Ageing is associated with a reduction in markers of mitochondrial energy metabolism in the human epidermis

The decline of mitochondrial function throughout the lifespan is directly linked to the development of ageing phenotypes of the skin. Here, we assessed alterations in markers of epidermal mitochondrial energy metabolism as a function of skin age. Human skin samples from distinct anatomical regions were obtained during routine dermatological surgery from 21 young (27.6 ± 1.71 year) and 22 old (76.2 ± 1.73 year) donors. Sections of skin samples were analysed by immunohistochemistry for mitochondrial subunits of each electron transport chain complex (I-V)/oxidative phosphorylation (OXPHOS), as well as proteins serving as a marker of mitochondrial mass (VDAC1) and the regulation of DNA transcription (TFAM). Staining intensities of ATP5F1A (comprising complex V) and TFAM in the epidermis of older subjects were significantly decreased compared with younger donors. Moreover, these effects were independent of UV exposure of the stained skin section. Overall, we demonstrate that ageing is associated with reduced protein levels of complex V of the mitochondrial respiratory chain and TFAM. These alterations may impair essential mitochondrial functions, exacerbating the cutaneous ageing process.

Characterising a homozygous two-exon deletion in UQCRH: comparing human and mouse phenotypes

Mitochondrial disorders are clinically and genetically diverse, with isolated complex III (CIII) deficiency being relatively rare. Here, we describe two affected cousins, presenting with recurrent episodes of severe lactic acidosis, hyperammonaemia, hypoglycaemia and encephalopathy. Genetic investigations in both cases identified a homozygous deletion of exons 2 and 3 of UQCRH, which encodes a structural complex III (CIII) subunit. We generated a mouse model with the equivalent homozygous Uqcrh deletion (Uqcrh-/- ), which also presented with lactic acidosis and hyperammonaemia, but had a more severe, non-episodic phenotype, resulting in failure to thrive and early death. The biochemical phenotypes observed in patient and Uqcrh-/- mouse tissues were remarkably similar, displaying impaired CIII activity, decreased molecular weight of fully assembled holoenzyme and an increase of an unexpected large supercomplex (SXL ), comprising mostly of one complex I (CI) dimer and one CIII dimer. This phenotypic similarity along with lentiviral rescue experiments in patient fibroblasts verifies the pathogenicity of the shared genetic defect, demonstrating that the Uqcrh-/- mouse is a valuable model for future studies of human CIII deficiency.

Splenoportal-mesenteric axis thrombosis and splenic artery occlusion as initial presentations of COVID-19 disease

OBJECTIVE

Although pulmonary involvement represents the primary and most characteristic presentation of Sars-Cov-2 infection, due to its innate tropism for endothelium, it is also associated with systemic pro-coagulative changes and thromboses. This paper describes a COVID-19 atypical presentation with massive thrombotic occlusion of the splenoportal-mesenteric axis and the splenic artery in the absence of clinical or radiological manifestation of pulmonary involvement.

PATIENTS AND METHODS

Female patient, with no history of disease, trauma or fever in the last 30 days, was admitted to ER for persistent left subcostal pain. Laboratory exams, including inflammation, coagulation markers and Sars-CoV-2 serology, were requested. Whole-body CT with contrast media injection was performed.

RESULTS

Laboratory exams showed elevated reactive C-protein, bilirubin, γ-GT and D-dimer. Whole-body CT showed: splenic artery occlusion, thrombosis of splenic, mesenteric and portal veins with portal intra-hepatic branches ectasia, juxta-hilar portal cavernomatosis of probable acute onset (absence of signs of chronic hepatopathy and of varices), a hypodense area in the spleen indicating ischemic parenchymal suffering. The patient resulted positive for Sars-CoV-2 IgG, thus in the absence of typical clinics or pulmonary parenchymal abnormality at chest CT.

CONCLUSIONS

A case of acute venous thrombosis and arterial occlusion as primary manifestations of COVID-19.

Mitochondrial energy metabolism is negatively regulated by cannabinoid receptor 1 in intact human epidermis

Epidermal energy metabolism is relevant to skin physiology, ageing and photodamage. While selected hormones stimulate epidermal keratinocyte mitochondrial activity, its negative regulation remains unknown. In several cell types, cannabinoid receptor 1 (CB₁ ) is expressed both on the cell membrane (cmCB₁ ) and on the mitochondrial outer membrane (mtCB₁ ), where its stimulation directly suppresses mitochondrial functions. In the current pilot study, we investigated if CB₁ is a negative regulator of human epidermal energy metabolism under physiological conditions. Using organ-cultured full-thickness human skin specimens of healthy individuals, we showed that antagonizing the homeostatic CB₁ signalling by the administration of the CB₁ inverse agonist AM251 increased respiratory chain complex I and II/IV activity. The effect was CB₁ -dependent, since the CB₁ -selective agonist arachidonyl-2'-chloroethylamide could prevent the effect. Moreover, the phenomenon was also reproduced by siRNA-mediated down-regulation of CB₁ . As revealed by the unaltered expression of several relevant markers (TFAM, VDAC1, MTCO1 and NDUFS4), modulation of CB₁ signalling had no effect on the epidermal mitochondrial mass. Next, by using immunoelectron microscopy, we found that human epidermal keratinocytes express both cmCB₁ and mtCB₁ . Finally, by using equipotent extracellularly restricted (hemopressin) as well as cell-permeable (AM251) inverse agonists, we found that mitochondrial activity is most likely exclusively regulated by mtCB₁ . Thus, our data identify mtCB₁ as a novel negative regulator of keratinocyte mitochondrial activity in intact human epidermis, and raise the question, whether topical therapeutic interventions capable of selectively activating mtCB₁ can reduce excessive mitochondrial ROS production resulting from dysregulated mitochondrial activity during skin ageing or photodamage.

From old to new - Repurposing drugs to target mitochondrial energy metabolism in cancer

Although we have entered the era of personalized medicine and tailored therapies, drugs that target a large variety of cancers regardless of individual patient differences would be a major advance nonetheless. This review article summarizes current concepts and therapeutic opportunities in the area of targeting aerobic mitochondrial energy metabolism in cancer. Old drugs previously used for diseases other than cancer, such as antibiotics and antidiabetics, have the potential to inhibit the growth of various tumor entities. Many drugs are reported to influence mitochondrial metabolism. However, here we consider only those drugs which predominantly inhibit oxidative phosphorylation.

Lithium and Not Acetoacetate Influences the Growth of Cells Treated with Lithium Acetoacetate

The ketogenic diet (KD), a high-fat/low-carbohydrate/adequate-protein diet, has been proposed as a treatment for a variety of diseases, including cancer. KD leads to generation of ketone bodies (KBs), predominantly acetoacetate (AcAc) and 3-hydroxy-butyrate, as a result of fatty acid oxidation. Several studies investigated the antiproliferative effects of lithium acetoacetate (LiAcAc) and sodium 3-hydroxybutyrate on cancer cells in vitro. However, a critical point missed in some studies using LiAcAc is that Li ions have pleiotropic effects on cell growth and cell signaling. Thus, we tested whether Li ions per se contribute to the antiproliferative effects of LiAcAc in vitro. Cell proliferation was analyzed on neuroblastoma, renal cell carcinoma, and human embryonic kidney cell lines. Cells were treated for 5 days with 2.5, 5, and 10 mM LiAcAc and with equimolar concentrations of lithium chloride (LiCl) or sodium chloride (NaCl). LiAcAc affected the growth of all cell lines, either negatively or positively. However, the effects of LiAcAc were always similar to those of LiCl. In contrast, NaCl showed no effects, indicating that the Li ion impacts cell proliferation. As Li ions have significant effects on cell growth, it is important for future studies to include sources of Li ions as a control.

Inducing cancer indolence by targeting mitochondrial Complex I is potentiated by blocking macrophage-mediated adaptive responses

Converting carcinomas in benign oncocytomas has been suggested as a potential anti-cancer strategy. One of the oncocytoma hallmarks is the lack of respiratory complex I (CI). Here we use genetic ablation of this enzyme to induce indolence in two cancer types, and show this is reversed by allowing the stabilization of Hypoxia Inducible Factor-1 alpha (HIF-1α). We further show that on the long run CI-deficient tumors re-adapt to their inability to respond to hypoxia, concordantly with the persistence of human oncocytomas. We demonstrate that CI-deficient tumors survive and carry out angiogenesis, despite their inability to stabilize HIF-1α. Such adaptive response is mediated by tumor associated macrophages, whose blockage improves the effect of CI ablation. Additionally, the simultaneous pharmacological inhibition of CI function through metformin and macrophage infiltration through PLX-3397 impairs tumor growth in vivo in a synergistic manner, setting the basis for an efficient combinatorial adjuvant therapy in clinical trials.

Lack of Galanin Receptor 3 Alleviates Psoriasis by Altering Vascularization, Immune Cell Infiltration, and Cytokine Expression

The neuropeptide galanin is distributed in the central and peripheral nervous systems and in non-neuronal peripheral organs, including the skin. Galanin acts via three G protein-coupled receptors which, except galanin receptor 1, are expressed in various skin structures. The galanin system has been associated with inflammatory processes of the skin and of several other organs. Psoriasis is an inflammatory skin disease with increased neovascularization, keratinocyte hyperproliferation, a proinflammatory cytokine milieu, and immune cell infiltration. In this study, we showed that galanin receptor 3 is present in endothelial cells in human and murine dermal vessels and is co-expressed with nestin in neo-vessels of psoriatic patients. Moreover, in a murine psoriasis model, we showed that C57/BL6 mice lacking galanin receptor 3 display a milder course of psoriasis upon imiquimod treatment, leading to decreased disease severity, delayed neo-vascularization, reduced infiltration of neutrophils, and significantly lower levels of proinflammatory cytokines compared with wild-type mice. In contrast, galanin receptor 2-knockout animals did not differ significantly from wild type mice at both the macroscopic and molecular levels in their inflammatory response to imiquimod treatment. Our data indicate that galanin receptor 3, but not galanin receptor 2, plays an important role in psoriasis-like skin inflammation.

A ketogenic diet supplemented with medium-chain triglycerides enhances the anti-tumor and anti-angiogenic efficacy of chemotherapy on neuroblastoma xenografts in a CD1-nu mouse model

Neuroblastoma (NB) is a pediatric malignancy characterized by a marked reduction in aerobic energy metabolism. Recent preclinical data indicate that targeting this metabolic phenotype by a ketogenic diet (KD), especially in combination with calorie restriction, slows tumor growth and enhances metronomic cyclophosphamide (CP) therapy of NB xenografts. Because calorie restriction would be contraindicated in most cancer patients, the aim of the present study was to optimize the KD such that the tumors are sensitized to CP without the need of calorie restriction. In a NB xenograft model, metronomic CP was combined with KDs of different triglyceride compositions and fed to CD1-nu mice ad libitum. Metronomic CP in combination with a KD containing 8-carbon medium-chain triglycerides exerted a robust anti-tumor effect, suppressing growth and causing a significant reduction of tumor blood-vessel density and intratumoral hemorrhage, accompanied by activation of AMP-activated protein kinase in NB cells. Furthermore, the KDs caused a significant reduction in the serum levels of essential amino acids, but increased those of serine, glutamine and glycine. Our data suggest that targeting energy metabolism by a modified KD may be considered as part of a multimodal treatment regimen to improve the efficacy of classic anti-NB therapy.

Effects of alpha-melanocyte-stimulating hormone on mitochondrial energy metabolism in rats of different age-groups

Hypothalamic alpha-melanocyte-stimulating hormone (α-MSH) is a key catabolic mediator of energy homeostasis. Its anorexigenic and hypermetabolic effects show characteristic age-related alterations that may be part of the mechanism of middle-aged obesity and geriatric anorexia/cachexia seen in humans and other mammals. We aimed to investigate the role of α-MSH in mitochondrial energy metabolism during the course of aging in a rodent model. To determine the role of α-MSH in mitochondrial energy metabolism in muscle, we administered intracerebroventricular (ICV) infusions of α-MSH for 7-days to different age-groups of male Wistar rats. The activities of oxidative phosphorylation complexes I to V and citrate synthase were determined and compared to those of age-matched controls. We also quantified mitochondrial DNA (mtDNA) copy number and measured the expression of the master regulators of mitochondrial biogenesis, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and peroxisome proliferator-activated receptor gamma (PPARγ). The peptide reduced weight gain in juvenile rats to one fifth of that of controls and increased the weight loss in older animals by about five fold. Mitochondrial DNA copy number inversely correlated with changes in body weight in controls, but not in α-MSH-treated animals. The strong increase in body weight in young rats was associated with a low mtDNA copy number and high PPARγ mRNA levels in controls. Expression of PGC-1α and PPARγ declined with age, whereas OXPHOS and citrate synthase enzyme activities were unchanged. In contrast, α-MSH treatment suppressed OXPHOS enzyme and citrate synthase activity. In conclusion, our results showed age-related differences in the metabolic effects of α-MSH. In addition, administration of α-MSH suppressed citrate synthase and OXPHOS activities independent of age. These findings suggest that α-MSH exposure may inhibit mitochondrial biogenesis.

Thyroid Hormones Enhance Mitochondrial Function in Human Epidermis

Since it is unknown whether thyroid hormones (THs) regulate mitochondrial function in human epidermis, we treated organ-cultured human skin, or isolated cultured human epidermal keratinocytes, with triiodothyronine (100 pmol/L) or thyroxine (100 nmol/L). Both THs significantly increased protein expression of the mitochondrially encoded cytochrome C oxidase I (MTCO1), complex I activity, and the number of perinuclear mitochondria. Triiodothyronine also increased mitochondrial transcription factor A (TFAM) protein expression, and thyroxine stimulated complex II/IV activity. Increased mitochondrial function can correlate with increased reactive oxygen species production, DNA damage, and accelerated tissue aging. However, THs neither raised reactive oxygen species production or matrix metalloproteinase-1, -2 and -9 activity nor decreased sirtuin1 (Sirt1) immunoreactivity. Instead, triiodothyronine increased sirtuin-1, fibrillin-1, proliferator-activated receptor-gamma 1-alpha (PGC1α), collagen I and III transcription, and thyroxine decreased cyclin-dependent kinase inhibitor 2A (p16(ink4)) expression in organ-cultured human skin. Moreover, TH treatment increased intracutaneous fibrillin-rich microfibril and collagen III deposition and decreased mammalian target of rapamycin (mTORC1/2) expression ex vivo. This identifies THs as potent endocrine stimulators of mitochondrial function in human epidermis, which down-regulates rather than enhance the expression of skin aging-related biomarkers ex vivo. Therefore, topically applied THs deserve further exploration as candidate agents for treating skin conditions characterized by reduced mitochondrial function.

Mitochondria: The ketogenic diet--A metabolism-based therapy

Mitochondria are the energy-producing organelles of the cell, generating ATP via oxidative phosphorylation mainly by using pyruvate derived from glycolytic processing of glucose. Ketone bodies generated by fatty acid oxidation can serve as alternative metabolites for aerobic energy production. The ketogenic diet, which is high in fat and low in carbohydrates, mimics the metabolic state of starvation, forcing the body to utilize fat as its primary source of energy. The ketogenic diet is used therapeutically for pharmacoresistant epilepsy and for "rare diseases" of glucose metabolism (glucose transporter type 1 and pyruvate dehydrogenase deficiency). As metabolic reprogramming from oxidative phosphorylation toward increased glycolysis is a hallmark of cancer cells; there is increasing evidence that the ketogenic diet may also be beneficial as an adjuvant cancer therapy by potentiating the antitumor effect of chemotherapy and radiation treatment. This article is part of a Directed Issue entitled: Energy Metabolism Disorders and Therapies.

Energy metabolism in neuroblastoma and Wilms tumor

To support high proliferation, the majority of cancer cells undergo fundamental metabolic changes such as increasing their glucose uptake and shifting to glycolysis for ATP production at the expense of far more efficient mitochondrial energy production by oxidative phosphorylation (OXPHOS), which at first glance is a paradox. This phenomenon is known as the Warburg effect. However, enhanced glycolysis is necessary to provide building blocks for anabolic growth. Apart from the generation of ATP, intermediates of glycolysis serve as precursors for a variety of biosynthetic pathways essential for cell proliferation. In the last 10-15 years the field of tumor metabolism has experienced an enormous boom in interest. It is now well established that tumor suppressor genes and oncogenes often play a central role in the regulation of cellular metabolism. Therefore, they significantly contribute to the manifestation of the Warburg effect. While much attention has focused on adult solid tumors, so far there has been comparatively little effort directed at elucidation of the mechanism responsible for the Warburg effect in childhood cancers. In this review we focus on metabolic pathways in neuroblastoma (NB) and Wilms tumor (WT), the two most frequent solid tumors in children. Both tumor types show alterations of the OXPHOS system and glycolytic features. Chromosomal alterations and activation of oncogenes like MYC or inactivation of tumor suppressor genes like TP53 can in part explain the changes of energy metabolism in these cancers. The strict dependence of cancer cells on glucose metabolism is a fairly common feature among otherwise biologically diverse types of cancer. Therefore, inhibition of glycolysis or starvation of cancer cells through glucose deprivation via a high-fat low-carbohydrate diet may be a promising avenue for future adjuvant therapeutic strategies.

Tumour necrosis factor alpha, interferon gamma and substance P are novel modulators of extrapituitary prolactin expression in human skin

Human scalp skin and hair follicles (HFs) are extra-pituitary sources of prolactin (PRL). However, the intracutaneous regulation of PRL remains poorly understood. Therefore we investigated whether well-recognized regulators of pituitary PRL expression, which also impact on human skin physiology and pathology, regulate expression of PRL and its receptor (PRLR) in situ. This was studied in serum-free organ cultures of microdissected human scalp HFs and skin, i.e. excluding pituitary, neural and vascular inputs. Prolactin expression was confirmed at the gene and protein level in human truncal skin, where its expression significantly increased (p = 0.049) during organ culture. There was, however, no evidence of PRL secretion into the culture medium as measured by ELISA. PRL immunoreactivity (IR) in female human epidermis was decreased by substance P (p = 0.009), while neither the classical pituitary PRL inhibitor, dopamine, nor corticotropin-releasing hormone significantly modulated PRL IR in HFs or skin respectively. Interferon (IFN) γ increased PRL IR in the epithelium of human HFs (p = 0.044) while tumour necrosis factor (TNF) α decreased both PRL and PRLR IR. This study identifies substance P, TNFα and IFNγ as novel modulators of PRL and PRLR expression in human skin, and suggests that intracutaneous PRL expression is not under dopaminergic control. Given the importance of PRL in human hair growth regulation and its possible role in the pathogenesis of several common skin diseases, targeting intracutaneous PRL production via these newly identified regulatory pathways may point towards novel therapeutic options for inflammatory dermatoses.