Biology subjects

Tjalkens, R. B.

Publications and source records attributed to Tjalkens, R. B..

6 recordsLinked to original sources

bioRxiv2024

Sex specific effects of environmental toxin-derived alpha synuclein on enteric neuronal-epithelial interactions

BackgroundParkinsons Disease (PD) is a neurodegenerative disorder with prodromal gastrointestinal (GI) issues often emerging decades before motor symptoms. Pathologically, PD can be driven by accumulation of misfolded alpha synuclein (aSyn) protein in the brain and periphery, including the GI tract. Disease epidemiology differs by sex, with men twice as likely to develop PD. Women, however, experience faster disease progression, higher mortality, and more severe GI symptoms. Gut calcitonin gene related peptide (CGRP) is a key regulator of intestinal contractions and visceral pain. The current study tests the hypothesis that sex differences in GI symptomology in PD are the result of aSyn aggregation altering enteric CGRP signaling pathways. MethodsTo facilitate peripheral aSyn aggregation, the pesticide rotenone was administered intraperitoneally once daily for two weeks to male and female mice. Mice were sacrificed two weeks after the last rotenone injection and immunohistochemistry was performed on sections of proximal colon. Key ResultsLevels of aSyn were heightened in myenteric plexus neurons and a subset of neurons immunoreactive to CGRP in rotenone treated mice. Female mice exhibited 153% more myenteric aSyn, 26% more apical CGRP immunoreactivity, and 66.7% more aSyn in apical CGRP+ fibers after rotenone when compared to males. Goblet cell numbers were diminished but the individual cells were larger in the apical regions of crypts in the colons of rotenone treated mice. ConclusionsThis study used a mouse model of PD to uncover sex specific alterations in enteric neuronal and epithelial populations, underscoring the importance of considering sex as a biological variable while investigating prodromal GI symptoms. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=143 HEIGHT=200 SRC="FIGDIR/small/625701v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@19a6dforg.highwire.dtl.DTLVardef@1a9324org.highwire.dtl.DTLVardef@b253d4org.highwire.dtl.DTLVardef@19d89cf_HPS_FORMAT_FIGEXP M_FIG C_FIG KEY POINTSO_LIMouse model of Parkinsons Disease (PD) was used to investigate sex specific impact of enteric alpha synuclein (aSyn) on colonic goblet cells and CGRP+ neurons and fibers. C_LIO_LISex specific alterations in intestinal neuronal and epithelial signaling pathways in response to aSyn provides insight into sex differences in PD etiology and prodromal gastrointestinal symptoms. C_LI

physiology↗

bioRxiv2024

Microglia-specific NF-κB signaling is a critical regulator of prion-induced glial inflammation and neuronal loss

Prion diseases are a group of rare and fatal neurodegenerative diseases caused by the cellular prion protein, PrPC, misfolding into the infectious form, PrPSc, which forms aggregates in the brain. This leads to activation of glial cells, neuroinflammation, and irreversible neuronal loss, however, the role of glial cells in prion disease pathogenesis and neurotoxicity is poorly understood. Microglia can phagocytose PrPSc, leading to the release of inflammatory signaling molecules, which subsequently induce astrocyte reactivity. Animal models show highly upregulated inflammatory molecules that are a product of the Nuclear Factor-kappa B (NF-{kappa}B) signaling pathway, suggesting that this is a key regulator of inflammation in the prion-infected brain. The activation of the I{kappa}B kinase complex (IKK) by cellular stress signals is critical for NF-{kappa}B-induced transcription of a variety of genes, including pro-inflammatory cytokines and chemokines, and regulators of protein homeostasis and cell survival. However, the contribution of microglial IKK and NF-{kappa}B signaling in the prion-infected brain has not been evaluated. Here, we characterize a primary mixed glial cell model containing wild-type (WT) astrocytes and IKK knock-out (KO) microglia. We show that, when exposed to prion-infected brain homogenates, NF-{kappa}B-associated genes are significantly downregulated in mixed glial cultures containing IKK KO microglia. Mice with IKK KO microglia show rapid disease progression when intracranially infected with prions, including an increase in microglia and reactive astrocytes, and accelerated loss of hippocampal neurons and associated behavioral deficits. These animals display clinical signs of prion disease early and have a 22% shorter life expectancy compared to infected wild-type mice. Intriguingly, PrPSc accumulation was significantly lower in the brains of infected animals with IKK KO microglia compared to age-matched controls, suggesting that accelerated disease is independent of PrPSc accumulation, highlighting a glial-specific pathology. Conversely, primary mixed glia with IKK KO microglia have significantly more PrPSc accumulation when exposed to infected brain homogenates. Together, these findings present a critical role in NF-{kappa}B signaling from microglia in host protection suggesting that microglial IKK may be involved in sufficient clearance of prions.

molecular biology↗

bioRxiv2024

Neuroprotective efficacy of the glucocorticoid receptor modulator PT150 in the rotenone mouse model of Parkinsons disease

Parkinsons disease (PD) is the most common neurodegenerative movement disorder worldwide. Current treatments for PD largely center around dopamine replacement therapies and fail to prevent the progression of pathology, underscoring the need for neuroprotective interventions. Approaches that target neuroinflammation, which occurs prior to dopaminergic neuron (DAn) loss in the substantia nigra (SN), represent a promising therapeutic strategy. The glucocorticoid receptor (GR) has been implicated in the neuropathology of PD and modulates numerous neuroinflammatory signaling pathways in the brain. Therefore, we investigated the neuroprotective effects of the novel GR modulator, PT150, in the rotenone mouse model of PD, postulating that inhibition of glial inflammation would protect DAn and reduce accumulation of neurotoxic misfolded -synuclein protein. C57Bl/6 mice were exposed to 2.5 mg/kg/day rotenone by intraperitoneal injection for 14 days, immediately followed by oral treatment with 30 mg/kg/day or 100 mg/kg/day PT150 in the 14-day post-lesioning incubation period, during which the majority of DAn loss and -synuclein (-syn) accumulation occurs. Our results indicate that treatment with PT150 reduced both loss of DAn and microgliosis in the nigrostriatal pathway. Although morphologic features of astrogliosis were not attenuated, PT150 treatment promoted potentially neuroprotective activity in these cells, including increased phagocytosis of hyperphosphorylated -syn. Ultimately, PT150 treatment reduced the loss of DAn cell bodies in the SN, but not the striatum, and prohibited intra-neuronal accumulation of -syn. Together, these data indicate that PT150 effectively reduced SN pathology in the rotenone mouse model of PD.

neuroscience↗

bioRxiv2021

A novel glucocorticoid and androgen receptor modulator reduces viral entry and innate immune inflammatory responses in the Syrian Hamster model of SARS-CoV-2

Since its initial discovery in late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of COVID19, has spread worldwide and despite significant research efforts, treatment options remain limited. Replication of SARS-CoV-2 in lung is associated with marked infiltration of macrophages and activation of innate immune inflammatory responses triggered, in part, by heightened production of interleukin-6 (IL-6) that recruits lymphocytes to the site of infection that amplify tissue injury. Antagonists of the glucocorticoid and androgen receptors have shown promise in experimental models of COVID19 and in clinical studies, because cell surface proteins required for viral entry, angiotensin converting enzyme 2 (ACE2) and the transmembrane serine protease 2 (TMPRSS2), are transcriptionally regulated by these receptors. We therefore postulated that the glucocorticoid (GR) and androgen receptor (AR) antagonist, PT150, would reduce infectivity of SARS-CoV-2 and prevent inflammatory lung injury in the Syrian golden hamster model of COVID19. Animals were infected intranasally with 2.5 x 104 TCID50/ml equivalents of SARS-CoV-2 (strain 2019-nCoV/USA-WA1/ 2020) and PT150 was administered by oral gavage at 30 and 100 mg/Kg/day for a total of 7 days. Animals were then examined at days 3, 5 and 7 post-infection (DPI) for lung histopathology, viral load and production of proteins regulating the initiation and progression of SARS-CoV-2 infection. Results of these studies indicated that oral administration of PT150 decreased replication of SARS-CoV-2 in lung, as well as expression of ACE2 and TMPRSS2 protein. Hypercellularity and inflammatory cell infiltration driven by macrophage responses were dramatically decreased in PT150-treated animals, as was tissue damage and expression of IL-6. Molecular modeling suggested that PT150 binds to the co-activator interface of the ligand binding domain of both AR and GR and thereby acts as an allosteric modulator and transcriptional repressor of these receptors. Phylogenetic analysis of AR and GR across multiple species permissive to SARS-CoV-2 infection revealed a high degree of sequence identity maintained across species, including human, suggesting that the mechanism of action and therapeutic efficacy observed in Syrian hamsters would likely be predictive of positive outcomes in patients. PT150 is therefore a strong candidate for further clinical development for the treatment of COVID19 across variants of SARS-CoV-2.

immunology↗

bioRxiv2020

A potent SARS-CoV-2 neutralizing human monoclonal antibody that reduces viral burden and disease severity in Syrian hamsters

The emergence of COVID-19 has led to a pandemic that has caused millions of cases of disease, variable morbidity and hundreds of thousands of deaths. Currently, only remdesivir and dexamethasone have demonstrated limited efficacy, only slightly reducing disease burden, thus novel approaches for clinical management of COVID-19 are needed. We identified a panel of human monoclonal antibody clones from a yeast display library with specificity to the SARS-CoV-2 spike protein receptor binding domain that neutralized the virus in vitro. Administration of the lead antibody clone to Syrian hamsters challenged with SARS-CoV-2 significantly reduced viral load and histopathology score in the lungs. Moreover, the antibody interrupted monocyte infiltration into the lungs, which may have contributed to the reduction of disease severity by limiting immunopathological exacerbation. The use of this antibody could provide an important therapy for treatment of COVID-19 patients.

microbiology↗

bioRxiv2020

SARS-CoV-2 infection, neuropathogenesis and transmission among deer mice: Implications for reverse zoonosis to New World rodents

Coronavirus disease-19 (COVID-19) emerged in November, 2019 in China and rapidly became pandemic. As with other coronaviruses, a preponderance of evidence suggests the virus originated in horseshoe bats (Rhinolophus spp.) and likely underwent a recombination event in an intermediate host prior to entry into human populations. A significant concern is that SARS-CoV-2 could become established in secondary reservoir hosts outside of Asia. To assess this potential, we challenged deer mice (Peromyscus maniculatus) with SARS-CoV-2 and found robust virus replication in the upper respiratory tract, lungs and intestines, with detectable viral RNA for up to 21 days in oral swabs and 14 days in lungs. Virus entry into the brain also occurred, likely via gustatory-olfactory-trigeminal pathway with eventual compromise to the blood brain barrier. Despite this, no conspicuous signs of disease were observed and no deer mice succumbed to infection. Expression of several innate immune response genes were elevated in the lungs, notably IFN, Cxcl10, Oas2, Tbk1 and Pycard. Elevated CD4 and CD8{beta} expression in the lungs was concomitant with Tbx21, IFN{gamma} and IL-21 expression, suggesting a type I inflammatory immune response. Contact transmission occurred from infected to naive deer mice through two passages, showing sustained natural transmission. In the second deer mouse passage, an insertion of 4 amino acids occurred to fixation in the N-terminal domain of the spike protein that is predicted to form a solvent-accessible loop. Subsequent examination of the source virus from BEI Resources indicated the mutation was present at very low levels, demonstrating potent purifying selection for the insert during in vivo passage. Collectively, this work has determined that deer mice are a suitable animal model for the study of SARS-CoV-2 pathogenesis, and that they have the potential to serve as secondary reservoir hosts that could lead to periodic outbreaks of COVID-19 in North America.

microbiology↗