toxic effects of several cancer treatments and therefore developing personalized therapeutic approaches to screen for inflammatory and cardiac testing for better patient survival.

Glycolytic Switch Is Required for Transdifferentiation to Endothelial Lineage.

BACKGROUND: We have previously shown that activation of cell-autonomous innate immune signaling facilitates the transdifferentiation of fibroblasts into induced endothelial cells, and is required to generate induced endothelial cells with high fidelity for endothelial lineage. Recent studies indicate that a glycolytic switch plays a role in induced pluripotent stem cell generation from somatic cells. METHODS: Seahorse and metabolomics flux assays were used to measure the metabolic changes during transdifferentiation in vitro, and Matrigel plug assay was used to assess the effects of glycolysis modulators on transdifferentiation in vivo. RESULTS: The metabolic switch begins rapidly after activation of innate immunity, before the expression of markers of endothelial lineage. Inhibiting glycolysis impaired, whereas facilitating glycolysis enhanced, the generation of induced endothelial cells. The toll-like receptor 3 agonist poly I:C increased expression of the mitochondrial citrate transporter Slc25A1, and the nuclear ATP-citrate lyase, in association with intracellular accumulation of citrate, the precursor for acetyl coenzyme A. These metabolic changes were coordinated with increased histone acetylation during transdifferentiation. CONCLUSION: Innate immune signaling promotes a glycolytic switch that is required for transdifferentiation, both processes being attenuated by ATP-citrate lyase knockdown. These data shed light on a novel link between metabolism and epigenetic modulation in transdifferentiation.

Developmental outcomes following prenatal exposure to methamphetamine: A Western Australian perspective.

AIM: To describe neurodevelopmental outcomes among a cohort of Western Australian infants exposed to maternal methamphetamine use during pregnancy and to determine whether the Ages and Stages Questionnaire is a reliable screening tool for this population. METHODS: Methamphetamine-using women were approached for participation when referred to the state-wide perinatal specialist drug and alcohol service for pregnancy care. Drug use during pregnancy was self-reported in each trimester using a standardised questionnaire. Ages and Stages Questionnaires were completed by infant care givers at 4 and 12 months, and development was formally assessed at 12 months using the Griffiths Mental Development Scales. Griffiths results for term-born infants in our cohort were compared to a Western Australian historical cohort of 443 healthy 1-2-year-olds. RESULTS: A total of 112 methamphetamine-using pregnant women participated in the study, who gave birth to 110 live-born infants. Ages and Stages Questionnaires were completed for 89 (81%) and 78 (71%) of the infants at 4 and 12 months, respectively. The Ages and Stages assessment identified 30 infants (33.7%) as having a potential developmental delay at 4 months and 29 infants (38.7%) as having a potential developmental delay at 12 months. Griffiths assessments were performed on 64 (58%) of the infants, with a mean general quotient of 92.7. This was significantly lower in term-born babies compared to the historical cohort (who had a median general quotient of 113.0). There was a weak correlation between 12-month Ages and Stages scores and Griffiths general quotients (r = 0.322) and no correlation between 4-month Ages and Stages Questionnaire scores and later Griffiths results. CONCLUSIONS: Infants born to women reporting methamphetamine use during pregnancy are at increased risk of developmental delay and may warrant enhanced developmental follow-up. However, they are a challenging group to follow due to complex psychosocial factors. Ages and Stages Questionnaires at 4 and 12 months were not helpful in screening for infants who had a developmental delay at 12 months.

Variability in endocrine cell identity in patients with chronic pancreatitis undergoing islet autotransplantation.

Beta-cell dedifferentiation as shown by cellular colocalization of insulin with glucagon and/or vimentin, and decreased expression of MAFA and/or urocortin3 has been suggested to contribute to metabolic decompensation in type 2 diabetes, and was recently described postimplantation in islet allotransplant patients. Dysglycaemia and diabetes mellitus are often encountered preoperatively in patients undergoing pancreatectomy and islet autotransplantation (PIAT). In this series of case reports, we document variation in islet phenotypic identity in three patients with chronic pancreatitis (CP) without diabetes or significant insulin resistance who subsequently underwent PIAT. Pancreas histology was examined using colocalization of endocrine hormones, mesenchymal and pan-endocrine markers in islets, and the relative expression of MAFA and urocortin3 in insulin-expressing cells as compared to that of nondiabetic and type 2 diabetic donors. We present results of pre- and posttransplant clinical metabolic testing. Varying degrees of islet-cell dedifferentiation are identified in nondiabetic patients with CP at the time of PIAT, and may need further investigation.

Single-Molecule Force Measurement Guides the Design of Multivalent Ligands with Picomolar Affinity.

Interaction of multiple entities and receptors, or multivalency is widely applied to achieve high affinity ligands for diagnostic and therapeutic purposes. However, lack of knowledge on receptor distribution in living subjects remains a challenge for rational structure design. Herein, we develop a force measurement platform to probe the distribution and separation of the cell surface vascular endothelial growth factor receptors (VEGFR) in live cells, and use this to assess the geometry of appropriate linkers for distinct multivalent binding modes. A tetravalent lead ZD-4, which was developed from an antitumor drug ZD6474 (Vandetanib) with combined hybrid binding effects, yielded a 2000-fold improvement in the binding affinity to VEGFR with IC50 value of 25 pm. We confirmed the improved affinity by the associated increase of tumor uptake in the VEGFR-targeting positron emission tomography (PET) imaging using U87 tumor xenograft mouse model.

Mitochondrial Function in Non-ischemic Heart Failure.

Provision for the continuous demand for energy from the beating heart relies heavily on efficient mitochondrial activity. Non-ischemic cardiomyopathy in which oxygen supply is not limiting results from etiologies such as pressure overload. It is associated with progressive development of metabolic stress culminating in energy depletion and heart failure. The mitochondria from the ventricular walls undergoing non-ischemic cardiomyopathy are subjected to long periods of adaptation to support the changing metabolic milieu, which has been described as mal-adaptation since it ultimately results in loss of cardiac contractile function. While the chronicity of exposure to metabolic stressors, co-morbidities and thereby adaptive changes in mitochondria maybe different between ischemic and non-ischemic heart failure, the resulting pathology is very similar, especially in late stage heart failure. Understanding of the mitochondrial changes in early-stage heart failure may guide the development of mitochondrial-targeted therapeutic options to prevent progression of non-ischemic heart failure. This chapter reviews findings of mitochondrial functional changes in animal models and humans with non-ischemic heart failure. While most animal models of non-ischemic heart failure exhibit cardiac mitochondrial dysfunction, studies in humans have been inconsistent despite confirmed reduction in ATP production. This chapter also reviews the possibility of impairment of substrate supply processes upstream of the mitochondria in heart failure, and discusses potential metabolism-targeted therapeutic options.

Combination of angiotensin II and l-NG-nitroarginine methyl ester exacerbates mitochondrial dysfunction and oxidative stress to cause heart failure.

Mitochondrial dysfunction has been implicated as a cause of energy deprivation in heart failure (HF). Herein, we tested individual and combined effects of two pathogenic factors of nonischemic HF, inhibition of nitric oxide synthesis [with l-N(G)-nitroarginine methyl ester (l-NAME)] and hypertension [with angiotensin II (AngII)], on myocardial mitochondrial function, oxidative stress, and metabolic gene expression. l-NAME and AngII were administered individually and in combination to mice for 5 wk. Although all treatments increased blood pressure and reduced cardiac contractile function, the l-NAME + AngII group was associated with the most severe HF, as characterized by edema, hypertrophy, oxidative stress, increased expression of Nppa and Nppb, and decreased expression of Atp2a2 and Camk2b. l-NAME + AngII-treated mice exhibited robust deterioration of cardiac mitochondrial function, as observed by reduced respiratory control ratios in subsarcolemmal mitochondria and reduced state 3 levels in interfibrillar mitochondria for complex I but not for complex II substrates. Cardiac myofibrils showed reduced ADP-supported and oligomycin-inhibited oxygen consumption. Mitochondrial functional impairment was accompanied by reduced mitochondrial DNA content and activities of pyruvate dehydrogenase and complex I but increased H2O2 production and tissue protein carbonyls in hearts from AngII and l-NAME + AngII groups. Microarray analyses revealed the majority of the gene changes attributed to the l-NAME + AngII group. Pathway analyses indicated significant changes in metabolic pathways, such as oxidative phosphorylation, mitochondrial function, cardiac hypertrophy, and fatty acid metabolism in l-NAME + AngII hearts. We conclude that l-NAME + AngII is associated with impaired mitochondrial respiratory function and increased oxidative stress compared with either l-NAME or AngII alone, resulting in nonischemic HF.

Differential Mitochondrial Function in Remodeled Right and Nonremodeled Left Ventricles in Pulmonary Hypertension.

OBJECTIVES: Right ventricular failure is the primary reason for mortality in pulmonary hypertension (PH), but little is understood about the energetics of the failing right myocardium. Our aim was to examine mitochondrial function and proteomic signatures in paired remodeled right (RM-RV) and non-remodeled left (NRM-LV) ventricular tissue samples procured during heart-lung transplantation. METHODS AND RESULTS: Contractile dysfunction in RM-RV and preserved contractile function in NRM-LV were determined clinically and by echocardiography. Mitochondria were isolated from fresh paired RV and LV wall specimens of explanted hearts. Respiratory states in response to 4 substrates and an uncoupler were analyzed. Proteomic analysis on the mitochondrial isolates was performed with the use of liquid chromatography-mass spectrometry. The RM-RV mitochondria exhibited higher succinate state 4 levels with lower respiratory control ratio (RCR) compared with state 4 levels for pyruvate-malate (PM) and glutamate-malate (GM). RM-RV mitochondria also exhibited lower state 3 for palmitoyl-carnitine (PC) and state 4 for all complex I substrates compared with NRM-LV. The mean RCR were greater in RM-RVs than in NRM-LVs for PM and GM, which is consistent with tight coupling (low state 4 rates, higher RCRs); however, low RM-RV state 3 rates suggest concurrent substrate-dependent impairment in respiratory capacity. Mitochondrial proteomics revealed greater levels of mitochondrial ADP-ATP translocase and proteins of ATP synthesis, mitochondrial pyruvate and short branched chain acyl-CoA metabolism in RM-RV. CONCLUSIONS: The mitochondrial respiration and proteomics in RM-RV are different from NRM-LV. These results have important implications in expanding our understanding of RV metabolism and future management of RV failure.

A PKM2 signature in the failing heart.

A salient feature of the failing heart is metabolic remodeling towards predominant glucose metabolism and activation of the fetal gene program. Sunitinib is a multitargeted receptor tyrosine kinase inhibitor used for the treatment of highly vascularized tumors. In diabetic patients, sunitinib significantly decreases blood glucose. However, a considerable proportion of sunitinib-treated patients develop cardiac dysfunction or failure. We asked whether sunitinib treatment results in shift towards glycolysis in the heart. Glucose uptake by the heart was increased fivefold in mice treated with sunitinib. Transcript analysis by qPCR revealed an induction of genes associated with glycolysis and reactivation of the fetal gene program. Additionally, we observed a shift in the enzyme pyruvate kinase from the adult M1 (PKM1) isoform to the fetal M2 (PKM2) isoform, a hallmark of the Warburg Effect. This novel observation led us to examine whether a similar shift occurs in human heart failure. Examination of tissue from patients with heart failure similarly displayed an induction of PKM2. Moreover, this phenomenon was partially reversed following mechanical unloading. We propose that pyruvate kinase isoform switching represents a novel feature of the fetal gene program in the failing heart.

Freshly isolated mitochondria from failing human hearts exhibit preserved respiratory function.

In heart failure mitochondrial dysfunction is thought to be responsible for energy depletion and contractile dysfunction. The difficulties in procuring fresh left ventricular (LV) myocardium from humans for assessment of mitochondrial function have resulted in the reliance on surrogate markers of mitochondrial function and limited our understanding of cardiac energetics. We isolated mitochondria from fresh LV wall tissue of patients with heart failure and reduced systolic function undergoing heart transplant or left ventricular assist device placement, and compared their function to mitochondria isolated from the non-failing LV (NFLV) wall tissue with normal systolic function from patients with pulmonary hypertension undergoing heart-lung transplant. We performed detailed mitochondrial functional analyses using 4 substrates: glutamate-malate (GM), pyruvate-malate (PM) palmitoyl carnitine-malate (PC) and succinate. NFLV mitochondria showed preserved respiratory control ratios and electron chain integrity with only few differences for the 4 substrates. In contrast, HF mitochondria had greater respiration with GM, PM and PC substrates and higher electron chain capacity for PM than for PC. Surprisingly, HF mitochondria had greater respiratory control ratios and lower ADP-independent state 4 rates than NFLV mitochondria for GM, PM and PC substrates demonstrating that HF mitochondria are capable of coupled respiration ex vivo. Gene expression studies revealed decreased expression of key genes in pathways for oxidation of both fatty acids and glucose. Our results suggest that mitochondria from the failing LV myocardium are capable of tightly coupled respiration when isolated and supplied with ample substrates. Thus energy starvation in the failing heart may be the result of dysregulation of metabolic pathways, impaired substrate supply or reduced mitochondrial number but not the result of reduced mitochondrial electron transport capacity.

Mitochondria-Targeted Oligomeric α-Synuclein Induces TOM40 Degradation and Mitochondrial Dysfunction in Parkinson's Disease and Parkinsonism-Dementia of Guam.

Mitochondrial dysfunction is a central aspect of Parkinson's disease (PD) pathology, yet the underlying mechanisms are not fully understood. This study investigates the link between α-Synuclein (α-Syn) pathology and the loss of translocase of the outer mitochondrial membrane 40 (TOM40), unraveling its implications for mitochondrial dysfunctions in neurons. We discovered that TOM40 protein depletion occurs in the brains of patients with Guam Parkinsonism Dementia (Guam PD) and cultured neurons expressing α-Syn proteinopathy, notably, without corresponding changes in TOM40 mRNA levels. Cultured neurons expressing α-Syn mutants, with or without a mitochondria-targeting signal (MTS) underscore the role of α-Syn's mitochondrial localization in inducing TOM40 degradation. Parkinson's Disease related etiological factors, such as 6-hydroxy dopamine or ROS/metal ions stress, which promote α-Syn oligomerization, exacerbate TOM40 depletion in PD patient-derived cells with SNCA gene triplication. Although α-Syn interacts with both TOM40 and TOM20 in the outer mitochondrial membrane, degradation is selective for TOM40, which occurs via the ubiquitin-proteasome system (UPS) pathway. Our comprehensive analyses using Seahorse technology, mitochondrial DNA sequencing, and damage assessments, demonstrate that mutant α-Syn-induced TOM40 loss results in mitochondrial dysfunction, characterized by reduced membrane potential, accumulation of mtDNA damage, deletion/insertion mutations, and altered oxygen consumption rates. Notably, ectopic supplementation of TOM40 or reducing pathological forms of α-Syn using ADP-ribosylation inhibitors ameliorate these mitochondrial defects, suggesting potential therapeutic avenues. In conclusion, our findings provide crucial mechanistic insights into how α-Syn accumulation leads to TOM40 degradation and mitochondrial dysfunction, offering insights for targeted interventions to alleviate mitochondrial defects in PD.

FUS unveiled in mitochondrial DNA repair and targeted ligase-1 expression rescues repair-defects in FUS-linked motor neuron disease.

This study establishes the physiological role of Fused in Sarcoma (FUS) in mitochondrial DNA (mtDNA) repair and highlights its implications to the pathogenesis of FUS-associated neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). Endogenous FUS interacts with and recruits mtDNA Ligase IIIα (mtLig3) to DNA damage sites within mitochondria, a relationship essential for maintaining mtDNA repair and integrity in healthy cells. Using ALS patient-derived FUS mutant cell lines, a transgenic mouse model, and human autopsy samples, we discovered that compromised FUS functionality hinders mtLig3's repair role, resulting in increased mtDNA damage and mutations. These alterations cause various manifestations of mitochondrial dysfunction, particularly under stress conditions relevant to disease pathology. Importantly, rectifying FUS mutations in patient-derived induced pluripotent cells (iPSCs) preserves mtDNA integrity. Similarly, targeted introduction of human DNA Ligase 1 restores repair mechanisms and mitochondrial activity in FUS mutant cells, suggesting a potential therapeutic approach. Our findings unveil FUS's critical role in mitochondrial health and mtDNA repair, offering valuable insights into the mechanisms underlying mitochondrial dysfunction in FUS-associated motor neuron disease.

The efficacy and safety of burosumab in two patients with cutaneous skeletal hypophosphatemia syndrome.

Cutaneous skeletal hypophosphatemia syndrome (CSHS) is an ultra-rare mosaic disorder manifesting as skeletal dysplasia and FGF23-mediated hypophosphatemia, with some experiencing extra-osseous/extra-cutaneous manifestations, including both benign and malignant neoplasms. Like other disorders of FGF23-mediated hypophosphatemia including X-linked hypophosphatemia (XLH) and tumor-induced osteomalacia (TIO), patients with CSHS have low serum phosphorus and active 1,25-dihydroxyvitamin D levels. Current treatment options for patients with CSHS include multiple daily doses of oral phosphorus and one or more daily doses of active vitamin D analog to correct the deficits. Recently, the fully human monoclonal antibody against FGF23 burosumab received US approval for the treatment of XLH and TIO, two rare diseases characterized by FGF23-mediated hypophosphatemia leading to rickets and osteomalacia. Given the similarities between the pathobiologies of these disorders and CSHS, we investigated the impact of burosumab on two patients, one pediatric and one adult, with CSHS who participated in separate, but similarly designed trials. In both the pediatric and adult patients, burosumab therapy was well-tolerated and contributed to clinically meaningful improvements in disease outcomes including normalization of phosphorus metabolism and markers of bone health, and improvements in skeletal abnormalities, fractures, and physical function. Reported adverse events were minimal, with only mild injection site reactions attributed to burosumab therapy. Together, these findings suggest that burosumab therapy is a promising therapeutic option for patients with CSHS.

FUS Unveiled in Mitochondrial DNA Repair and Targeted Ligase-1 Expression Rescues Repair-Defects in FUS-Linked Neurodegeneration.

This study establishes the physiological role of Fused in Sarcoma (FUS) in mitochondrial DNA (mtDNA) repair and highlights its implications to the pathogenesis of FUS-associated neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS). Endogenous FUS interacts with and recruits mtDNA Ligase IIIα (mtLig3) to DNA damage sites within mitochondria, a relationship essential for maintaining mtDNA repair and integrity in healthy cells. Using ALS patient-derived FUS mutant cell lines, a transgenic mouse model, and human autopsy samples, we discovered that compromised FUS functionality hinders mtLig3's repair role, resulting in increased mtDNA damage and mutations. These alterations cause various manifestations of mitochondrial dysfunction, particularly under stress conditions relevant to disease pathology. Importantly, rectifying FUS mutations in patient-derived induced pluripotent cells (iPSCs) preserves mtDNA integrity. Similarly, targeted introduction of human DNA Ligase 1 restores repair mechanisms and mitochondrial activity in FUS mutant cells, suggesting a potential therapeutic approach. Our findings unveil FUS's critical role in mitochondrial health and mtDNA repair, offering valuable insights into the mechanisms underlying mitochondrial dysfunction in FUS-associated neurodegeneration.