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Bull, D.

Publications and source records attributed to Bull, D..

2 recordsLinked to original sources
bioRxiv2023

The hypermorphic PLCγ2 S707Y variant dysregulates microglial cell function: insight into PLCγ2 activation in brain health and disease, and opportunities for therapeutic modulation.

Phospholipase C-gamma 2 (PLC{gamma}2) is highly expressed in hematopoietic and immune cells, where it is a key signalling node enabling diverse cellular functions. Within the periphery, gain-of-function (GOF) PLC{gamma}2 variants, such as the strongly hypermorphic S707Y, cause severe immune dysregulation. The milder hypermorphic mutation PLC{gamma}2 P522R increases longevity and confers protection in central nervous system (CNS) neurodegenerative disorders, implicating PLC{gamma}2 as a novel therapeutic target for treating these CNS indications. Currently, nothing is known about what consequences strong PLC{gamma}2 GOF has on CNS functionality, and more precisely on the specific biological functions of microglia. Using the PLC{gamma}2 S707Y variant as a model of chronic activation we investigated the functional consequences of strong PLC{gamma}2 GOF on human microglia. PLC{gamma}2 S707Y expressing human inducible pluripotent stem cells (hiPSC)-derived microglia exhibited hypermorphic enzymatic activity under both basal and stimulated conditions, compared to PLC{gamma}2 wild type. Despite the increase in PLC{gamma}2 enzymatic activity, the PLC{gamma}2 S707Y hiPSC-derived microglia display diminished functionality for key microglial processes including phagocytosis and cytokine secretion upon inflammatory challenge. RNA sequencing revealed a downregulation of genes related to innate immunity and response, providing molecular support for the phenotype observed. Our data suggests that chronic activation of PLC{gamma}2 elicits a detrimental phenotype that is contributing to unfavourable CNS functions, and informs on the therapeutic window for targeting PLC{gamma}2 in the CNS. Drug candidates targeting PLC{gamma}2 will need to precisely mimic the effects of the PLC{gamma}2 P522R variant on microglial function, but not those of the PLC{gamma}2 S707Y variant. HighlightsO_LIThe impact of strongly hypermorphic variants of PLC{gamma}2 have not been studied in brain and yet PLC{gamma}2 is implicated in modifying risk of CNS disorders including Alzheimers disease C_LIO_LITo address this, we explored the role of the strongly hypermorphic PLC{gamma}2 S707Y variant in hiPSC-derived microglia C_LIO_LIS707Y increases PLC{gamma}2 enzymatic activity and intracellular calcium flux C_LIO_LIPhagocytosis and cytokine production are diminished in PLC{gamma}2 S707Y microglia C_LIO_LIPLC{gamma}2 S707Y downregulates expression of genes related to innate immunity and response C_LIO_LIModulation of PLC{gamma}2 for therapy must recapitulate the positive effects of moderate hypermorphic variants on microglial functions whilst avoiding detrimental effects of strongly hypermorphic variants like PLC{gamma}2 S707Y C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=188 SRC="FIGDIR/small/564579v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@9f0903org.highwire.dtl.DTLVardef@108d26forg.highwire.dtl.DTLVardef@2fb691org.highwire.dtl.DTLVardef@7af80c_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗
bioRxiv2020

Paradoxical effects of cigarette smoke and COPD on SARS-CoV2 infection and disease

IntroductionHow cigarette smoke (CS) and chronic obstructive pulmonary disease (COPD) affect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and severity is controversial. We investigated the protein and mRNA expression of SARS-CoV-2 entry receptor ACE2 and proteinase TMPRSS2 in lungs from COPD patients and controls, and lung tissue from mice exposed acutely and chronically to CS. Also, we investigated the effects of CS exposure on SARS-CoV-2 infection in human bronchial epithelial cells. MethodsIn Cohort 1, ACE2-positive cells were quantified by immunostaining in FFPE sections from both central and peripheral airways. In Cohort 2, we quantified pulmonary ACE2 protein levels by immunostaining and ELISA, and both ACE2 and TMPRSS2 mRNA levels by RT-qPCR. In C57BL/6 WT mice exposed to air or CS for up to 6 months, pulmonary ACE2 protein levels were quantified by triple immunofluorescence staining and ELISA. The effects of CS exposure on SARS-CoV-2 infection were evaluated after 72hr in vitro infection of Calu-3 cells. After SARS-CoV-2 infection, the cells were fixed for IF staining with dsRNA-specific J2 monoclonal Ab, and cell lysates were harvested for WB of viral nucleocapsid (N) protein. Supernatants (SN) and cytoplasmic lysates were obtained to measure ACE2 levels by ELISA. ResultsIn both human cohorts, ACE2 protein and mRNA levels were decreased in peripheral airways from COPD patients versus both smoker and NS controls, but similar in central airways. TMPRSS2 levels were similar across groups. Mice exposed to CS had decreased ACE2 protein levels in their bronchial and alveolar epithelia versus air-exposed mice exposed to 3 and 6 months of CS. In Calu3 cells in vitro, CS-treatment abrogated infection to levels below the limit of detection. Similar results were seen with WB for viral N protein, showing peak viral protein synthesis at 72hr. ConclusionsACE2 levels were decreased in both bronchial and alveolar epithelial cells from uninfected COPD patients versus controls, and from CS-exposed versus air-exposed mice. CS-pre-treatment did not affect ACE2 levels but potently inhibited SARS-CoV-2 replication in this in vitro model. These findings urge to further investigate the controversial effects of CS and COPD on SARS-CoV2 infection.

immunology↗