Arachidonic acid hyperpolarizes mesenchymal stromal cells from the human adipose tissue by stimulating TREK1 K+ channels

Lipidomics reveals cell specific changes during pluripotent differentiation to neural and mesodermal lineages

Due to their self-renewal and differentiation capabilities, pluripotent stem cells hold immense potential for advancing our understanding of human disease and developing cell-based or pharmacological interventions. Realizing this potential, however, requires a thorough understanding of the basal cellular mechanisms which occur during differentiation. Lipids are critical molecules that define the morphological, biochemical, and functional role of cells. This, combined with emerging evidence linking lipids to neurodegeneration, cardiovascular health, and other diseases, makes lipids a critical class of analytes to assess normal and abnormal cellular processes. While previous work has examined the lipid composition of stem cells, uncertainties remain about which changes are conserved and which are unique across distinct cell types. In this study, we investigated lipid alterations of induced pluripotent stem cells (iPSCs) at critical stages of differentiation toward neural or mesodermal fates. Lipidomic analyses of distinct differentiation stages were completed using a platform coupling liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS) separations. Results illustrated a shared triacylglyceride and free fatty acid accumulation in early iPSCs that were utilized at different stages of differentiation. Unique fluctuations through differentiation were also observed for certain phospholipid classes, sphingomyelins, and ceramides. These insights into lipid fluctuations across iPSC differentiation enhance our fundamental understanding of lipid metabolism within pluripotent stem cells and during differentiation, while also paving the way for a more precise and effective application of pluripotent stem cells in human disease interventions.

Lipidomics Reveals Cell Specific Changes During Pluripotent Differentiation to Neural and Mesodermal Lineages

Due to their self-renewal and differentiation capabilities, pluripotent stem cells hold immense potential for advancing our understanding of human disease and developing cell-based or pharmacological interventions. Realizing this potential, however, requires a thorough understanding of the basal cellular mechanisms which occur during differentiation. Lipids are critical molecules that define the morphological, biochemical, and functional role of cells. This, combined with emerging evidence linking lipids to neurodegeneration, cardiovascular health, and other diseases, makes lipids a critical class of analytes to assess normal and abnormal cellular processes. While previous work has examined the lipid composition of stem cells, uncertainties remain about which changes are conserved and which are unique across distinct cell types. In this study, we investigated lipid alterations of induced pluripotent stem cells (iPSCs) at critical stages of differentiation toward neural or mesodermal fates. Lipdiomic analyses of distinct differentiation stages were completed using a platform coupling liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS) separations. Results illustrated a shared triacylglyceride and free fatty acid accumulation in early iPSCs that were utilized at different stages of differentiation. Unique fluctuations through differentiation were also observed for certain phospholipid classes, sphingomyelins and ceramides. These insights into lipid fluctuations across iPSC differentiation enhance our fundamental understanding of lipid metabolism within pluripotent stem cells and during differentiation, while also paving the way for a more precise and effective application of pluripotent stem cells in human disease interventions.

Ostruthin, a TWIK-Related Potassium Channel Agonist, Increases the Body Temperature in Ovariectomized Rats With or Without Progesterone Administration

BACKGROUND AND OBJECTIVES

The TWIK-related potassium (TREK) channel subfamily, including TREK1 and TREK2, is a novel cold receptor. Ostruthin, a TREK1 and TREK2 agonist, is a component found in the plant Paramignya trimera and is traditionally used as an anticancer medicine in Vietnam, with its stems and roots treating various ailments. The female hormone progesterone (P4) influences body temperature in women; however, the effect of P4 on thermoregulation via TREK has not been examined. This study aims to investigate the effects of P4 on thermoregulatory responses in ostruthin-administered ovariectomized rats, which are animal models of human menopause.

METHODS

Wistar rats were ovariectomized and implanted with silastic tubes with or without P4 (P4(+) and P4(-) groups). The TREK agonist or vehicle was injected intraperitoneally. Body temperature, locomotor activity, tail skin temperature, and thermoregulatory behavior (assessed by tail-hiding behavior) were continuously measured. Plasma concentrations of catecholamines, triiodothyronine, and thyroxine were also measured.

RESULTS

In both the P4(+) and P4(-) groups, the change in body temperature was greater among the rats administered the TREK agonist compared to the vehicle. No significant differences were observed between the groups in locomotor activity, tail skin temperature, or tail-hiding behavior. The dopamine concentration in the P4(+) group was lower than that in the P4(-) group.

CONCLUSIONS

Ostruthin, the TREK agonist, increases body temperature in ovariectomized rats; however, P4 may not affect these responses in ovariectomized rats.

Polythiophene-mediated light modulation of membrane potential and calcium signalling in human adipose-derived stem/stromal cells

Recent progress in the fields of regenerative medicine and tissue engineering has been strongly fostered both by the investigation of crucial cues, able to trigger the regeneration of damaged tissues, and by the development of ad hoc functional materials, capable of selectively (re-)activating relevant physiological pathways. In parallel to the successful realization of biochemical cues and the optimization of delivery protocols, the use of biophysical stimuli has been emerging as an alternative, highly effective strategy. Techniques based on electrical, magnetic and mechanical stimulation have been reported to efficiently direct differentiation of stem cells and modulate cell physiology at different developmental stages. In this framework, the use of optical stimulation represents a valuable approach, possibly overcoming current limitations of chemical cues, like limited spatial and temporal resolution and poor control over the extracellular environment. Surprisingly, the effects of light on the physiological properties (light toxicity, cell membrane potential, and cell ionic trafficking) of undifferentiated cells, as well as on their differentiation pathways, were investigated to a very limited extent and rarely quantified in a systematic way. In this work, we aim at clarifying the effects of optical excitation on the physiological behaviour of undifferentiated human adipose-derived stem cells (hASC), cultured on top of a light-sensitive conjugated polymer, region-regular poly-3-hexyl-thiophene (P3HT). Interestingly, we observe statistically significant modulation of the cell membrane potential, as well as noticeable effects on intracellular calcium signalling, triggered by P3HT excitation upon green light stimuli. Possible mechanisms involved in the signal transduction pathways are considered and critically discussed. The capability to modulate the physiological response of hASC upon photoexcitation, in a highly controlled and selective manner, provides a promptly available and non invasive diagnostic tool, thus contributing to the understanding of the complex machinery behind stem cells and material interfaces. Moreover, it may open the route to novel techniques to drive the differentiation path with unprecedented versatility and operational easiness.

Negative Influence by the Force: Mechanically Induced Hyperpolarization via K2P Background Potassium Channels

The two-pore domain K_2P subunits form background (leak) potassium channels, which are characterized by constitutive, although not necessarily constant activity, at all membrane potential values. Among the fifteen pore-forming K_2P subunits encoded by the KCNK genes, the three members of the TREK subfamily, TREK-1, TREK-2, and TRAAK are mechanosensitive ion channels. Mechanically induced opening of these channels generally results in outward K⁺ current under physiological conditions, with consequent hyperpolarization and inhibition of membrane potential-dependent cellular functions. In the past decade, great advances have been made in the investigation of the molecular determinants of mechanosensation, and members of the TREK subfamily have emerged among the best-understood examples of mammalian ion channels directly influenced by the tension of the phospholipid bilayer. In parallel, the crucial contribution of mechano-gated TREK channels to the regulation of membrane potential in several cell types has been reported. In this review, we summarize the general principles underlying the mechanical activation of K_2P channels, and focus on the physiological roles of mechanically induced hyperpolarization.

TRPM2 Oxidation Activates Two Distinct Potassium Channels in Melanoma Cells through Intracellular Calcium Increase

Tumor microenvironments are often characterized by an increase in oxidative stress levels. We studied the response to oxidative stimulation in human primary (IGR39) or metastatic (IGR37) cell lines obtained from the same patient, performing patch-clamp recordings, intracellular calcium ([Ca²⁺]_i) imaging, and RT-qPCR gene expression analysis. In IGR39 cells, chloramine-T (Chl-T) activated large K⁺ currents (KROS) that were partially sensitive to tetraethylammonium (TEA). A large fraction of KROS was inhibited by paxilline—a specific inhibitor of large-conductance Ca²⁺-activated BK channels. The TEA-insensitive component was inhibited by senicapoc—a specific inhibitor of the Ca²⁺-activated KCa3.1 channel. Both BK and KCa3.1 activation were mediated by an increase in [Ca²⁺]_i induced by Chl-T. Both KROS and [Ca²⁺]_i increase were inhibited by ACA and clotrimazole—two different inhibitors of the calcium-permeable TRPM2 channel. Surprisingly, IGR37 cells did not exhibit current increase upon the application of Chl-T. Expression analysis confirmed that the genes encoding BK, KCa3.1, and TRPM2 are much more expressed in IGR39 than in IGR37. The potassium currents and [Ca²⁺]_i increase observed in response to the oxidizing agent strongly suggest that these three molecular entities play a major role in the progression of melanoma. Pharmacological targeting of either of these ion channels could be a new strategy to reduce the metastatic potential of melanoma cells, and could complement classical radio- or chemotherapeutic treatments.