An optimised protocol for the detection of lipofuscin, a versatile and quantifiable marker of cellular senescence.

Lipofuscin is a yellow-brown pigment typically found in the lysosomes that contains a mixture of molecules including lipids, metals and misfolded proteins. The use of Sudan black B to detect lipofuscin accumulation, a well described marker of cellular senescence and ageing, was first described in 2013 by Georgakopoulou, et al. Here, we provide an optimisation of the original protocol. Firstly, we adjusted the staining methodology for increased ease of use on cultured cells. Secondly, we show that Sudan black B-stained lipofuscin emits strong fluorescence in the far-red channel making it suitable for fluorescence microscopy detection and quantification. Moreover, we also demonstrate that this optimised protocol can be utilised in conjunction with standard immunofluorescence staining techniques, making possible the simultaneous detection of lipofuscin and other cellular proteins of interest, like additional markers of senescence. This is a significant advantage over the most commonly used method for senescence detection, based on beta galactosidase enzymatic activity. We therefore believe that these findings and the provided optimised protocol will represent a useful tool for the scientific community in the field of cellular senescence.

In Silico and In Vitro Analysis of IL36RN Alterations Reveals Critical Residues for the Function of the Interleukin-36 Receptor Complex.

Generalized pustular psoriasis is a potentially life-threatening skin disease, associated with IL36RN disease alleles. IL36RN encodes the IL-36 receptor antagonist (IL-36Ra), a protein that downregulates the activity of IL-36 cytokines by blocking their receptor (IL-36R). Although generalized pustular psoriasis can be treated with IL-36R inhibitors, the structural underpinnings of the IL-36Ra/IL-36R interaction remain poorly understood. In this study, we sought to address this question by systematically investigating the effects of IL36RN sequence changes. We experimentally characterized the effects of 30 IL36RN variants on protein stability. In parallel, we used a machinelearning tool (Rhapsody) to analyze the IL-36Ra three-dimensional structure and predict the impact of all possible amino acid substitutions. This integrated approach identified 21 amino acids that are essential for IL-36Ra stability. We next investigated the effects of IL36RN changes on IL-36Ra/IL-36R binding and IL-36R signaling. Combining invitro assays and machine learning with a second program (mCSM), we identified 13 amino acids that are critical for IL-36Ra/IL36R engagement. Finally, we experimentally validated three representative predictions, further confirming the reliability of Rhapsody and mCSM. These findings shed light on the structural determinants of IL-36Ra activity, with potential to facilitate the design of new IL-36 inhibitors and aid the interpretation of IL36RN variants in diagnostic settings.

Melanocortin therapies to resolve fibroblast-mediated diseases.

Stromal cells have emerged as central drivers in multiple and diverse diseases, and consequently, as potential new cellular targets for the development of novel therapeutic strategies. In this review we revise the main roles of fibroblasts, not only as structural cells but also as players and regulators of immune responses. Important aspects like fibroblast heterogeneity, functional specialization and cellular plasticity are also discussed as well as the implications that these aspects may have in disease and in the design of novel therapeutics. An extensive revision of the actions of fibroblasts on different conditions uncovers the existence of numerous diseases in which this cell type plays a pathogenic role, either due to an exacerbation of their 'structural' side, or a dysregulation of their 'immune side'. In both cases, opportunities for the development of innovative therapeutic approaches exist. In this regard, here we revise the existing evidence pointing at the melanocortin pathway as a potential new strategy for the treatment and management of diseases mediated by aberrantly activated fibroblasts, including scleroderma or rheumatoid arthritis. This evidence derives from studies involving models of in vitro primary fibroblasts, in vivo models of disease as well as ongoing human clinical trials. Melanocortin drugs, which are pro-resolving mediators, have shown ability to reduce collagen deposition, activation of myofibroblasts, reduction of pro-inflammatory mediators and reduced scar formation. Here we also discuss existing challenges, both in approaching fibroblasts as therapeutic targets, and in the development of novel melanocortin drug candidates, that may help advance the field and deliver new medicines for the management of diseases with high medical needs.

Senescence under appraisal: hopes and challenges revisited.

In recent years, cellular senescence has become the focus of attention in multiple areas of biomedical research. Typically defined as an irreversible cell cycle arrest accompanied by increased cellular growth, metabolic activity and by a characteristic messaging secretome, cellular senescence can impact on multiple physiological and pathological processes such as wound healing, fibrosis, cancer and ageing. These unjustly called 'zombie cells' are indeed a rich source of opportunities for innovative therapeutic development. In this review, we collate the current understanding of the process of cellular senescence and its two-faced nature, i.e. beneficial/detrimental, and reason this duality is linked to contextual aspects. We propose the senescence programme as an endogenous pro-resolving mechanism that may lead to sustained inflammation and damage when dysregulated or when senescent cells are not cleared efficiently. This pro-resolving model reconciles the paradoxical two faces of senescence by emphasising that it is the unsuccessful completion of the programme, and not senescence itself, what leads to pathology. Thus, pro-senescence therapies under the right context, may favour inflammation resolution. We also review the evidence for the multiple therapeutic approaches under development based on senescence, including its induction, prevention, clearance and the use of senolytic and senomorphic drugs. In particular, we highlight the importance of the immune system in the favourable outcome of senescence and the implications of an inefficient immune surveillance in completion of the senescent cycle. Finally, we identify and discuss a number of challenges and existing gaps to encourage and stimulate further research in this exciting and unravelled field, with the hope of promoting and accelerating the clinical success of senescence-based therapies.