Hyperbaric oxygen alters intracellular bioenergetics distribution in human dermal fibroblasts

Physiological skin oxygen levels: An important criterion for skin cell functionality and therapeutic approaches

The skin is made up of different layers with various gradients, which maintain a complex microenvironment, particularly in terms of oxygen levels. However, all types of skin cells are cultured in conventional incubators that do not reproduce physiological oxygen levels. Instead, they are cultured at atmospheric oxygen levels, a condition that is far removed from physiology and may lead to the generation of free radicals known to induce skin ageing. This review aims to summarize the current literature on the effect of physiological oxygen levels on skin cells, highlight the shortcomings of current in vitro models, and demonstrate the importance of respecting skin oxygen levels. We begin by clarifying the terminology used about oxygen levels and describe the specific distribution of oxygen in the skin. We review and discuss how skin cells adapt their oxygen consumption and metabolism to oxygen levels environment, as well as the changes that are induced, particularly, their redox state, life cycle and functions. We examine the effects of oxygen on both simple culture models and more complex reconstructed skin models. Finally, we present the implications of oxygen modulation for a more therapeutic approach.

Hyperoxic exposure alters intracellular bioenergetics distribution in human pulmonary cells

AIMS

Pulmonary oxygen toxicity is caused by exposure to a high fraction of inspired oxygen, which damages multiple cell types within the lung. The cellular basis for pulmonary oxygen toxicity includes mitochondrial dysfunction. The aim of this study was to identify the effects of hyperoxic exposure on mitochondrial bioenergetic and dynamic functions in pulmonary cells.

MAIN METHODS

Mitochondrial respiration, inner membrane potential, dynamics (including motility), and distribution of mitochondrial bioenergetic capacity in two intracellular regions were quantified using cultured human lung microvascular endothelial cells, human pulmonary artery endothelial cells and A549 cells. Hyperoxic (95 % O₂) exposures lasted 24, 48 and 72 h, durations relevant to mechanical ventilation in intensive care settings.

KEY FINDINGS

Mitochondrial motility was altered following all hyperoxic exposures utilized in experiments. Inhomogeneities in inner membrane potential and respiration parameters were present in each cell type following hyperoxia. The partitioning of ATP-linked respiration was also hyperoxia-duration and cell type dependent. Hyperoxic exposure lasting 48 h or longer provoked the largest alterations in mitochondrial motility and the greatest decreases in ATP-linked respiration, with a suggestion of decreases in respiration complex protein levels.

SIGNIFICANCE

Hyperoxic exposures of different durations produce intracellular inhomogeneities in mitochondrial dynamics and bioenergetics in pulmonary cells. Oxygen therapy is utilized commonly in clinical care and can induce undesirable decrements in bioenergy function needed to maintain pulmonary cell function and viability. There may be adjunctive or prophylactic measures that can be employed during hyperoxic exposures to prevent the mitochondrial dysfunction that signals the presence of oxygen toxcity.

Mitochondrial dynamics involves molecular and mechanical events in motility, fusion and fission

Mitochondria are cell organelles that play pivotal roles in maintaining cell survival, cellular metabolic homeostasis, and cell death. Mitochondria are highly dynamic entities which undergo fusion and fission, and have been shown to be very motile in vivo in neurons and in vitro in multiple cell lines. Fusion and fission are essential for maintaining mitochondrial homeostasis through control of morphology, content exchange, inheritance of mitochondria, maintenance of mitochondrial DNA, and removal of damaged mitochondria by autophagy. Mitochondrial motility occurs through mechanical and molecular mechanisms which translocate mitochondria to sites of high energy demand. Motility also plays an important role in intracellular signaling. Here, we review key features that mediate mitochondrial dynamics and explore methods to advance the study of mitochondrial motility as well as mitochondrial dynamics-related diseases and mitochondrial-targeted therapeutics.

Whey Derivatives and Galactooligosaccharides Stimulate the Wound Healing and the Function of Human Keratinocytes through the NF-kB and FOXO-1 Signaling Pathways

Skin repair requires the activation of keratinocytes and is mediated by controlled inflammation and cell migration and proliferation, ending with the regeneration of well-differentiated cell layers. Whey derivatives contain galactooligosaccharides (GOS), which have potential beneficial effects on wound healing due to their activity as toll-like receptor ligands, although their direct nonprebiotic effects in the skin have not yet been described. In this study, we investigated the effects of different whey-derived products and purified GOS on a human keratinocyte cell line. We found that the inflammatory cytokine interleukin-8 (IL-8) was upregulated by nuclear factor kappa B (NF-kB) signaling triggered by whey derivatives and GOS and that wound healing was accelerated by promoting cell migration and the loss of E-cadherin in the absence of epithelial–mesenchymal transition. Interestingly, the treatments enhanced the mitochondrial function in association with the translocation of the Forkhead Box O1 (FOXO-1) transcription factor. Finally, we detected the increased expression of the differentiation markers induced by GOS and whey derivatives. All together, our results show that GOS-containing products can promote wound closure and skin health by direct activity on keratinocyte functions. Among the preparations tested, the fermented compound produced by autochthonous microorganisms was the most active in modulating keratinocyte activity, supporting the biological value of whey derivatives for health.