Thyroxine differentially modulates the peripheral clock: lessons from the human hair follicle

The human hair follicle (HF) exhibits peripheral clock activity, with knock-down of clock genes (BMAL1 and PER1) prolonging active hair growth (anagen) and increasing pigmentation. Similarly, thyroid hormones prolong anagen and stimulate pigmentation in cultured human HFs. In addition they are recognized as key regulators of the central clock that controls circadian rhythmicity. Therefore, we asked whether thyroxine (T4) also influences peripheral clock activity in the human HF. Over 24 hours we found a significant reduction in protein levels of BMAL1 and PER1, with their transcript levels also decreasing significantly. Furthermore, while all clock genes maintained their rhythmicity in both the control and T4 treated HFs, there was a significant reduction in the amplitude of BMAL1 and PER1 in T4 (100 nM) treated HFs. Accompanying this, cell-cycle progression marker Cyclin D1 was also assessed appearing to show an induced circadian rhythmicity by T4 however, this was not significant. Contrary to short term cultures, after 6 days, transcript and/or protein levels of all core clock genes (BMAL1, PER1, clock, CRY1, CRY2) were up-regulated in T4 treated HFs. BMAL1 and PER1 mRNA was also up-regulated in the HF bulge, the location of HF epithelial stem cells. Together this provides the first direct evidence that T4 modulates the expression of the peripheral molecular clock. Thus, patients with thyroid dysfunction may also show a disordered peripheral clock, which raises the possibility that short term, pulsatile treatment with T4 might permit one to modulate circadian activity in peripheral tissues as a target to treat clock-related disease

A practical guide for the study of human and murine sebaceous glands in situ

The skin of most mammals is characterised by the presence of sebaceous glands (SGs), whose predominant constituent cell population is sebocytes, that is, lipid-producing epithelial cells, which develop from the hair follicle. Besides holocrine sebum production (which contributes 90% of skin surface lipids), multiple additional SG functions have emerged. These range from antimicrobial peptide production and immunomodulation, via lipid and hormone synthesis/metabolism, to the provision of an epithelial progenitor cell reservoir. Therefore, in addition to its involvement in common skin diseases (e.g. acne vulgaris), the unfolding diversity of SG functions, both in skin health and disease, has raised interest in this integral component of the pilosebaceous unit. This practical guide provides an introduction to SG biology and to relevant SG histochemical and immunohistochemical techniques, with emphasis placed on in situ evaluation methods that can be easily employed. We propose a range of simple, established markers, which are particularly instructive when addressing specific SG research questions in the two most commonly investigated species in SG research, humans and mice. To facilitate the development of reproducible analysis techniques for the in situ evaluation of SGs, this methods review concludes by suggesting quantitative (immuno-)histomorphometric methods for standardised SG evaluation

The Effects of Pregnenolone 16α-Carbonitrile Dosing on Digoxin Pharmacokinetics and Intestinal Absorption in the Rat

The effect of Pgp induction in rats by pregnenolone 16α-carbonitrile (PCN) (3 days, 35 mg/kg/d, p.o.) on digoxin pharmacokinetics and intestinal transport has been assessed. After intravenous or oral digoxin dosing the arterial and hepatic portal vein (oral) AUC(0-24h) were significantly reduced by PCN pre-treatment. Biliary digoxin clearance increased 2-fold following PCN treatment. PCN significantly increased net digoxin secretion (2.05- and 4.5-fold respectively) in ileum and colon but not in duodenum or jejunum. This increased secretion correlated with increased Pgp protein expression in ileum and colon. Both intestinal and biliary excretion therefore contribute to altered digoxin disposition following PCN

Author Correction: Organic osmolytes preserve the function of the developing tight junction in ultraviolet B-irradiated rat epidermal keratinocytes

From Springer Nature via Jisc Publications RouterHistory: registration 2020-05-06, pub-electronic 2020-05-20, online 2020-05-20, collection 2020-12Publication status: PublishedAn amendment to this paper has been published and can be accessed via a link at the top of the paper

Cholesterol homeostasis in hair follicle keratinocytes is disrupted by impaired ABCA5 activity

The importance of cholesterol in hair follicle biology is underscored by its links to the pathogenesis of alopecias and hair growth disorders. Reports have associated defects in ABCA5, a membrane transporter, with altered keratinocyte cholesterol distribution in individuals with a form of congenital hypertrichosis, yet the biological basis for this defect in hair growth remains unknown. This study aimed to determine the impact of altered ABCA5 activity on hair follicle keratinocyte behaviour. Primary keratinocytes isolated from the outer root sheath of plucked human hair follicles were utilised as a relevant cell model. Following exogenous cholesterol loading, an increase in ABCA5 co-localisation to intracellular organelles was seen. Knockdown of ABCA5 revealed a dysregulation in cholesterol homeostasis, with LXR agonism leading to partial restoration of the homeostatic response. Filipin staining and live BODIPY cholesterol immunofluorescence microscopy revealed a reduction in endo-lysosomal cholesterol following ABCA5 knockdown. Analysis of oxysterols showed a significant increase in the fold change of 25-hydroxycholesterol and 7-β-hydroxycholesterol following cholesterol loading in ORS keratinocytes, after ABCA5 knockdown. These data suggest a role for ABCA5 in the intracellular compartmentalisation of free cholesterol in primary hair follicle keratinocytes. The loss of normal homeostatic response, following the delivery of excess cholesterol after ABCA5 knockdown, suggests an impact on LXR-mediated transcriptional activity. The loss of ABCA5 in the hair follicle could lead to impaired endo-lysosomal cholesterol transport, impacting pathways known to influence hair growth. This avenue warrants further investigation. [Abstract copyright: Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.

ATES national tool

The UK has a vast, largely untapped, low-enthalpy geothermal potential in shallow aquifers. To date, there are over 3000 shallow schemes exploiting heat and cool stored in aquifer systems across the world, with the majority of these schemes installed and successfully operating in alluvial gravels in the Netherlands. A much smaller number of schemes are located in north-west Europe, Turkey, USA, Canada, China and Japan. There are only 11 Aquifer Thermal Energy schemes in the UK, although suitable geology to host schemes is not considered a barrier to wider adoption. The geology that is considered particularly suitable for ATES schemes includes both permeable Superficial Deposits (glacial and post-glacial), and importantly Bedrock Aquifers which typically have high groundwater storativity, transmissivity and production rates at levels required to support medium to large output ATES doublet systems. Here, we describe the first national-scale assessment of the potential thermal energy storage represented by bedrock aquifers in the UK (including England, Northern Ireland, Scotland and Wales), assuming a nominal 0.5 MW doublet scheme with a maximum change in groundwater temperature of 10 degrees C resulting in a minimum required flowrate per well of at least 10 l/s. These conditions restricted the assessment to 6 Principal Aquifers including the Triassic and Permian sandstones, Permian Dolomites, the Inferior and Great Oolite groups, the Lower Greensand and the Chalk Group. Using a combination of surface and subsurface mapping, we provide an interactive GIS layer showing general information including the spatial distribution of suitable aquifers, and the number of aquifers that may be encountered to a depth of 400 m on a 1 km grid. We additionally map on published heat and cool densities for each unit area to illustrate the potential requirements across the UK. This assessment does not consider some parameters that are best considered at a local-scale such as variability in aquifer properties including groundwater chemistry, groundwater gradients, extraction and injection flow rates and thus storage capacities. The tool indicates that the UK has extensive spatial coverage of geology that is suitable for the development and utilisation of medium to large scale ATES systems. There is a strong juxtaposition between ATES suitable geological bedrock units and mapped heating and cooling density particularly across south-east, midlands, and north-west England, and parts of Northern Ireland; there are limited opportunities in Scotland. Overall, there is significant potential for the development of ATES within the UK to meet desired carbon reduction targets. This assessment only considers single medium to large ATES doublets and as such the required flow rates are achievable from the aquifer are the principal constraining factor. Engineering alternative systems with multiple doublets of lower output and requiring lower yield rates would allow a significantly greater proportion of the bedrock geology/areas of the country to support the deployment of ATES systems. There are many opportunities for open-loop ATES systems in locations close to areas of anticipated high demand, such as urban and industrial areas. Aquifer Thermal Energy Storage therefore represents an important thermal management opportunity for the UK that can be integrated into a portfolio of low-carbon energy technologies that will be required to support the stated net-zero ambitions at National, regional and local scales

Oxidative damage control in a human (mini-) organ: Nrf2 activation protects against oxidative stress-induced hair growth inhibition

The in situ control of redox insult in human organs is of major clinical relevance, yet remains incompletely understood. Activation of Nrf2, the “master regulator” of genes controlling cellular redox homeostasis, is advocated as a therapeutic strategy for diseases with severely impaired redox balance. It remains to be shown whether this strategy is effective in human organs, rather than isolated human cell types. We have therefore explored the role of Nrf2 in a uniquely accessible human (mini-) organ, human scalp hair follicles (HFs). Microarray and qPCR analysis of human HFs following Nrf2 activation using sulforaphane identified the modulation of phase II metabolism, ROS clearance, the pentose phosphate pathway and glutathione homeostasis. Nrf2 knockdown (siRNA) in cultured human HFs confirmed the regulation of key Nrf2 target genes (i.e. HO-1, NQO1, GSR, GCLC, ABCC1, PRDX1). Importantly, Nrf2 activation significantly reduced ROS levels and associated lipid peroxidation. Nrf2 pre-activation reduced oxidative stress-stimulated (H2O2 or menadione) premature catagen and hair growth inhibition, significantly ameliorated the H2O2-dependent increase in matrix keratinocyte apoptosis and reversed the ROS-induced reduction in proliferation. This study thus provides direct evidence for the crucial role of Nrf2 in protecting human organ function (i.e. scalp HFs) against redox insult

A Clinical and Biological Guide for Understanding Chemotherapy-Induced Alopecia and its Prevention

Chemotherapy-induced alopecia (CIA) is the most visibly distressing side effect of commonly administered chemotherapeutic agents. As psychological health has huge relevance on lifestyle, diet and self-esteem, it is important for clinicians to fully appreciate the psychological burden that CIA can place on patients. Here, for the first time, we provide a comprehensive review encompassing the molecular characteristics of the human hair follicle (HF), how different anticancer agents damage the HF to cause CIA, subsequent HF pathophysiology and we assess known and emerging prevention modalities that have aimed to reduce or prevent CIA. We argue that, at present, scalp cooling is the only safe and FDA-cleared modality available, and we highlight the extensive available clinical and experimental (biological) evidence for its efficacy. The likelihood of a patient that uses scalp cooling during chemotherapy maintaining enough hair to not require a wig is approximately 50%. This is despite different types of chemotherapy regimens, patient-specific differences and possible lack of staff experience in effectively delivering scalp cooling. The increased use of scalp cooling and an understanding of how to deliver it most effectively to patients has enormous potential to ease the psychological burden of CIA, until other, more efficacious, equally safe treatments become available