Biology subjects

Reigan, P.

Publications and source records attributed to Reigan, P..

4 recordsLinked to original sources

bioRxiv2026

Metabolite mimicry identifies butyrate analogs with select protective functions in the intestinal mucosa

Microbial-derived short-chain fatty acids regulate a variety of pathways in the healthy colonic mucosa. In particular, butyrate serves as the primary energy source for colonocytes and regulates gene transcription by stabilizing the transcription factor hypoxia-inducible-factors (HIF) and functioning as a histone deacetylase (HDAC) inhibitor. A limitation of butyrate as a therapeutic is its rapid metabolism in differentiated colonocytes. Furthermore, intestinal stem cells (ISCs) respond differently to butyrate, preferentially using glucose for energy procurement. To address these limitations, we explored metabolite-mimicry to discover compounds with potent or selective biological responses within the butyrate pathway(s). We discovered an analog, 3-chlorobutyrate (3-Cl BA), that significantly enhances epithelial barrier formation and wound healing in vitro. Mechanistically, we revealed that 3-Cl BA is a potent HDAC inhibitor. Furthermore, unlike butyrate, 3-Cl BA does not stabilize HIF and it is not used as metabolic fuel. In vivo studies in a DSS-colitis model revealed that contrary to butyrate, 3-Cl BA is protective. Studies in stem-like colonoids demonstrated that only butyrate inhibits ISC proliferation and differentiation. Furthermore, it was recently reported that HIF stabilization inhibits ISCs activity. Given the fact that butyrate but not 3-Cl BA stabilizes HIF, we surmised that 3-Cl BA would circumvent these detrimental functional consequences. We demonstrate here that pharmacologic HIF stabilization inhibits colonoid differentiation and that genetic loss of HIF significantly promotes ISC differentiation. This study reveals a promising butyrate analog protective in colitis and demonstrates the advantages of metabolite-mimicry to dissect selective biological functions from major metabolites in the gut. Significance statementButyrate is a well-studied microbial short-chain fatty acid that regulates a number of mucosal pathways and is paramount in maintaining intestinal integrity. In health, it is a major source of energy for colonocytes and regulates gene transcription. The role of butyrate in disease is still controversial and not well understood. When butyrate is not metabolized or well-utilized (e.g. disease), it accumulates in intestinal stem cells leading to reduced cell proliferation and differentiation, thereby hampering intestinal barrier recovery. In this study, we describe a butyrate analog that enhances epithelial barrier formation and wound healing. Furthermore, as opposed to native butyrate, this butyrate analog is protective in a colitis mouse model and does not exhibit detrimental influences on intestinal stem cells. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/697087v1_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@1dd0f0borg.highwire.dtl.DTLVardef@6d27forg.highwire.dtl.DTLVardef@1e5d07corg.highwire.dtl.DTLVardef@dab74f_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO Microbially derived butyrate plays a key role in intestinal homeostasis. It is the primary source of energy for colonocytes, contributing to a metabolic and oxygen gradient as it is metabolized by differentiated cells along the intestinal crypt. Through the regulation of transcription factors such as HIF and the inhibition of HDAC, it regulates barrier formation and wound healing promoting a strong tight junction profile. Furthermore, well oxygenated ISCs at the bottom of the crypt are unaccustomed to the effects of butyrate, including HIF stabilization (left). In disease, loss of intestinal architecture leads to a disrupted metabolic/oxygen gradient where butyrate accumulates in stem cells leading to decreased proliferation, differentiation, and increases in apoptosis. 3-Cl BA selectively acts as an HDACi and does not stabilize HIF, exhibiting no significant detrimental effects on ISCs (right). Created in BioRender. Ornelas, A. (2026) https://BioRender.com/x9cy8mw C_FIG

molecular biology↗

bioRxiv2024

BRAF V600 and ErbB inhibitors directly activate GCN2 in an off-target manner to limit cancer cell proliferation

Targeted kinase inhibitors are well known for their promiscuity and off-target effects. Herein, we define an off-target effect in which several clinical BRAFV600 inhibitors, including the widely used dabrafenib and encorafenib, interact directly with GCN2 to activate the Integrated Stress Response and ATF4. Blocking this off-target effect by co-drugging with a GCN2 inhibitor in A375 melanoma cells causes enhancement rather than suppression of cancer cell outgrowth, suggesting that the off-target activation of GCN2 is detrimental to these cells. This result is mirrored in PC9 lung cancer cells treated with erlotinib, an EGFR inhibitor, that shares the same off-target activation of GCN2. Using an in silico kinase inhibitor screen, we identified dozens of FDA-approved drugs that appear to share this off-target activation of GCN2 and ATF4. Thus, GCN2 activation may modulate the therapeutic efficacy of some kinase inhibitors, depending on the cancer context.

cancer 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↗