Biology subjects

White, C. J.

Publications and source records attributed to White, C. J..

8 recordsLinked to original sources

bioRxiv2026

Aging, HIV Status, and Sex Differentially Influence Antiretroviral Therapy Disposition Pathways in Rectosigmoid Tissue and Peripheral Blood Mononuclear Cells

People living with human immunodeficiency virus (HIV) are increasingly surviving into older age due to the effectiveness of antiretroviral (ARV) therapy (ART), creating a growing population in whom age-related changes may influence treatment outcomes. Although aging is known to affect drug disposition, the molecular mechanisms by which aging alters ARV pharmacology remain incompletely understood, particularly within tissue compartments, including the rectosigmoid region of the colon, that serve as sites of HIV transmission and persistence. To address this knowledge gap, we used proteomics by liquid chromatography-mass spectrometry (LC-MS) to evaluate the impact of age and HIV status on proteins and pathways relevant to ARV disposition in peripheral blood mononuclear cells (PBMC) and rectosigmoid colon tissue obtained from young (18-50) HIV-seronegative adults, older (65-80) HIV-seronegative adults, and older virally suppressed people living with HIV. We found that aging and HIV infection differentially influenced proteins predominantly within nucleos(t)ide reverse transcriptase inhibitor (NRTI) pathways, in rectosigmoid tissue and PBMC. HIV-associated effects to the proteome were more prominent in PBMC, whereas aging produced broader alterations in ARV disposition-related proteins in rectosigmoid tissue, including proteins involved in drug transport, intracellular drug activation, dephosphorylation, and nucleotide homeostasis. Several age-associated changes were further influenced by biologic sex, suggesting that aging may not affect ARV disposition uniformly across populations. To place these findings within a broader context, pathway analyses were performed that identified extensive tissue-specific remodeling associated with aging and HIV infection involving drug disposition, immune regulation, cellular metabolism, and disease-related pathways. Notably, aging was associated with alterations in pathways relevant to nucleotide metabolism and gastrointestinal tissue function, suggesting that processes beyond traditional drug transport and metabolism pathways may contribute to variability in ARV disposition with advancing age. Together, these findings identify aging as an important modifier of pathways that regulate ARV disposition within compartments relevant to HIV transmission and persistence. While the clinical consequences of our findings are unknown, these data provide a mechanistic foundation for future studies investigating whether age-associated changes influence the effectiveness of ART and HIV pre-exposure prophylaxis in older adults.

pharmacology and toxicology↗

bioRxiv2026

Primary Human Macrophages Exhibit Functional CYP3A4 Activity with Marked Expression-Function Discordance and Cocaine-Induced Catalytic Activation

CYP3A4 is a phase I drug-metabolizing enzyme responsible for transformation of ~50% of clinically relevant drugs. While extensively characterized in hepatocytes, its role in immune cells remains poorly understood. Here, using primary human monocyte-derived macrophages, we identify an understudied extrahepatic site of CYP3A4-mediated drug metabolism. Macrophages from 100 independent donors expressed CYP3A4 and its transcriptional regulators, Pregnane X Receptor (PXR) and Constitutive Androstane Receptor (CAR), with substantial interindividual variability. Importantly, CYP3A4 protein expression was accompanied by measurable catalytic activity in intact macrophages, yet CYP3A4 mRNA, protein abundance, and activity lacked concordance, demonstrating that expression alone may not predict function. In vivo, CYP3A4 was expressed in rhesus macaque Kupffer cells, further supporting macrophages as a potential pharmacologic entity. We next evaluated cocaine as a potential modulator of CYP3A4, due to its role in xenobiotic clearance. Cocaine had a dichotomous effect on expression, increasing CYP3A4 in some donors while producing no change or decreases in others, a phenotype associated with PXR, CAR, and the sigma-1 cocaine receptor. Strikingly, despite these divergent expression responses, cocaine increased CYP3A4 catalytic activity in all donors, reaching or exceeding levels induced by rifampicin, a clinically relevant CYP3A4 inducer. In rhesus macaques, cocaine also decreased antiretroviral therapy tissue concentrations, coincident with increased CYP3A4 and PXR. Together, these findings establish macrophages as a functionally active extrahepatic site of CYP3A4 metabolism and reveal a critical disconnect between CYP3A4 expression and catalytic function. Moreover, our findings identify interindividual variability and expression-activity discordance as important considerations for personalized medicine and understanding clinically relevant drug-drug interactions in the context of substance use.

pharmacology and toxicology↗

bioRxiv2026

Simian Immunodeficiency Virus and Antiretroviral Therapy Impact Rhesus Macaque Brain Lipid Distribution

Human immunodeficiency virus (HIV) infection promotes considerable bioenergetic, spatially heterogenous strain to the brain that is incompletely ameliorated through viral suppression afforded by antiretroviral therapy (ART). Disrupted homeostasis of brain lipids after HIV in humans or simian immunodeficiency virus (SIV) infection in rhesus macaques occurs due to elevated energetic demands, neuroinflammation, reactive oxygen species, and barrier leakiness. Brain lipids are particularly vulnerable to HIV-associated dysregulation due to their high abundance, unique composition, and specialized functional roles. Using rhesus macaques exposed to SIV and ART (tenofovir disoproxil fumarate (TDF), emtricitabine (FTC), and dolutegravir (DTG), we investigated the spatial distribution and abundance of lipids across brain regions and metabolically relevant peripheral tissues using mass spectrometry imaging. When comparing lipid abundance, individual lipids representing a multitude of species were more varied across tissues than by treatment condition. Further, we discerned either solely SIV infection or ART outweighed one another in altering phospholipids in different tissues Presence of ART had a greater influence on phospholipid homeostasis in the temporal cortex and hippocampus than in the midbrain, possibly due to differences in penetrance and turnover of ART across brain regions. Overall, these data demonstrate ART robustly increased phospholipids across brain regions while SIV infection had a varied impact depending on the brain region. These findings inform the need to further evaluate the neurologic consequences that may result in the brain due to disrupted lipid homeostasis across ART regimens.

pharmacology and toxicology↗

bioRxiv2024

Deepening biomedical research training: Community-Building Wellness Workshops for Post-Baccalaureate Research Education Program (PREP) Trainees

ProblemAll trainees, especially those from historically minoritized backgrounds, experience stresses that may reduce their continuation in science, technology, engineering, math, and medicine (STEMM) careers. The Johns Hopkins University School of Medicine is one of [~]45 institutions with a National Institutes of Health funded Postbaccalaureate Research Education Program (PREP) that provides mentoring and a year of fulltime research to prepare students from historically excluded groups for graduate school. Having experienced the conflation of stresses during the COVID-19 pandemic and related shutdown, we realized our program lacked a component that explicitly helped PREP Scholars recognize and cope with non-academic stresses (financial, familial, social, mental) that might threaten their confidence and success as scientists and future in STEMM. InterventionWe developed an early-intervention program to help Scholars develop life-long skills to become successful and resilient scientists. We developed a year-long series comprised of 9 workshops focused on community, introspection, financial fitness, emotional intelligence, mental health, and soft-skills. We recruited and compensated a cohort of PhD students and postdoctoral fellows to serve as Peer Mentors, to provide a community and the safest space for Scholars to discuss personal concerns. Peer Mentors were responsible for developing and facilitating these Community-Building Wellness Workshops (CBWW). ContextCBWW were created and exectued as part of the larger PREP program. Workshops included a PowerPoint presentation by Peer Mentors that featured several case studies that prompted discussion and provided time for small-group discussions between Scholars and Peer Mentors. We also included pre- and post-work for each workshop. These touch-points helped Scholars cultivate the habit of introspection. ImpactThe CBWW exceeded our goals. Both Peer Mentors and Scholars experienced strong mutual support, and Scholars developed life-long skills. Notably, several Scholars who had been experiencing financial, mental or mentor-related stress immediately brought this to the attention of program leadership, allowing early and successful intervention. At the completion of CBWW, PREP Scholars reported implementing many workshop skills into practice, were reshaping their criteria for choosing future mentors, and evaluating career decisions. Strikingly, Peer Mentors found they also benefitted from the program as well, suggesting a potential larger scope for the role of CBWW in academia. Lessons LearnedPeer Mentors were essential in creating a safe supportive environment that facilitated discussions, self-reflection, and self-care. Providing fair compensation to Peer Mentors for their professional mentoring and teaching contributions was essential and contributed meaningfully to the positive energy and impact of this program.

scientific communication and education↗

bioRxiv2023

The Endosomal pH Regulator NHE6 is Required for Insulin-Stimulated Glucose Uptake in Adipocytes

ObjectiveTrafficking of GLUcose Transporter isoform 4 (GLUT4) from the adipocyte vesicular pool to the cell surface is tightly regulated by insulin to maintain glucose homeostasis in response to changing demands in energy consumption. Previously, endosomal Na+/H+ exchanger 6 (NHE6, gene name SLC9A6) was identified in adipocyte plasma membranes and shown to associate with GLUT4-positive vesicles. However, the functional contribution of NHE6 to GLUT4 trafficking and glucose uptake remained uncharacterized. MethodsNHE6 was knocked down in 3T3L1 cells either before or after differentiation into adipocytes using lentiviral delivery of shRNA. Uptake of [3H] 2-deoxyglucose into adipocytes was quantified in response to insulin. We used epitope tagged constructs to distinguish between localization of vesicular and surface levels of NHE6 and GLUT4 proteins. Protein and transcript levels of components of the glucose signaling pathway were monitored by qPCR and Western analysis, respectively, in response to NHE6 knockdown and/or treatment with chemical modulators of endosomal pH. ResultsWe show that insulin-stimulated glucose uptake in adipocytes is severely impaired upon NHE6 depletion. Correspondingly, insulin-stimulated surface expression of GLUT4 at the adipocyte plasma membrane was diminished in NHE6 knockdown cells due to a post-transcriptional decrease in basal GLUT4. Metformin response of GLUT4 was also muted in the absence of NHE6. Further, we demonstrate diminished activation of the GLUT4 translocation pathway in the absence of NHE6 via reduced expression of the insulin receptor and reduced phosphorylation of the downstream effector kinase Akt. Components of GLUT4 storage vesicles, including GLUT4, LRP1 and sortilin were downregulated in NHE6-knockdown adipocytes under basal conditions. Proteostatic control of key components of the insulin signaling pathway (insulin receptor, GLUT4) could be restored by chemical bypass of NHE6 using the V-ATPase inhibitor bafilomycin or the Na+/H+ exchanger mimetic monensin. ConclusionsThus, NHE6 is critical for proper expression and trafficking of GLUT4. Basal expression of both insulin receptor and GLUT4 in NHE6 knockdown cells could be restored by bafilomycin-inhibition of the H+-ATPase or the H+ ionophore monensin pointing to pH dysregulation as the underlying defect. We suggest that NHE6 is a component of GLUT4 storage vesicles where it regulates proteostasis. These findings establish NHE6 as a novel contributor to glucose homeostasis and energy metabolism with implications for Christianson syndrome patients who carry loss of function mutations in the SLC9A6 gene. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=147 SRC="FIGDIR/small/551163v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@f6fc88org.highwire.dtl.DTLVardef@13d7faforg.highwire.dtl.DTLVardef@89d577org.highwire.dtl.DTLVardef@11da50a_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2023

Roadmap for Canonical and Extended Endocannabinoid System Receptors in Peripheral Organs of Preclinical Animal Models

The endocannabinoid system is widely expressed throughout the body and is comprised of receptors, ligands, and enzymes that maintain metabolic, immune, and reproductive homeostasis. Increasing interest in the endocannabinoid system has arisen due to these physiologic roles, policy changes leading to more widespread recreational use, and the therapeutic potential of Cannabis and phytocannabinoids. Rodents have been the primary preclinical model of focus due to their relative low cost, short gestational period, genetic manipulation strategies, and gold-standard behavioral tests. However, the potential for lack of clinical translation to non-human primates and humans is high as cross-species comparisons of the endocannabinoid system has not been evaluated. To bridge this gap in knowledge, we evaluate the relative gene expression of 14 canonical and extended endocannabinoid receptors in seven peripheral organs of C57/BL6 mice, Sprague-Dawley rats, and non-human primate rhesus macaques. Notably, we identify species- and organ-specific heterogeneity in endocannabinoid receptor distribution where there is surprisingly limited overlap among the preclinical models. Importantly, we determined there were only five receptors (CB2, GPR18, GPR55, TRPV2, and FAAH) that had identical expression patterns in mice, rats, and rhesus macaques. Our findings demonstrate a critical, yet previously unappreciated, contributor to challenges of rigor and reproducibility in the cannabinoid field, which has profound implications in hampering progress in understanding the complexity of the endocannabinoid system and development of cannabinoid-based therapies.

molecular biology↗

bioRxiv2022

Antiretroviral Therapy Does Not Restore Brain Lipids During SIV Infection: Regional Analysis of Metabolic Homeostasis and Depletion

Human immunodeficiency virus (HIV) infection continues to promote neurocognitive impairment, mood disorders, and brain atrophy even in the modern era of viral suppression. Brain lipids are vulnerable to HIV-associated energetic strain and contribute to HIV-associated neurologic dysfunction due to alterations in lipid breakdown and structural lipid composition. HIV neuropathology is region dependent, yet there has not been comprehensive characterization of the spatial heterogeneity of brain lipids during infection that may impact neurologic function. To address this gap, we evaluated the spatial lipid distribution using matrix laser desorption/ionization imaging mass spectrometry (MALDI-IMS) across four brain regions (parietal cortex, midbrain, thalamus, and temporal cortex), as well as kidney for a peripheral tissue control, in a virally suppressed simian immunodeficiency virus (SIV)-infected rhesus macaque. We assessed lipids indicative of fat breakdown [acylcarnitines (CARs)] and critical structural lipids [phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs)] across fatty acid chain lengths and degrees of unsaturation. CARs with very long-chain, polyunsaturated fatty acids (PUFAs) were more abundant across all brain regions than shorter chain, saturated or monounsaturated species. We observed distinct brain lipid distribution patterns for CARs and PCs. However, no clear expression patterns emerged for PEs. Surprisingly, kidney was nearly devoid of ions corresponding to PUFAs common in brain. PEs and PCs with PUFAs had little intensity and less density than other species and, only one CAR species was observed in kidney at high intensity. Overall, our study provides substantial evidence for persistent bioenergetic changes to the brain despite viral suppression, including region-dependent mobilization of CARs for oxidation and disparities in the presence of key phospholipids necessary for maintaining proper brain structure and function. These data indicate that region-specific interventions to restore proper lipid metabolism are essential for treating HIV neurologic disease in the era of antiretroviral therapy. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=136 SRC="FIGDIR/small/508302v3_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@598d53org.highwire.dtl.DTLVardef@14d5cf1org.highwire.dtl.DTLVardef@10f6c9org.highwire.dtl.DTLVardef@1ba1aab_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

pathology↗

bioRxiv2021

MONTE enables serial immunopeptidome, ubiquitylome, proteome, phosphoproteome, acetylome analyses of sample-limited tissues

Serial multiomic analyses of proteome, phosphoproteome and acetylome provides functional insights into disease pathology and drug effects while conserving precious human material. To date, ubiquitylome and HLA peptidome analyses have required separate samples for parallel processing each using distinct protocols. Here we present MONTE, a highly-sensitive multi-omic native tissue enrichment workflow that enables serial, deepscale analysis of HLA-I and HLA-II immunopeptidome, ubiquitylome, proteome, phosphoproteome and acetylome from the same tissue samples. We demonstrate the capabilities of MONTE in a proof-of-concept study of primary patient lung adenocarcinoma(LUAD) tumors. Depth of coverage and quantitative precision at each of the omes is not compromised by serialization, and the addition of HLA immunopeptidomics enables identification of putative immunotherapeutic targets such as cancer/testis antigens and neoantigens. MONTE can provide insights into disease-specific changes in antigen presentation, protein expression, protein degradation, cell signaling, cross-talk and epigenetic pathways involved in disease pathology and treatment.

cancer biology↗