Biology subjects

Mullick, A. E.

Publications and source records attributed to Mullick, A. E..

9 recordsLinked to original sources

bioRxiv2026

Deletion of LRP1 in Smooth Muscle Cells Induces Infrarenal Aortic Aneurysms in Mice

Background: Low-density lipoprotein receptor-related protein 1 (LRP1) in smooth muscle cells (SMCs) is essential for maintaining aortic wall integrity. This study investigated whether deletion of LRP1 in SMCs induces region-specific aortic pathology and evaluated a potential therapeutic strategy. Methods: Lrp1-floxed mice were bred with Sm22-Cre+/0 mice to generate mice with SMC-LRP1 deletion (SMC-LRP1-/-) and wild-type littermates (SMC-LRP1+/+). Micro-computed tomography (micro-CT) was used to visualize the aorta, and aortic tissue sections were characterized histologically. To evaluate a potential therapeutic strategy, antisense oligonucleotides (ASOs) targeting hepatocyte-derived angiotensinogen (AGT) were administered to inhibit AGT synthesis. Results: Immunostaining and Western blotting confirmed LRP1 deletion in aortic SMCs. At 40 weeks of age, micro-CT revealed marked increases in aortic width and volume. Although dilatation occurred throughout the aorta, the infrarenal region exhibited the greatest expansion in both male and female SMC-LRP1-/- mice compared with SMC-LRP1+/+ littermates; subsequent analyses therefore focused on this region. LRP1 deletion in SMCs caused pronounced SMC loss and increased collagen deposition in the infrarenal aorta. Inhibition of hepatocyte-derived AGT with ASO attenuated infrarenal aortic dilatation and preserved aortic wall integrity in both male and female mice. Conclusions: Deletion of LRP1 in SMCs causes progressive aortic dilatation that includes the infrarenal aorta. Pharmacologic inhibition of hepatocyte-derived AGT attenuates infrarenal aortic dilatation.

pathology↗

bioRxiv2026

Angiotensin II Promotes Mitral Valve and Left Atrial Pathology in Fibrillin-1C1041G/+ Mice

Background: Activation of the renin-angiotensin system (RAS) contributes to aortic diseases caused by fibrillin-1 haploinsufficiency (Fbn1C1041G/+). However, whether RAS activation influences mitral valve disease associated with FBN1 variants remains undefined. This study determined whether inhibition or augmentation of the RAS affects mitral valve pathology in Fbn1C1041G/+ mice. Methods: Angiotensinogen (AGT) antisense oligonucleotides (ASOs) were administered for 12 weeks to inhibit the RAS in male and female Fbn1C1041G/+ mice. To augment the RAS, mice were infused with angiotensin II (AngII; 1,000 ng/kg/min) for 28 days. Mitral valve and heart function were monitored by ultrasound. At termination, hearts were dissected free and tissue sectioned to assess mitral valve leaflet thickness and pathology. Results: Mitral valve leaflet thickness was significantly increased in Fbn1C1041G/+ mice compared to Fbn1+/+ littermates of both sexes. ASO-mediated AGT inhibition did not alter this phenotype despite markedly reduced plasma AGT concentrations. AngII infusion increased mitral valve leaflet thickness in Fbn1C1041G/+ mice with increased proteoglycan and collagen content, while exerting minimal effects in Fbn1+/+ mice. Twenty-five percent of AngII-infused Fbn1C1041G/+ mice died of non-vascular causes. Ultrasound showed mitral valve dysfunction in AngII-infused Fbn1C1041G/+ mice. Grossly expanded left atria were common in AngII-infused Fbn1C1041G/+ mice. These markedly enlarged left atria contained increased fibrosis, macrophage accumulation, and platelet-rich masses. Conclusions: Mitral valves of Fbn1C1041G/+ mice did not respond to AGT inhibition but were markedly more susceptible to AngII infusion, with greater increases in thickness and compositional changes than mitral valves of Fbn1+/+ mice. In addition, AngII promoted mitral valve dysfunction that were associated with pronounced left atrial pathology.

pharmacology and toxicology↗

bioRxiv2025

Sex- and ketogenesis-dependent effects of intermittent fasting against diet-induced obesity and fatty liver disease

ABSTRACTSIntermittent fasting (IF) improves metabolic health, yet the requirement for hepatic ketogenesis in mediating these benefits remains unclear. Here, we investigated how hepatic ketogenesis contributes to the metabolic and hepatic effects of IF in male and female mice. In the human liver, ketogenesis-associated genes showed sex-dependent correlations with inflammatory and fibrotic pathways. In mice, fasting increased circulating ketone bodies, with females exhibiting a greater rise, indicating intrinsic sex differences in ketone metabolism. IF reduced body weight and adiposity in both sexes, and these systemic benefits persisted despite antisense oligonucleotide (ASO)-mediated knockdown of hepatic Hmgcs2. In contrast, hepatic benefits were sex- and ketogenesis-dependent. IF markedly reduced steatosis and fibrosis in male mice, but these improvements were attenuated or abolished when hepatic ketogenesis was disrupted. Female mice showed minimal hepatic benefit from IF and displayed heightened susceptibility to steatosis, fibrosis, and inflammatory activation under ketogenic insufficiency. Single-cell transcriptomic analyses identified neutrophils and myofibroblasts as key responders to hepatocyte-derived ketone bodies, and IF suppressed neutrophil-driven inflammatory signaling in a ketogenesis-dependent manner in males but not females. Together, these findings demonstrate that while systemic metabolic improvements from IF are largely ketogenesis-independent, the hepatic anti-steatotic and anti-fibrotic effects of IF are sexually dimorphic and require intact hepatic ketogenesis.

physiology↗

bioRxiv2025

The Lipid Hydrolase ABHD6 is a Therapeutic Target in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)-Related Hepatocellular Carcinoma

Primary liver cancer accounts for approximately 700,000 deaths worldwide annually ranking third in cancer-related mortality, with hepatocellular carcinoma (HCC) comprising the majority of these tumors. Metabolic dysfunction-associated steatotic liver disease (MASLD) is currently a leading cause of HCC in the United States. We previously identified the lipid hydrolase alpha/beta hydrolase domain 6 (ABHD6) as a key mediator of the development of metabolic syndrome and intimately involved in cell signaling, making it a prime target for investigation in MASLD-related HCC. ABHD6 displays higher expression within HCC tumor cores when compared to adjacent non-tumor liver tissue in human subjects. Using an in vivo antisense oligonucleotide (ASO)-driven knockdown approach, we have shown the inhibition of ABHD6 prevents the development and progression of HCC in an obesity/MASLD-driven mouse model. Additionally, a xenograft model using the human Huh7 cell line displayed reduced tumor engraftment and growth with ABHD6 genetic deletion and small molecule inhibition. ABHD6 knockout cells demonstrated increased levels of bis(monoacylglycerol)phosphates (BMPs), lipids relevant to high fat diet-induced lysosomal dysfunction, and knockout cells also demonstrated altered autophagy and lysosomal activity using in vitro model of saturated fatty acid-induced lipotoxicity. These studies reveal novel lipid signaling mechanisms by which MASLD progresses towards HCC and provide support for ABHD6 as a therapeutic target in HCC. SignificanceWe have identified that alpha/beta hydrolase domain 6 (ABHD6) plays a role in lysosomal membrane lipid remodeling pathways that are relevant in obesity/MASLD-driven HCC. Inhibitors targeting ABHD6 reorganize lysosomal lipid homeostasis to improve outcomes in HCC.

cancer biology↗

bioRxiv2024

Renal Proximal Tubule Cell-specific Megalin Deletion Induces Tubulointerstitial Nephritis in Mice Fed Western Diet

BackgroundPharmacological inhibition of megalin (also known as low-density lipoprotein receptor-related protein 2: LRP2) attenuates atherosclerosis in hypercholesterolemic mice. Since megalin is abundant in renal proximal tubule cells (PTCs), the purpose of this study was to determine whether PTC-specific deletion of megalin reduces hypercholesterolemia-induced atherosclerosis in mice. MethodsFemale Lrp2 f/f mice were bred with male Ndrg1-Cre ERT2 +/0 mice to develop PTC-LRP2 +/+ and -/- littermates. To study atherosclerosis, all mice were bred to an LDL receptor -/- background and fed a Western diet to induce atherosclerosis. ResultsPTC-specific megalin deletion did not attenuate atherosclerosis in LDL receptor -/- mice in either sex. Serendipitously, we discovered that PTC-specific megalin deletion led to interstitial infiltration of CD68+ cells and tubular atrophy. The pathology was only evident in male PTC-LRP2 -/- mice fed the Western diet, but not in mice fed a normal laboratory diet. Renal pathologies were also observed in male PTC-LRP2 -/- mice in an LDL receptor +/+ background fed the same Western diet, demonstrating that the renal pathologies were dependent on diet and not hypercholesterolemia. In contrast, female PTC-LRP2 -/- mice had no apparent renal pathologies. In vivo multiphoton microscopy demonstrated that PTC-specific megalin deletion dramatically diminished albumin accumulation in PTCs within 10 days of Western diet feeding. RNA sequencing analyses demonstrated the upregulation of inflammation-related pathways in kidney. ConclusionsPTC-specific megalin deletion does not affect atherosclerosis, but leads to tubulointerstitial nephritis in mice fed Western diet, with severe pathologies in male mice.

pathology↗

bioRxiv2023

Antisense Oligonucleotide Targeting Hepatic Serum Amyloid A Limits the Progression of Angiotensin II-Induced Abdominal Aortic Aneurysm Formation

Background and aimObesity increases the risk for abdominal aortic aneurysms (AAA) in humans and enhances angiotensin II (AngII)-induced AAA formation in C57BL/6 mice. We reported that deficiency of SAA significantly reduces AngII-induced inflammation and AAA in both hyperlipidemic apoE-deficient and obese C57BL/6 mice. The aim of this study is to investigate whether SAA plays a role in the progression of early AAA in obese C57BL/6 mice. MethodsMale C57BL/6J mice were fed a high-fat diet (60% kcal as fat) throughout the study. After 4 months of diet, the mice were infused with AngII until the end of the study. Mice with at least a 25% increase in the luminal diameter of the abdominal aorta after 4 weeks of AngII infusion were stratified into 2 groups. The first group received a control antisense oligonucleotide (Ctr ASO), and the second group received ASO that suppresses SAA (SAA-ASO) until the end of the study. ResultsPlasma SAA levels were significantly reduced by the SAA ASO treatment. While mice that received the control ASO had continued aortic dilation throughout the AngII infusion periods, the mice that received SAA-ASO had a significant reduction in the progression of aortic dilation, which was associated with significant reductions in matrix metalloprotease activities, decreased macrophage infiltration and decreased elastin breaks in the abdominal aortas. ConclusionsWe demonstrate for the first time that suppression of SAA protects obese C57BL/6 mice from the progression of AngII-induced AAA. Suppression of SAA may be a therapeutic approach to limit AAA progression.

pathology↗

bioRxiv2021

Renal Angiotensinogen in Nonhuman Primates is Predominantly Liver-Derived

AGT (Angiotensinogen) is the unique substrate of the renin-angiotensin system. Liver is the primary source of circulating AGT. The present study determined whether hepatocyte-derived AGT regulates renal AGT accumulation by injecting ASO (antisense oligonucleotides) targeting hepatocyte-derived AGT (GalNAc AGT ASO) into female cynomolgus monkeys. Hepatocyte-specific inhibition of AGT led to profound reductions of plasma AGT concentrations. AGT protein in S1 and S2 of renal proximal tubules was greatly diminished by GalNAc AGT ASO. Given the similarity between nonhuman primates and human, our findings support the notion that renal AGT is predominantly derived from liver, and liver regulates renal angiotensin II production in humans. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=148 SRC="FIGDIR/small/444555v2_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@292f5aorg.highwire.dtl.DTLVardef@1e3e0aborg.highwire.dtl.DTLVardef@1b331e3org.highwire.dtl.DTLVardef@1904dba_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2020

Effects of Renin-Angiotensin Inhibition on ACE2 and TMPRSS2 Expression

Angiotensin-converting enzyme 2 (ACE2), a component of the renin-angiotensin system, is a receptor for SARS-CoV-2, the virus that causes COVID-19. To determine whether the renin-angiotensin inhibition regulates ACE2 expression, either enalapril (an angiotensin-converting enzyme inhibitor) or losartan (an AT1 receptor blocker) was infused subcutaneously to male C57BL/6J mice for two weeks. Neither enalapril nor losartan changed abundance of ACE2 mRNA in lung, ileum, kidney, and heart. Viral entry also depends on transmembrane protease serine 2 (TMPRSS2) to prime the S protein. TMPRSS2 mRNA was abundant in lungs and ileum, modest in kidney, but barely detectable in heart. TMPRSS2 mRNA abundance was not altered by either enalapril or losartan in any of the 4 tissues. Next, we determined whether depletion of angiotensinogen (AGT), the unique substrate of the renin-angiotensin system, changes ACE2 and TMPRSS2 mRNA abundance. AGT antisense oligonucleotides (ASO) were injected subcutaneously to male C57BL/6J mice for 3 weeks. Abundance of ACE2 mRNA was unchanged in any of the 4 tissues, but TMPRSS2 mRNA was significantly decreased in lungs. Our data support that the renin-angiotensin inhibition does not regulate ACE2 and hence are not likely to increase risk for COVID-19.

molecular biology↗

bioRxiv2020

Inhibition of Angiotensin II Dependent AT1a Receptor Stimulation Attenuates Thoracic Aortic Pathology in Fibrillin-1C1041G/+ Mice

Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=157 SRC="FIGDIR/small/127670v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@8e7c32org.highwire.dtl.DTLVardef@7bf57aorg.highwire.dtl.DTLVardef@312d3forg.highwire.dtl.DTLVardef@9198bd_HPS_FORMAT_FIGEXP M_FIG C_FIG ObjectiveA cardinal feature of Marfan syndrome is thoracic aortic aneurysm (TAA). The contribution of ligand-dependent stimulation of angiotensin II receptor type 1a (AT1aR) to TAA progression remains controversial because the beneficial effects of angiotensin receptor blockers have been ascribed to off-target effects. This study used genetic and pharmacologic modes of attenuating angiotensin receptor and ligand, respectively, to determine their roles on TAA in mice with fibrillin-1 haploinsufficiency (Fbn1C1041G/+). Approach and ResultsTAA in Fbn1C1041G/+ mice were determined in both sexes and found to be strikingly sexual dimorphic. Males displayed progressive dilation over 12 months while ascending aortic dilation in Fbn1C1041G/+ females did not differ significantly from wild type mice. To determine the role of AT1aR, Fbn1C1041G/+ mice that were either +/+ or -/- for AT1aR were generated. AT1aR deletion reduced progressive expansion of ascending aorta and aortic root diameter from 1 to 12 months of age in males. Medial thickening and elastin fragmentation were attenuated. An antisense oligonucleotide against angiotensinogen (AGT-ASO) was administered to male Fbn1C1041G/+ mice to determine the effects of angiotensin II depletion. AGT-ASO administration, at doses that markedly reduced plasma AGT concentrations, attenuated progressive dilation of the ascending aorta and aortic root. AGT-ASO also reduced medial thickening and elastin fragmentation. ConclusionsGenetic approaches to delete AT1aR and deplete AngII production exerted similar effects in attenuating pathology in the proximal thoracic aorta of male Fbn1C1041G/+ mice. These data are consistent with ligand (AngII) dependent stimulation of AT1aR being responsible for aortic disease progression. HighlightsO_LIProfound sexual dimorphism of aortic disease occurs in Fbn1C1041G/+ mice, with female mice being more resistant and male mice being more susceptible. C_LIO_LIInhibition of the AngII-AT1aR axis attenuates aortic pathology in male Fbn1C1041G/+ mice. C_LIO_LIAntisense oligonucleotides targeting angiotensinogen deplete plasma angiotensinogen and attenuate thoracic aortic aneurysms. C_LI

physiology↗