Biology subjects

Frank, J. A.

Publications and source records attributed to Frank, J. A..

7 recordsLinked to original sources

bioRxiv2025

Luminal Vascular Dysfunction Drives Rapid Blood Brain Barrier Injury in Hyperglycemic Stroke: Key Roles for Luminal Glycocalyx and Complement

BackgroundAcute hyperglycemia affects approximately 40% of stroke patients and is associated with worse outcomes. The underlying mechanisms linking this metabolic stress to stroke-induced brain injury remains unclear, and effective therapies are lacking. MethodsIn a mouse model of acute hyperglycemic stroke, luminal disruption, blood-brain barrier (BBB) leakage, neurological deficit, motor function, and mortality were evaluated. Vascular luminal glycocalyx and complement activation were assessed by immunostaining, with glycocalyx loss confirmed by electron microscopy. Complement C3s causal role was tested using C3 knockout mice and site-targeted inhibition with CR2-Crry. To enhance translational relevance, post-mortem human stroke and control brains were immunostained to assess the association between endothelial glycocalyx loss and vascular complement activation. In a separate stroke patient cohort, soluble complement activation products were measured in pre-thrombectomy plasma, and their predictive value for modified Rankin Scale (mRS) outcomes evaluated using elastic net regression. ResultsHyperglycemic stroke mice exhibited accelerated and more severe BBB breakdown, greater functional deficits, and higher mortality than normoglycemic controls, mirroring clinical observations. Acute hyperglycemia triggered rapid vascular luminal injury characterized by loss of endothelial luminal glycocalyx, luminal IgM/IgG deposition, and vascular complement C3 activation, leading to BBB disruption. This vascular luminal injury was corroborated in human stroke brain tissue. These luminal changes persisted despite glucose normalization and were exacerbated by reperfusion, driving injury into the brain parenchyma. Genetic and pharmacological approaches confirmed vascular complement activation as a causal driver of severe BBB disruption and poor outcomes. Importantly, site-targeted pharmacological inhibition of complement after reperfusion preserved BBB integrity and improved outcomes, defining a time-specific, luminal-directed strategy as a promising adjunct to thrombectomy. Notably, soluble complement activation markers in pre-thrombectomy stroke plasma predicted clinical outcomes, highlighting their potential as pre-intervention markers for patient stratification and tailored therapy. ConclusionThis study reframes acute hyperglycemic stroke as a vascular luminal disorder, establishing a novel Metabolic-Complement-Vascular (MCV) axis linking metabolic stress to endothelial luminal glycocalyx loss, vascular complement activation, and BBB breakdown in both mice and humans. This new mechanistic understanding transforms the therapeutic landscape of hyperglycemic stroke, offering a potential time-defined, luminal-focused adjunct therapy alongside thrombectomy. Clinical PerspectiveO_ST_ABSWhat Is New?C_ST_ABS- This study reframes hyperglycemic stroke as an acute vascular luminal problem, marked by rapid loss of endothelial luminal glycocalyx and complement C3 activation at the vascular luminal surface. - The rapid luminal changes, identified in both rodent and human stroke brain tissues, establish a novel Metabolic-Complement-Vascular (MCV) axis linking metabolic stress to luminal damage, blood-brain barrier (BBB) breakdown, and injury progression into the brain parenchyma. - The first clinical evidence that pre-thrombectomy plasma complement activation markers independently predict stroke outcomes -- laying the foundation for risk stratification before reperfusion and precision adjunct therapies. What Are the Clinical Implications?- The rapidity and persistence of the MCV axis activation--even after glucose normalization--help explain the limited efficacy of insulin therapy, shifting the therapeutic focus from glycemic control to luminal-targeted interventions. - Identification of a narrow but actionable window following reperfusion where complement C3 inhibition preserves the BBB and limits injury progression to the parenchyma, offers a promising adjunct to thrombectomy in metabolically vulnerable stroke patients. - Targeting the vascular luminal surface reshapes the therapeutic landscape for hyperglycemic stroke by enabling systemic interventions--bypassing the challenge of BBB penetration, supporting rapid clinical translation using existing FDA-approved C3 inhibitors, and framing the endothelial glycocalyx as a promising area for therapeutic and diagnostic exploration in hyperglycemic stroke and broader cerebrovascular disease.

neuroscience↗

bioRxiv2025

The Photoswitchable Cannabinoid Azo-HU308 Enables Optical Control of Ca2+ Signaling in Pancreatic β-Cells via a Non CB2 TRPC Channel Mechanism

Background and PurposeCa2+ plays a critical role in regulating insulin secretion from pancreatic {beta}-cells, a process modulated by various cell surface receptors, including cannabinoid receptors (CBRs). However, our understanding of cannabinoid signaling in {beta}-cells is complicated by the intricate pharmacology of cannabinoid ligands and their inherent hydrophobicity, which hinders precise control of receptor activation. This study aims to investigate the effects of the light-activatable CB2 receptor agonist, azo-HU308, on {beta}-cell Ca2+ dynamics. Experimental ApproachWe employ fluorescent Ca2+ imaging in INS-1 832/13 (INS-1) {beta}-cells to measure Ca2+ transients induced by azo-HU308 and photoactivation with UV-A light. We then apply a pharmacological screen using a various CBR and TRP channel antagonists to determine the mechanism by which azo-HU308 enables optical control of {beta}-cell Ca2+ levels. Key ResultsWe observed that azo-HU308 triggers a robust increase in intracellular Ca2+ when isomerized to the cis-form with UV-A light. The effect was repeatable over multiple cycles of irradiation and gradually desensitized on each sequential UV-light pulse. A pharmacological screen determined that the Ca2+ increase was not due to CB2 receptor activation and Ca2+ release from intracellular stores, but rather influx of extracellular Ca2+ through TRPC channels. Conclusions and Implicationsazo-HU308 enables robust, repeatable stimulation of Ca2+ in INS-1 pancreatic {beta}-cells when triggered by UV-A light. This study presents a novel tool to optically control {beta}-cell Ca2+ dynamics, and sheds light on a new mechanism by which synthetic cannabinoids affect Ca2+ signaling through non-GPCR targets.

physiology↗

bioRxiv2024

Dissecting the role of CAR signaling architectures on T cell activation and persistence using pooled screening and single-cell sequencing

Chimeric antigen receptor (CAR) T cells represent a promising approach for cancer treatment, yet challenges remain such as limited efficacy due to a lack of T cell persistence. Given its critical role in promoting and modulating T cell responses, it is crucial to understand how alterations in the CAR signaling architecture influence T cell function. Here, we designed a combinatorial CAR signaling domain library and performed repeated antigen stimulation assays, pooled screening and single-cell sequencing to investigate T-cell responses triggered by different CAR architectures. Parallel comparisons of CAR variants, at early, middle and late timepoints during chronic antigen stimulation systematically assessed the impact of modifying signaling domains on T cell activation and persistence. Our data reveal the predominant influence of membrane-proximal domains in driving T cell phenotype. Additionally, we highlight the critical role of CD40 costimulation in promoting potent and persistent T cell responses, followed by CTLA4, which induces a long-term cytotoxic phenotype. This work deepens the understanding of CAR T cell biology and may be used to guide the future engineering of CAR T cell therapies.

synthetic biology↗

bioRxiv2021

Structural Diversity of Photoswitchable Sphingolipids for Optodynamic Control of Lipid Raft Microdomains

Sphingolipids are a structurally diverse class of lipids predominantly found in the plasma membrane of eukaryotic cells. These lipids can laterally segregate with other saturated lipids and cholesterol into lipid rafts; liquid-ordered (Lo) microdomains that act as organizing centers within biomembranes. Owing the vital role of sphingolipids for lipid segregation, controlling their lateral localization is of utmost significance. Hence, we made use of the light-induced trans-cis isomerization of azobenzene-modified acyl chains, to develop a set of photoswitchable sphingolipids, with different headgroups (hydroxyl, galactosyl, phosphocholine) and backbones (sphingosine, phytosphingosine, tetrahydropyran (THP)-blocked sphingosine), able to shuttle between liquid-ordered (Lo) and liquid-disordered (Ld) regions of model membranes upon irradiation with UV-A ({lambda} = 365 nm) and blue ({lambda} = 470 nm) light, respectively. Using combined high-speed atomic force microscopy, fluorescence microscopy, and force spectroscopy, we investigated how these active sphingolipids laterally remodel supported bilayers upon photo-isomerization, notably in terms of domain area changes, height mismatch, line tension, and membrane piercing. Hereby, we show that all sphingosine-(Azo-{beta}-Gal-Cer, Azo-SM, Azo-Cer) and phytosphingosine-based (Azo--Gal-PhCer, Azo-PhCer) photolipids behave similarly, promoting a reduction in Lo domain area when in the UV-adapted cis-isoform. In contrast, azo-sphingolipids having THP groups that block H-bonding at the sphingosine backbone (Azo-THP-SM, Azo-THP-Cer) induce an increase in the Lo domain area when in cis, accompanied by a major rise in height mismatch and line tension. These changes were fully reversible upon blue light-triggered isomerization of the various lipids back to trans, pinpointing the role of interfacial interactions for the formation of stable Lo lipid raft domains.

biophysics↗

bioRxiv2021

Pulsed Focal ultrasound as a non-invasive method to deliver exosomes in the brain/stroke

Exosomes, a component of extracellular vesicles are shown to carry important small RNAs, mRNAs, protein, and bioactive lipid from parent cells and are found in most biological fluids. Investigators have demonstrated the importance of mesenchymal stem cells (MSCs) derived exosomes in repairing stroke lesions. However, exosomes from endothelial progenitor cells (EPCs) have not been tested in any stroke model nor has there been an evaluation of whether these exosomes target/home to areas of pathology. Targeted delivery of IV administered exosomes has been a great challenge and a targeted delivery system is lacking to deliver naive (unmodified) exosomes from EPCs to the site of interest. Pulsed focused ultrasound (pFUS) is being used for therapeutic and experimental purposes. There has not been any report showing the use of pulsed low-intensity pFUS to deliver exosomes to the site of interest in models of stroke. In this proof of principle study, we have shown different parameters of pFUS to deliver exosomes in the intact and stroke brain with or without IV administration of nanobubbles. The study results showed that administration of nanobubbles is detrimental to the brain structures (micro bleeding and white matter destruction) at peak negative pressure (PNP) of >0.25 MPa, despite enhanced delivery of IV administered exosomes. However, without nanobubbles, pFUS PNP = 1 to 2 MPa enhances the delivery of exosomes in the stroke area without altering the brain structures.

neuroscience↗

bioRxiv2020

Antiviral activity of a human placental protein of retroviral origin

Endogenous retroviruses are abundant components of mammalian genomes descended from ancient germline infections. In several mammals, the envelope proteins encoded by these elements protect against exogenous viruses, but this activity has not been documented in human. We report that our genome harbors a large pool of envelope-derived sequences with the potential to restrict retroviral infection. To further test this, we characterize in detail the envelope-derived protein, Suppressyn. We found that Suppressyn is expressed in preimplantation embryos and developing placenta using its ancestral retroviral promoter. Restriction assays in cell culture show that Suppressyn, and its hominoid orthologs, can restrict infection by extant mammalian type D retroviruses. Our data support a generalizable model of retroviral envelope cooption for host immunity and genome defense. SummaryWe found that the human genome expresses a vast pool of envelope sequences of retroviral origin and provide proof of principle that such proteins can restrict zoonotic viruses.

molecular biology↗

bioRxiv2020

In vivo photopharmacology enabled by multifunctional fibers

To reversibly manipulate neural circuits with increased spatial and temporal control, photoswitchable ligands can add an optical switch to a target receptor or signaling cascade. This approach, termed photopharmacology, has been enabling to molecular neuroscience, however, its application to behavioral experiments has been impeded by a lack of integrated hardware capable of delivering both light and compounds to deep brain regions in moving subjects. Here, we devise a hybrid photochemical genetic approach to target neurons using a photoswitchable agonist of capsaicin receptor (TRPV1), red-AzCA-4. Using the thermal drawing process we created multifunctional fibers that can deliver viruses, photoswitchable ligands, and light to deep brain regions in awake, freely moving mice. We implanted our fibers into the ventral tegmental area (VTA), a midbrain hub of the mesolimbic pathway, and used them to deliver a transgene coding for TRPV1. This sensitized excitatory VTA neurons to red-AzCA-4, and allowed us to optically control conditioned place preference using a mammalian ion-channel, thus extending applications of photopharmacology to behavioral experiments. Applied to endogenous receptors, our approach may accelerate studies of molecular mechanisms underlying animal behavior.

neuroscience↗