Biology subjects

Seegren, P. V.

Publications and source records attributed to Seegren, P. V..

3 recordsLinked to original sources

bioRxiv2026

Endothelial TLR4 signaling drives tissue inflammation, Claudin-5 internalization, and vascular barrier breakdown in a mouse model of neonatal meningitis

Neonatal bacterial meningitis is a leading cause of infant morbidity and mortality, yet the molecular and cellular basis of the leptomeningeal response to infection remains poorly defined. Here, we study a mouse model of neonatal E. coli meningitis, combining conditional gene knockouts, leptomeningeal single-nucleus RNA sequencing, and endothelial cell culture to explore the role of Toll-like receptor 4 (TLR4) signaling in the host response to infection. Deletion of Tlr4 in non-myeloid cells dramatically reduced the inflammatory response in all leptomeningeal cell types and abrogated the infection- associated increase in vascular permeability. In a brain endothelial cell line (bEnd.3 cells), exposure to E. coli triggered NF-{kappa}B activation, selective internalization of Claudin- 5, and increased monolayer permeability, responses that were eliminated by Tlr4 knockout. RNA-seq showed that TLR4 controls an NF-{kappa}B-driven transcriptional program that orchestrates the endothelial response to E. coli. These findings reveal multiple TLR4-dependent host responses to neonatal Gram-negative bacterial meningitis.

pathology↗

bioRxiv2023

TRPM7-dependent electrical signals drive phagocytic clearance for effective anti-fungal defense

Sentinel phagocytes of the innate immune system have a critical role in detecting and eliminating fungal pathogens. We used patch clamp electrophysiology to explore the electrical signals elicited when macrophages engulf Candida albicans. In the perforated patch configuration, which is least disruptive to intracellular signaling, we detected a composite outwardly rectifying current during the engulfment of C. albicans or zymosan. FTY720, a known inhibitor of ion channel TRPM7, suppressed the current. We then tested the hypothesis that TRPM7 regulates the engulfment and clearance of C. albicans. We found that Trpm7-/- macrophages are highly deficient in the engulfment of C. albicans. Trpm7-/- macrophages initiate phagocytosis of yeast but are defective in sealing the phagocytic cups. While the precise mechanism through which TRPM7 regulates phagosome sealing is not clear, we tested the immunological significance of this discovery using a mouse model of systemic candidiasis. We show that in mice, wherein TRPM7 is deleted selectively in the myeloid cells, infection by C. albicans results in significantly higher lethality, increased colonization of vital organs and increased inflammatory cytokines in the blood. Our study establishes TRPM7 as an ion channel critical for the innate immune responses against fungal pathogens and sets the stage for cell biological studies that define the mechanisms through which TRPM7 regulates phagosome sealing. Significance statementThe worldwide increase in deadly or persistent fungal infections has prompted the research for alternative ways of treatment. We applied the specialized, perforated patch clamp technique to track and identify electrical currents elicited during the detection and engulfment of fungi by macrophages. The ion channel TRPM7 emerged as an important determinant of anti-fungal host defense as its deletion in the murine myeloid cells made the host mice highly susceptible to lethal candidiasis. Ion channels are attractive drug targets whose activation and inhibition can be manipulated with pharmacological therapeutics. This study raises the possibility of enhancing fungal clearance using activators of TRPM7. Such pharmacological strategy may benefit patients of persistent fungal infections that are recalcitrant to anti-fungal drugs.

immunology↗

bioRxiv2023

Novel TRPM7 inhibitors with potent anti-inflammatory effects in vivo

TRPM7, a TRP channel with ion conductance and kinase activities, has emerged as an attractive drug target for immunomodulation. Reverse genetics and cell biological studies have already established a key role for TRPM7 in the inflammatory activation of macrophages. Advancing TRPM7 as a viable molecular target for immunomodulation requires selective TRPM7 inhibitors with in vivo tolerability and efficacy. Such inhibitors have the potential to interdict inflammatory cascades mediated by systemic and tissue-specialized macrophages. FTY720, an FDA-approved drug for multiple sclerosis inhibits TRPM7. However, FTY720 is a prodrug and its metabolite, FTY720-phosphate, is a potent agonist of sphingosine 1-phosphate (S1P) receptors. In this study, we tested non-phosphorylatable FTY720 analogs, which are inert against S1PRs and well tolerated in vivo, for activity against TRPM7 and tissue bioavailability. Using patch clamp electrophysiology, we show that VPC01091.4 and AAL-149 block TRPM7 current at low micromolar concentrations. In culture, they act directly on macrophages to blunt LPS-induced inflammatory cytokine expression, an effect that is predominantly but not solely mediated by TRPM7. We found that VPC01091.4 has significant and rapid accumulation in the brain and lungs, along with direct anti-inflammatory action on alveolar macrophages and microglia. Finally, using a mouse model of endotoxemia, we show VPC01091.4 to be an efficacious anti-inflammatory agent that arrests systemic inflammation in vivo. Together, these findings identify novel small molecule inhibitors that allow TRPM7 channel inhibition independent of S1P receptor targeting. These inhibitors exhibit potent anti-inflammatory properties that are mediated by TRPM7 and likely other molecular targets that remain to be identified.

immunology↗