Biology subjects

Kaber, G.

Publications and source records attributed to Kaber, G..

9 recordsLinked to original sources

bioRxiv2023

Inhibition of hyaluronan synthesis prevents β-cell loss in obesity-associated type 2 diabetes

Pancreatic {beta}-cell dysfunction and death are central to the pathogenesis of type 2 diabetes (T2D). We have identified a novel role for the inflammatory extracellular matrix polymer hyaluronan (HA) in this pathophysiology. Low levels of HA are present in healthy pancreatic islets. However, HA substantially accumulates in cadaveric islets of human T2D and islets of the db/db mouse model of T2D in response to hyperglycemia. Treatment with 4-methylumbelliferone (4-MU), an inhibitor of HA synthesis, or the deletion of the major HA receptor CD44, preserve glycemic control and insulin levels in db/db mice despite ongoing weight gain, indicating a critical role for this pathway in T2D pathogenesis. 4-MU treatment and the deletion of CD44 likewise preserve glycemic control in other settings of {beta}-cell injury including streptozotocin treatment and islet transplantation. Mechanistically, we find that 4-MU increases the expression of the apoptosis inhibitor survivin, a downstream transcriptional target of CD44 dependent on HA/CD44 signaling, on {beta}-cells such that caspase 3 activation does not result in {beta}-cell apoptosis. These data indicate a role for HA accumulation in diabetes pathogenesis and suggest that it may be a viable target to ameliorate {beta}-cell loss in T2D. These data are particularly exciting, because 4-MU is already an approved drug (also known as hymecromone), which could accelerate translation of these findings to clinical studies.

immunology↗

bioRxiv2023

FOXP3+ regulatory T cells use heparanase to access IL-2 bound to ECM in inflamed tissues

FOXP3+ regulatory T cells (Treg) depend on exogenous IL-2 for their survival and function, but circulating levels of IL-2 are low, making it unclear how Treg access this critical resource in vivo. Here, we show that Treg use heparanase (HPSE) to access IL-2 sequestered by heparan sulfate (HS) within the extracellular matrix (ECM) of inflamed central nervous system tissue. HPSE expression distinguishes human and murine Treg from conventional T cells and is regulated by the availability of IL-2. HPSE-/- Treg have impaired stability and function in vivo, including the experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis. Conversely, endowing Treg with HPSE enhances their ability to access HS-sequestered IL-2 and their tolerogenic function in vivo. Together, these data identify novel roles for HPSE and the ECM in immune tolerance, providing new avenues for improving Treg-based therapy of autoimmunity. One-Sentence SummaryRegulatory T cells use heparanase to strip IL-2 bound to extracellular matrix within inflamed tissues, thereby supporting their homeostasis and function.

immunology↗

bioRxiv2022

Pf Bacteriophage Inhibits Neutrophil Migration in the Lung

Bacteriophages are abundant in the human body, including at sites of infection. We report that Pf4 phage, a filamentous bacteriophage produced by Pseudomonas aeruginosa, dampens inflammatory responses in response to either P. aeruginosa airway infection in a mouse model of acute pneumonia or bacterial endotoxin treatment. Pf4 triggers TLR3-dependent type I interferon production and antagonize production of anti-bacterial cytokines and chemokines. In particular, Pf4 phages inhibit CXCL5, preventing efficient neutrophil chemotaxis in response to endotoxin. These results suggest that Pf4 phages alter innate immunity to bacteria potentially dampening inflammation and neutrophil migration at sites of bacterial colonization or infection.

immunology↗

bioRxiv2022

A filamentous phage triggers antiviral responses in cystic fibrosis basal airway epithelial cells

Basal airway epithelial cells are a multipotent stem cell population which gives rise to several airway cell types. Basal cells are known to be critical to airway epithelium homeostasis and repair, and altered basal cell phenotypes have been reported in cystic fibrosis and idiopathic pulmonary fibrosis. However, very little is known about how basal cells respond to stimuli in the cystic fibrosis airway environment. Cystic fibrosis patients experience chronic infection with Pseudomonas aeruginosa and contain both high quantities of lipopolysaccharide (LPS) as well as the filamentous bacteriophage Pf produced by biofilm-state P. aeruginosa in the airway. In this study, we sought to investigate the transcriptional responses of human basal cells from both healthy controls and patients with cystic fibrosis to LPS and Pf phage. Basal cells from wildtype and cystic fibrosis donors were cultured in vitro and exposed to LPS and/or Pf phage, followed by single-cell sequencing on the 10x platform. We report that basal cells show strong antiviral responses and neutrophil chemokine production in response to Pf phage. We validate these findings in additional donors by qRT-PCR and show that Pf phage is internalized by basal cells. We also show that Pf decreases basal cell migration and proliferation. We demonstrate that Pf phage, a bacteria-infecting virus which does not replicate in mammalian cells, is taken up by basal cells and activates immune responses. Further studies are needed to determine the impact of this antiviral response to bacterial clearance. Author SummaryWhen we experience a lung infection or injury, the stem cells of the airway--called basal epithelial cells--are crucial for healing the affected tissue. Basal cells proliferate and migrate to close gaps in the epithelium and replace injured and dead cells. We are also learning that basal cells can directly contribute to the immune response against lung pathogens, although little is understood about how basal cells sense viruses and bacteria, and what molecules they secrete in response. In our work, we sought to investigate the role that basal cells play in the course of an infection with the common human pathogen Pseudomonas aeruginosa. We stimulated basal cells with lipopolysaccharide (LPS), a potent immunogen produced by Pseudomonas, as well as the Pseudomonas-infecting virus Pf4. We have previously shown that Pf4, which is produced in high amounts by lung-infecting Pseudomonas, affects the immune response to this bacterium. In our work here, we show that Pf4 is recognized as a virus by basal cells and changes the transcriptional response to LPS, derailing the antibacterial immune response to Pseudomonas. These findings raise the question of whether other bacteria-infecting viruses alter immune responses, and how these viruses interact with other airway cells.

cell biology↗

bioRxiv2022

The pharmacokinetics and pharmacodynamics of 4-methylumbelliferone and its glucuronide metabolite in mice

Hyaluronan (HA) is an extracellular matrix glycosaminoglycan, with important roles in chronic inflammation, cancer and autoimmunity. 4-methylumbelliferone (4-MU), a small molecule inhibitor of HA synthases, is widely used to study HAs interactions with the surrounding tissues and the immune cells. There is substantial experimental and therapeutic interest in using oral 4-MU to inhibit HA synthesis, but pharmacokinetic and pharmacodynamic data on treatment routes have been lacking. Moreover, it recently became clear that the main metabolite of 4-MU, 4-methlyumbelliferyl glucuronide (4-MUG), is bioactive. We therefore sought to define the pharmacokinetics and pharmacodynamics of 4-MU and its active metabolite 4-MUG in mice. Single dose mouse studies showed that 4-MU administered intravenously (i.v.) resulted in 100-fold higher 4-MU exposure compared to oral (p.o.) administration. The 4-MU ratio AUC i.v./AUC p.o. was 96/1. 4-MUG exposures were much higher than 4-MU exposures after both 4-MU i.v. and p.o. administration, but only small differences in 4-MUG exposure were seen after 4-MU i.v. versus p.o. administration. The 4-MUG metabolite was also administered as a single dose both i.v. and p.o. and showed a 25.9% bioavailability. Compared to 4-MUG p.o. dosing, 1.14 higher 4-MUG exposures were seen after 4-MU p.o. dosing. 4-MU exposure after 4-MUG p.o. administration was minimal but similar to 4-MU exposure after 4-MU p.o. administration. In mice treated for several weeks with 4-MU in chow, the 4-MU concentration immediately drops after treatment was stopped, whereas the 4-MUG concentration showed a peak 1 hour after treatment stop. In a build-up study, 4-MU and 4-MUG treatment in mice lead to a plateau of 4-MU concentration starting at 4 days post treatment start. These 4-MU and 4-MUG concentration findings in vivo will inform future clinical studies and experimental work with 4-MU.

pharmacology and toxicology↗

bioRxiv2022

The circulating phageome reflects bacterial infections

Bacteriophage, viruses that infect bacteria, are abundant in the human body but the relationship between the phageome and bacterial population dynamics is unclear. Because bacteriophage are often highly specific to bacterial host strains and species, we asked whether bacteriophage present in cell-free DNA (cfDNA) reflect bacterial infections in sepsis. To address this, we generated a workflow for identifying and interpreting bacteriophage sequences in cfDNA and a bacteriophage characteristic dictionary. In two independent cohorts of infected patients and asymptomatic controls, we demonstrate that all individuals, septic and healthy, have a circulating phageome. Moreover, infection associates with overrepresentation of pathogen-specific phage, allowing for the study of bacterial pathogens. We further show that phage can identify pathovariant Escherichia coli infections and distinguish between closely-related pathogenic bacterial species such as Staphylococcus aureus and frequent contaminants such as coagulase-negative Staphylococcus. Phage DNA may have utility in studying bacteriophage ecology in infection.

microbiology↗

bioRxiv2020

Hyaluronan Synthesis Inhibition Impairs Antigen Presentation and Delays Transplantation Rejection

A coat of pericellular hyaluronan surrounds mature dendritic cells (DC) and contributes to cell-cell interactions. We asked whether 4-methylumbelliferone (4MU), an oral inhibitor of HA synthesis, could inhibit antigen presentation. We find that 4MU treatment reduces pericellular hyaluronan, destabilizes interactions between DC and T-cells, and prevents T-cell proliferation in vitro and in vivo. These effects were observed only when 4MU was added prior to initial antigen presentation but not later, consistent with 4MU-mediated inhibition of de novo antigenic responses. Building on these findings, we find that 4MU delays rejection of allogeneic pancreatic islet transplant and allogeneic cardiac transplants in mice and suppresses allogeneic T-cell activation in human mixed lymphocyte reactions. We conclude that 4MU, an approved drug, may have benefit as an adjunctive agent to delay transplantation rejection.

immunology↗

bioRxiv2020

Sustained Release of IL-2 Using an Injectable Hydrogel Prevents Autoimmune Diabetes

Interleukin 2 (IL-2) is a promising therapy for autoimmune type 1 diabetes (T1D), but the short half-life in vivo (less than 6 minutes) limits effective tissue exposure to IL-2. Tissue exposure is required for the tolerogenic effects of IL-2. We have developed an injectable hydrogel that incorporates heparin polymers to enable the sustained release of IL-2. This platform uses clinical grade and commercially available materials, including collagen, hyaluronan, and heparin, to deliver IL-2 by slowly degrading and releasing IL-2 over a two-week period in vivo. We find that heparin potentiates the activity of IL-2 and IL-2-mediated expansion of Foxp3+ regulatory T cell (Treg). Hydrogel-mediated IL-2 release showed a reduction of CD4+ and CD8+ T cells and an increase of FoxP3+ Treg in the lymph nodes of injected mice. Moreover, in the Non-Obese Diabetic (NOD) mouse model of T1D once-weekly administration of IL-2 hydrogels prevented diabetes onset as efficiently as 3x weekly repeated injections of soluble IL-2. Together these data suggest that heparin-containing hydrogels may have benefit in delivering low-dose IL-2 and promoting immune tolerance in autoimmune diabetes.

immunology↗

bioRxiv2020

Filamentous Bacteriophage Delay Healing of Pseudomonas-Infected Wounds

We have identified a novel role for filamentous bacteriophage in the delayed healing associated with chronic Pseudomonas aeruginosa (Pa) wound infections. Pf phage delays wound re-epithelialization in the absence of live Pa, indicative that Pf effects on wound healing are independent of Pa pathogenesis. Pf phage directly inhibits autocrine signaling of CXCL1 (KC) to impede keratinocyte migration and wound re-epithelization. In agreement with these studies, a prospective cohort study of 36 human patients with chronic Pa wound infections revealed that wounds infected with Pf positive strains of Pa took longer to heal and were more likely to increase in size compared to wounds infected with Pf negative strains. Together, these data implicate Pf phage in the delayed wound healing associated with Pa infection through direct manipulation of mammalian target cells. We propose that Pf phage may have potential as a biomarker and therapeutic target in delayed wound healing.

microbiology↗