Biology subjects

Rizzo, S.

Publications and source records attributed to Rizzo, S..

9 recordsLinked to original sources

bioRxiv2026

Spatial proteomic profiling of cardiac stromal populations and microenvironments in systemic sclerosis-associated primary myocardial involvement

Objectives: To define cardiac stromal heterogeneity and spatial stromal-immune organization in systemic sclerosis-associated virus-negative myocarditis (SSc-VNM), a manifestation of primary SSc heart involvement. Methods: Imaging mass cytometry, a single-cell multiplexed spatial proteomic technology, was applied to endomyocardial biopsies from ten patients with SSc-VNM, seven with VNM associated with other systemic autoimmune rheumatic diseases (a-VNM) and nine with isolated VNM (i-VNM). Single-cell phenotyping, cellular-neighborhood and spatial-interaction analyses, and correlations with histological fibrosis were performed at patient level. Results: Among 82,673 segmented cells, we identified seven fibroblast phenotypes and one CD34+ stromal-cell population. The overall fibroblast/stromal compartment was expanded in SSc-VNM compared with i-VNM (adjusted p = 0.00973). The composition of fibroblasts/stromal cells differed profoundly in SSc-VNM compared with a-VNM and i-VNM, with numerical increases in CD34+ stromal cells and SOX9+ and PI16high/POSTNhigh fibroblasts and de-enrichment of FAPhigh/POSTNhigh fibroblasts and myofibroblasts. Spatial analysis identified ten cellular neighborhoods and revealed distinct SSc-VNM-associated patterns, including altered stromal-immune interaction networks. These included enriched interactions of CD34+ stromal cells and PI16high/POSTNhigh fibroblasts with CD163high/HLA-DR+ macrophages and CD68+ mast cells. PI16high/POSTNhigh and PI16-/POSTNhigh fibroblasts demonstrated the highest collagen type 1 expression among all stromal cell subsets across all VNM entities and PI16high/POSTNhigh fibroblasts were numerically increased in biopsies with [≥]10% fibrotic remodeling and were spatially associated with collagen-rich areas. Conclusions: Our findings refine current concepts of human fibrotic myocardial remodeling and support therapeutic targeting of specific stromal players such as POSTNhigh fibroblast subpopulations. Keywords: Systemic Sclerosis; Myocarditis; Myocardial Fibrosis; Fibroblasts; Imaging Mass Cytometry.

bioinformatics↗

bioRxiv2026

Development of a nanomedicine approach to improve the therapeutic index of bexarotene.

Bexarotene (BEX), a retinoid X receptor (RXR) agonist, has demonstrated therapeutic potential in oncology, neurodegenerative diseases and inflammatory conditions, including multiple sclerosis (MS). However, its broader clinical application is limited by poor aqueous solubility, low bioavailability, and dose-limiting adverse effects, most notably hypertriglyceridaemia. In this study, we investigated whether conjugation of BEX to dextrin, a biodegradable polysaccharide, could improve its physicochemical properties and therapeutic index. A dextrin-BEX conjugate was synthesised using succinoylated dextrin (30 mol%) and characterised by gel permeation chromatography (GPC), Fourier-transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (1H-NMR) and dynamic light scattering (DLS). The effects of conjugation on solubility, aggregation behaviour and biological activity were evaluated using in vitro cytotoxicity assays in leukaemia, liver and fibroblast cell lines, alongside measurements of intracellular triglyceride levels. The impact on lipid metabolism and toxicity was further assessed in an in vivo murine model of hyperlipidaemia. Dextrin conjugation significantly increased the aqueous solubility of BEX (from <0.004 mg/mL to 9.88 mg/mL) and led to the formation of nanoscale aggregates in solution. This was associated with a marked increase in in vitro potency, with IC50 values reduced by up to 14-fold across multiple cell lines. However, the increased cytotoxicity was not selective for cancer cells and was also observed in normal fibroblast and hepatic cell models. The dextrin-BEX conjugate did not induce intracellular triglyceride accumulation in vitro. In vivo, dextrin conjugation did not mitigate BEX-associated lipid dysregulation, while serum triglyceride levels and markers of liver injury remained unchanged. However, although free BEX led to a significant increase in liver weight after 14 days, the dextrin-BEX conjugate did not produce a statistically significant effect. In conclusion, dextrin conjugation markedly improves the solubility and in vitro potency of BEX but does not enhance its selectivity or reduce its metabolic toxicity in vivo. These findings suggest that while polymer conjugation is an effective strategy for addressing physicochemical limitations, it is insufficient to overcome the inherent dyslipidaemia associated with systemic RXR activation. Future strategies should focus on integrating targeting and controlled release mechanisms, alongside approaches that address the underlying pharmacological drivers of lipid dysregulation.

pharmacology and toxicology↗

bioRxiv2026

Identifying Novel Estrogenic Mitochondrial Targets in Hypothalamic Proopiomelanocortin Neurons by Chemoproteomics

Loss of estrogens at menopause is linked to impaired brain metabolism and increased risk of Alzheimers disease (AD). However, estrogen replacement therapies are limited due to the deleterious effects of estrogen on peripheral organs and increased risk of vascular dementia. We have developed a non-steroidal estrogenic compound, STX, which does not bind to the classical estrogen receptors and {beta}, but mimics estrogenic signaling in the central nervous system (CNS) without the peripheral reproductive actions. STX is protective against neurodegeneration in stroke and AD models, but its molecular targets are unknown. Here, we identified and validated STX neural targets using chemoproteomic, molecular biological, electrophysiological and metabolic assays of hypothalamic proopiomelanocortin (POMC) neurons. Chemoproteomic profiling identified voltage dependent anion channels (VDAC1-3) as major intracellular binding partners in mHypo43 (POMC) cells. Based on quantitative single-cell PCR, Vdac2 was identified as the dominant isoform in female hypothalamic POMC neurons. Seahorse metabolic flux analyses showed that STX potently increased glycolysis, oxidative respiration and mitochondrial ATP production in mHypo43 cells. Nanomolar concentrations of STX enhanced VDAC2 voltage-dependent gating in reconstituted lipid membranes and shifted the low-conductance states toward anion selectivity, consistent with increased ATP flux. Together, these findings reveal a mechanism for the neuroprotective effects of STX through enhancing mitochondrial bioenergetics and modulating VDAC channel properties, potentially increasing cellular energy stores. Therefore, this work identifies previously unrecognized estrogenic mitochondrial targets and provides a mechanistic basis for the neuroprotective actions of STX relevant to menopause-associated brain vulnerability.

neuroscience↗

bioRxiv2026

Systems modeling identifies phenotype-determining signaling pathways controlled by phosphatase PTPRJ in diverse receptor tyrosine kinase activation settings

Protein tyrosine phosphatase receptor J (PTPRJ) restrains cell proliferation and migration by dephosphorylating receptor tyrosine kinases (RTKs) including the epidermal growth factor receptor (EGFR). PTPRJ is a purported tumor suppressor, and alterations to its expression and/or function are associated with colorectal, breast, lung, and other cancers. While there is interest in controlling PTPRJ-regulated phenotypes, efforts are limited by the complexity of PTPRJ-mediated signaling. PTPRJ dephosphorylates multiple RTKs, and the degree to which PTPRJ control of signaling and phenotypes depends on local cellular RTK activation profiles is unknown. To probe the context dependence of PTPRJ signaling regulation, we collected signaling measurements across 16 pathway nodes at two time points in a panel of HSC3 carcinoma cells engineered with different PTPRJ expression profiles. Cells were treated with three different RTK ligands, and paired phenotype measurements (viability, wound healing, xCELLigence cell index) were made. Partial least squares regression models were developed to predict relationships between PTPRJ-regulated signaling pathways and cell phenotypes. The model effectively separated contributions to variance arising from the PTPRJ expression background and growth factor context. In testing model predictions, we demonstrated that PTPRJ suppressed MET-induced cell cell proliferation via regulation of a HER3/AKT signaling axis that stabilized PTPRJ expression through an unanticipated feedback mechanism. We also found that PTPRJ regulated HSC3 cell migration via JNK signaling that was preferentially activated by MET. Our results identify new regulatory nodes through which PTPRJ influences cancer cell phenotypes and demonstrates that these processes preferentially occur in the context of distinct RTK activation states.

systems biology↗

bioRxiv2026

Rational design of a protein-protein interaction inhibitor that activates Protein Tyrosine Phosphatase 1B.

Reversible inactivation of protein tyrosine phosphatases by reactive oxygen species (ROS) is essential to the phosphorylation of growth factor receptors. An important outcome of the inactivation of protein tyrosine phosphatase 1B (PTP1B) by ROS involves the conformational change of its phosphotyrosine binding loop which adopts a solvent exposed position in its oxidized form. We previously demonstrated that 14-3-3{zeta} binds to the phosphotyrosine binding loop of the oxidized form of PTP1B. Using a rational approach, we developed a unique protein-protein interaction (PPI) inhibitor peptide derived from the phosphotyrosine binding loop of PTP1B designed to disrupt the interaction between PTP1B and the 14-3-3{zeta}-complex. Exploiting this cell-permeable peptide, we showed decreased association between PTP1B and the 14-3-3{zeta}-complex in cells treated with epidermal growth factor (EGF). We also demonstrated that preventing the association of this 14-3-3{zeta}-complex to PTP1B deterred oxidation and inactivation of PTP1B following EGF receptor (EGFR) activation and generation of ROS. Treating cells with our PPI inhibitor decreased EGFR phosphorylation on PTP1B-specific sites. Furthermore, treating EGFR-driven epidermal cancer cells with our PPI inhibitor also significantly inhibited colony formation and cell viability, consitent with increased activation of PTP1B. These data highlight the ability of PTP1B to downregulate critical signaling pathways in cancer when activated using peptide drugs such as our protein-protein interaction inhibitor. We anticipate that preventing or destabilizing the reversible oxidation of other members of the protein tyrosine phosphatase superfamily using PPI inhibitors may offer a foundation for a broad therapeutic approach to rectify dysregulated signaling pathways in vivo. Significance StatementLimited understanding of redox mechanisms regulating PTP catalytic activity is a major knowledge gap that has hampered our efforts to develop activation strategies. In its reversibly oxidized and inactivated form, conformational changes of PTP1B influence its association with regulatory proteins. We demonstrate that designing a cell-permeable peptide based on a loop of PTP1B that becomes exposed during oxidation can block its interaction with the 14-3-3{zeta}-multiprotein complex and activate the phosphatase. Moreover, activating PTP1B using our protein-protein interaction inhibitor peptide decreases the phosphorylation of its substrate EGFR and decreases the effectiveness of cancer cells to form colonies. This study provides important insights into the therapeutic potential of protein-protein interaction inhibitors that regulate the redox cycle of PTPs to reestablish physiological signaling.

biochemistry↗

bioRxiv2025

PTPRJ-Targeting Peptide Agonist Induces Broad Cellular Signaling Perturbations and DNA Damage in Lung Cancer Cells

Receptor protein tyrosine phosphatases (RPTPs) are key regulators of cell signaling. However, their study and therapeutic targeting have been limited by the lack of known natural ligands or selective agonists, as well as an incomplete understanding of their structure-function relationships. Nonetheless, receptor homodimerization has been shown to suppress RPTP catalytic activity by restricting substrate access, offering a promising strategy for examining and modulating their function. Our previous work on PTPRJ, a member of the RPTP family, showed that its transmembrane domain regulates homodimerization, thereby controlling access to receptor tyrosine kinase (RTK) substrates and their phosphorylation levels. We also developed peptides that disrupt this dimerization, thereby inhibiting RTK phosphorylation and reducing cancer cell migration. These peptides were then engineered for selective, pH-sensitive insertion into the acidic tumor microenvironment to enhance efficacy while limiting off-target effects. Yet how broadly PTPRJ activation reshapes the phosphotyrosine landscape and whether those changes yield coherent cellular phenotypes remains unclear. In this study, we employed tyrosine phosphoproteomics, immunoblotting, immunofluorescence, and functional assays to assess the global impact of our lead peptide candidate, Hybrid 7, in A549 lung cancer cells that endogenously express PTPRJ. We find that Hybrid 7 decreases EGFR phosphorylation and selectively reduces phosphorylation across additional RTKs and motility adaptors, producing strong inhibition of EGF-driven migration and reduced proliferation. Hybrid 7 also elevates reactive oxygen species and DNA damage, and enforces CDK1-dependent G2/M arrest, indicating a primarily cytostatic, checkpoint-mediated response. These findings highlight the potential of RPTP-targeting peptides as valuable tools for dissecting RPTP function and as possible therapeutic agents capable of modulating key oncogenic pathways and inhibiting cancer progression.

biochemistry↗

bioRxiv2023

Modification of the antibiotic, colistin, with dextrin causes enhanced cytotoxicity and triggers apoptosis in myeloid leukemia

Acute myeloid leukemia (AML) remains difficult to treat due to its heterogeneity in molecular landscape, epigenetics and cell signaling alterations. Precision medicine is a major goal in AML therapy towards developing agents that can be used to treat patients with different subtypes in combination with current chemotherapies. We have previously developed dextrin-colistin conjugates to combat the rise in multi-drug resistant bacterial infections and overcome dose-limiting nephrotoxicity. Recent evidence of colistins anticancer activity, mediated through inhibition of intracellular lysine-specific histone demethylase 1 (LSD1/KDM1A), suggests that dextrin-colistin conjugates could be used to treat cancer cells, including AML. This study aimed to evaluate whether dextrin conjugation (which reduces in vivo toxicity and prolongs plasma half-life) could enhance colistins cytotoxic effects in myeloid leukemia cell lines and compare the intracellular uptake and localization of the free and conjugated antibiotic. Our results identified a conjugate (containing 8,000 g/mol dextrin with 1 mol% succinoylation) that caused significantly increased toxicity in myeloid leukemia cells, compared to free colistin. Dextrin conjugation altered the mechanism of cell death by colistin, from necrosis to caspase 3/7-dependent apoptosis. In contrast, conjugation via a reversible ester linker, instead of an amide, had no effect on the mechanism of the colistin-induced cell death. Live cell confocal microscopy of fluorescently-labelled compounds showed both free and dextrin-conjugated colistin were endocytosed and co-localized in lysosomes and increasing the degree of modification by succinoylation of dextrin significantly reduced colistin internalization. Whilst clinical translation of dextrin-colistin conjugates for the treatment of AML is unlikely due to the potential to promote AMR and the relatively high colistin concentrations required for anticancer activity, the ability to potentiate the effectiveness of an anticancer drug by polymer conjugation, while reducing side effects and improving biodistribution of the drug, is very attractive, and this approach warrants further investigation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=71 SRC="FIGDIR/small/565276v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@1cb7aaorg.highwire.dtl.DTLVardef@15e3574org.highwire.dtl.DTLVardef@7577aorg.highwire.dtl.DTLVardef@eb4_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2023

Dextrin conjugation to colistin inhibits its toxicity, cellular uptake and acute kidney injury in vivo.

The acute kidney injury (AKI) and dose-limiting nephrotoxicity, which occurs in 20-60% of patients following systemic administration of colistin, represents a challenge in the effective treatment of multi-drug resistant gram-negative infections. To reduce clinical toxicity of colistin and improve targeting to infected /inflamed tissues, we previously developed dextrin-colistin conjugates, whereby colistin is designed to be released by amylase-triggered degradation of dextrin in infected and inflamed tissues, after passive targeting by the enhanced permeability and retention effect. Whilst it was evident in vitro that polymer conjugation can reduce toxicity and prolong plasma half-life, without significant reduction in antimicrobial activity of colistin, it was unclear how dextrin conjugation would alter cellular uptake and localisation of colistin in renal tubular cells in vivo. We discovered that dextrin conjugation effectively reduced colistins toxicity towards human kidney proximal tubular epithelial cells (HK-2) in vitro, which was mirrored by significantly less cellular uptake of Oregon Green (OG)-labelled dextrin-colistin conjugate, when compared to colistin. Using live-cell confocal imaging, we revealed localisation of both, free and dextrin-bound colistin in endolysosome compartments of HK-2 and NRK-52E cells. Using a murine AKI model, we demonstrated dextrin-colistin conjugation dramatically diminishes both proximal tubular injury and renal accumulation of colistin. These findings reveal new insight into the mechanism by which dextrin conjugation can overcome colistins renal toxicity and show the potential of polymer conjugation to improve the side effect profile of nephrotoxic drugs. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=126 SRC="FIGDIR/small/565265v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@1ec6ac8org.highwire.dtl.DTLVardef@56a2b1org.highwire.dtl.DTLVardef@1d347fborg.highwire.dtl.DTLVardef@1ab7da_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2022

COVID-19 Neuropathology: evidence for SARS-CoV-2 invasion of Human Brainstem Nuclei

Neurological manifestations are common in COVID-19, the disease caused by SARS-CoV-2. Despite reports of SARS-CoV-2 detection in the brain and cerebrospinal fluid of COVID-19 patients, its still unclear whether the virus can infect the central nervous system, and which neuropathological alterations can be ascribed to viral tropism, rather than immune-mediated mechanisms. Here, we assess neuropathological alterations in 24 COVID-19 patients and 18 matched controls who died due to pneumonia / respiratory failure. Aside from a wide spectrum of neuropathological alterations, SARS-CoV-2-immunoreactive neurons were detected in specific brainstem nuclei of 5 COVID-19 subjects. Viral RNA was also detected by real-time RT-PCR. Quantification of reactive microglia revealed an anatomically segregated pattern of inflammation within affected brainstem regions, and was higher when compared to controls. While the results of this study support the neuroinvasive potential of SARS-CoV-2, the role of SARS-CoV-2 neurotropism in COVID-19 and its long-term sequelae require further investigation.

neuroscience↗