Biology subjects

Pitts, K.

Publications and source records attributed to Pitts, K..

3 recordsLinked to original sources

bioRxiv2025

A Non-canonical Role for Hepatocyte MLKL in Promoting Mitochondrial Dysfunction and Senescence in the Aging Liver

Liver aging is characterized by chronic inflammation and metabolic dysfunction that contributes to the progression of metabolic dysfunction-associated steatotic liver disease (MASLD). Necroptosis, a form of inflammatory cell death, is activated in aging livers, and genetic (Ripk3-/-or Mlkl-/- mice) or pharmacological (RIPK1 inhibitor necrostatin-1s) inhibition of necroptosis attenuates liver inflammation and pathology. However, the cell type-specific role of necroptosis in liver aging remains unclear. Given that MLKL is expressed in hepatocytes, and its expression increases with age, we generated hepatocyte-specific MLKL-overexpressing mice (MLKLHepOE) to determine its role in liver aging. Unexpectedly, MLKL overexpression in hepatocytes did not induce necroptosis, but instead upregulated markers of cellular senescence (cell cycle arrest genes and SASP factors), increased macrophage infiltration, and elevated M1 macrophage marker expression. Electron microscopy and mitochondrial analyses revealed abnormal mitochondrial morphology, elevated oxidative stress, and disrupted mitochondrial dynamics, while lipidomics demonstrated alterations in hepatic lipid metabolites. In agreement with our observations in MLKLHepOE mice, MLKL overexpression in AML12 hepatocytes impaired mitochondrial respiration, increased proinflammatory extracellular vesicle (EV) release, and induced senescence markers, without triggering cell death. Together, these findings reveal a non-lethal, non-necroptotic role for MLKL in promoting hepatocyte senescence and metabolic dysfunction via mitochondrial impairment and EV-mediated inflammation. Our study highlights MLKL as a novel driver of liver inflammaging and a potential therapeutic target for age-related liver disease.

cell biology↗

bioRxiv2024

Epigenetic adaptation drives monocyte differentiation into microglia-like cells upon engraftment into the retina

The identification of specific markers to distinguish resident microglia from infiltrating monocytes has been a long-standing challenge in neuroscience. Recently, proteins such as P2RY12, TMEM119, and FCRLS have been proposed as microglia-specific and are now widely used to define microglial populations in health and disease. The specificity of these markers was predicated on the assumption that circulating monocytes retain their distinct signatures after entering the central nervous system (CNS). Here, we challenge this paradigm. Using a combination of bone marrow chimeras, single-cell RNA sequencing, ATAC-seq, flow cytometry, and immunohistochemistry, we demonstrate that monocytes engrafting into the CNS acquire de novo expression of these established microglia markers. This phenotypic conversion is driven by profound epigenetic reprogramming, characterized by dynamic changes in chromatin accessibility at key gene loci, including P2ry12, Tmem119, and Aif1 (Iba1), and a shift in transcription factor binding motifs toward a microglial profile. We show this process occurs in the retina following injury and, remarkably, under physiological conditions in the brain and spinal cord, where blood-derived monocytes progressively contribute to the resident myeloid pool. Furthermore, engrafted monocytes downregulate canonical monocyte markers (Ly6C, CD45), eventually becoming indistinguishable from embryonic microglia based on conventional phenotyping. Our findings reveal that infiltrating monocytes undergo extensive epigenetic and transcriptional remodeling to adopt a microglia-like fate, challenging the specificity of current markers and necessitating a re-evaluation of the distinct roles of these two cell populations in CNS pathology. Significance StatementDistinguishing resident CNS microglia from infiltrating monocytes is fundamental to understanding neuro-inflammation. This study reveals that widely used "microglia-specific" markers are not exclusive, as monocytes entering the central nervous system are epigenetically reprogrammed to express them. This mimicry invalidates long-held assumptions about microglial identity and demonstrates that many cells previously identified as microglia may have a peripheral origin. Our work underscores the critical need for more reliable methods to differentiate these populations to accurately define their respective contributions to CNS health and disease.

immunology↗

bioRxiv2021

Metabolomics of healthy and stony coral tissue loss disease affected Montastraea cavernosa corals

Stony coral tissue loss disease, first observed in Florida in 2014, has now spread along the entire Florida Reef Tract and on reefs in many Caribbean countries. The disease affects a variety of coral species with differential outcomes, and in many instances results in whole-colony mortality. We employed untargeted metabolomic profiling of Montastraea cavernosa corals affected by stony coral tissue loss disease to identify metabolic markers of disease. Herein, extracts from apparently healthy, diseased, and recovered corals, Montastraea cavernosa, collected at a reef site near Ft. Lauderdale, Florida were subjected to liquid-chromatography mass spectrometry-based metabolomics. Unsupervised principal component analysis reveals wide variation in metabolomic profiles of healthy corals of the same species, which differ from diseased corals. Using a combination of supervised and unsupervised data analyses tools, we describe metabolite features that explain variation between the apparently healthy corals, between diseased corals, and between the healthy and the diseased corals. By employing a culture-based approach, we assign sources of a subset of these molecules to the endosymbiotic dinoflagellates, Symbiodiniaceae. Specifically, we identify various endosymbiont-specific lipid classes, such as betaine lipids, glycolipids, and tocopherols, which differentiate samples taken from apparently healthy corals and diseased corals. Given the variation observed in metabolite fingerprints of corals, our data suggests that metabolomics is a viable approach to link metabolite profiles of different coral species with their susceptibility and resilience to numerous coral diseases spreading through reefs worldwide.

systems biology↗