Biology subjects

Chiou, S.

Publications and source records attributed to Chiou, S..

6 recordsLinked to original sources

bioRxiv2026

Necroptotic Signalling Diverts Keratinocyte Fate to Promote Differentiation and Slow Wound Healing

Necroptosis is best known as a lytic, proinflammatory cell-death pathway mediated by RIPK3 and MLKL. Effective wound repair requires the rapid resolution of inflammation, and ongoing necroptotic activity would only exacerbate tissue damage, delaying healing. However, damaged skin presents a trigger-rich environment for necroptotic signalling, an apparent paradox that remains unresolved. Using genetic ablation and pharmacological inhibition across multiple wound models, we show that inhibiting necroptosis accelerates wound closure, revealing that necroptotic signalling normally restrains repair. Surprisingly, we found that MLKL activation in wild-type keratinocytes induces differentiation and membrane repair rather than cell lysis. This adaptive, non-lethal mode of necroptotic signalling preserves barrier integrity but slows re-epithelialisation. Our findings redefine epidermal necroptotic signalling as a stress-responsive program that modulates keratinocyte fate in a trigger-rich environment. Temporarily dampening this pathway may enhance regeneration after barrier loss without compromising immune defence, revealing necroptosis as a tunable mechanism balancing tissue repair and inflammation.

cell biology↗

bioRxiv2025

PERINATAL ORGANOPHOSPHATE FLAME RETARDANT EXPOSURE ALTERS ADULT HPA AXIS FUNCTION AND AVOIDANCE BEHAVIOR IN A SEX-SPECIFIC MANNER IN MICE

Organophosphate flame retardants (OPFRs) are ubiquitous flame-retardant additives with endocrine-disrupting properties. Despite increasing evidence that OPFRs impact neurodevelopment, their effects on the neuroendocrine stress response remain poorly understood. To examine their long-term impact on stress regulation, we treated pregnant C57Bl/6J dams to a mixture of tris(1,3-dichloro-2-propyl) phosphate (TDCPP), triphenyl phosphate (TPP), and tricresyl phosphate (TCP; 1 mg/kg each) from gestational day (GD) 7 through postnatal day (PND) 14. Adult offspring (8-9 weeks of age) were then challenged with acute stressors, including 1 h restraint or a 6-day acute variable stress (AVS) paradigm. Perinatal OPFR exposure produced persistent, sex-specific alterations in the hypothalamic-pituitary-adrenal (HPA) axis and stress-related neurocircuitry. Following 1 h restraint, OPFR-treated females showed heightened serum corticosterone. In addition, gene expression analysis revealed sex-dependent disruptions in key stress-regulatory pathways after OPFR treatment and 1 h restraint in the hypothalamus (Crhr1, Crhr2, Ptpn5) and pituitary (Crhr1, Pomc, Nr3c1). Females demonstrated more differences in adrenal gene expression related to steroidogenesis (Mc2r, Cyp11b2) and catecholamine biosynthesis (Dbh, Pnmt), with OPFR-treated groups having blunted responses. OPFR AVS females displayed reduced corticosterone and Crh mRNA in the hypothalamus, and downregulated Pacap/Pac1r expression in the bed nucleus of the stria terminalis (BNST), accompanied by increased behavioral avoidance and immobility. In males, OPFR exposure led to increased BNST Pacap and Pac1r, expression, along with hyperactivity and avoidance behaviors. Together, these findings demonstrate that early-life OPFR exposure induces lasting, sex-specific dysregulation of the HPA axis and associated stress circuits, highlighting OPFRs as developmental neuroendocrine disruptors with implications for mood and stress-related disorders.

neuroscience↗

bioRxiv2025

The kinase domain of RIPK3 tunes its scaffolding functions

The pro-inflammatory programmed cell death pathway, necroptosis, relies on phosphorylation of the terminal effector, MLKL, by RIPK3. RIPK3-deficient mice or those harboring the kinase-inactivating mutation, RIPK3K51A, are ostensibly normal in the absence of challenge, indicating that RIPK3 and its kinase activity are dispensable for development. However, another kinase-inactivating mutation, RIPK3D161N, results in embryonic lethality in mice due to widespread apoptosis. As a result, the RIPK3D161N mutation is thought to confer a toxic gain-of-function. Here, to further explore the impacts of RIPK3 inactivation, we compared the stability and cellular interactions of RIPK3D161N and RIPK3K51A to a third previously-uncharacterized kinase-dead variant, RIPK3D143N. Here, we show that RIPK3K51A was unstable and did not associate with RIPK1, RIPK3D161N was unstable but interacted with RIPK1, whereas RIPK3D143N was stable and bound RIPK1 in a manner comparable to wild-type RIPK3. Thus, all three variants scaffold differently, suggesting that the assembly of cell death machinery by RIPK3 is finely tuned, not just by its kinase activity, but also by the conformation of its kinase domain. Physiologically, Ripk3D143N/D143N mice exhibited a partially penetrant lethality in utero. However, once born, Ripk3D143N/D143N mice were fertile and phenotypically indistinguishable from wild-type mice in the absence of challenge, with RIPK3D143N mutation protecting mice lacking intestinal epithelial Caspase-8 from necroptotic ileitis. Our studies support the idea that RIPK3 is a nexus between apoptotic and necroptotic signaling, and highlight the importance of considering kinase domain conformation in RIPK3 inhibitor development.

biochemistry↗

bioRxiv2023

An immunohistochemical atlas of necroptotic pathway expression

Necroptosis is a lytic form of regulated cell death reported to contribute to inflammatory diseases of the gut, skin and lung, as well as ischemic-reperfusion injuries of the kidney, heart and brain. However, precise identification of the cells and tissues that undergo necroptotic cell death in vivo has proven challenging in the absence of robust protocols for immunohistochemical detection. Here, we provide automated immunohistochemistry protocols to detect core necroptosis regulators - Caspase-8, RIPK1, RIPK3 and MLKL - in formalin-fixed mouse and human tissues. We observed surprising heterogeneity in protein expression within tissues, whereby short-lived immune barrier cells were replete with necroptotic effectors, whereas long-lived cells lacked RIPK3 or MLKL expression. Local changes in the expression of necroptotic effectors occurred in response to insults such as inflammation, dysbiosis or immune challenge, consistent with necroptosis being dysregulated in disease contexts. These methods will facilitate the precise localisation and evaluation of necroptotic signaling in vivo. HighlightsO_LI13 automated immunohistochemistry protocols for detecting the necroptotic pathway C_LIO_LINecroptotic pathway expression is confined to fast-cycling immune barriers C_LIO_LINecroptotic pathway expression changes at sites of immunoinflammatory challenge C_LIO_LIImmunodetection of necrosomes in IBD patients is a putative new diagnostic tool C_LI

cell biology↗

bioRxiv2022

MLKL deficiency protects against low-grade, sterile inflammation in aged mice

MLKL and RIPK3 are the core signaling proteins of the inflammatory cell death pathway, necroptosis, which is a known mediator and modifier of human disease. Necroptosis has been implicated in the progression of disease in almost every physiological system and recent reports suggest a role for necroptosis in aging. Here we present the first comprehensive analysis of age-related histopathological and immunological phenotypes in a cohort of Mlkl-/- and Ripk3-/- mice on a congenic C57BL/6J genetic background. We show that genetic deletion of Mlkl, but not Ripk3, in female mice interrupts immune system aging, specifically delaying the age-related reduction of circulating lymphocytes. Mlkl-/- female mice were also protected against age-related, low-grade chronic sterile inflammation, with a reduced number of inflammatory infiltrates present in the connective and muscle tissue at 17 months relative to wild-type littermates. These observations implicate MLKL in age-related sterile inflammation, suggesting a possible application for long-term anti-necroptotic therapy in humans.

immunology↗

bioRxiv2022

A common human MLKL polymorphism confers resistance to negative regulation by phosphorylation

Across the globe, 2-3% of humans carry the p.Ser132Pro single nucleotide polymorphism in MLKL, the terminal effector protein of the inflammatory form of programmed cell death, necroptosis. We show that this substitution confers a gain in necroptotic function in human cells, with more rapid accumulation of activated MLKLS132P in biological membranes and MLKLS132P overriding pharmacological and endogenous inhibition of MLKL. In mouse cells, the equivalent Mlkl S131P mutation confers a gene dosage dependent reduction in sensitivity to TNF-induced necroptosis in both hematopoietic and non-hematopoietic cells, but enhanced sensitivity to IFN-{beta} induced death in non-hematopoietic cells. In vivo, MlklS131P homozygosity reduces the capacity to clear Salmonella from major organs and retards recovery of hematopoietic stem cells. Thus, by dysregulating necroptosis, the S131P substitution impairs the return to homeostasis after systemic challenge. Present day carriers of the MLKL S132P polymorphism may be the key to understanding how MLKL and necroptosis modulate the progression of complex polygenic human disease.

immunology↗