About

Anne Knowlton, M.D., is a Professor Emeritus in the Department of Internal Medicine, Cardiology at the UC Davis School of Medicine. Her research focuses on vascular inflammation, exosomes, and their roles in aging and dementia. She investigates the biological functions of exosomes in disease and regeneration, emphasizing their involvement in endothelial senescence and vascular dysfunction. Her work also explores the molecular mechanisms underlying cardiovascular diseases, including the role of heat shock proteins, mitochondrial dynamics, and cellular communication in cardiac health and disease. Dr. Knowlton has contributed significantly to understanding how aging, estrogen loss, and oxidative stress impact vascular and cardiac function, employing multiomics profiling and proteomics approaches to elucidate these processes.

Research topics

• Biology
• Cell biology
• Biochemistry
• Genetics
• Endocrinology
• Medicine
• Immunology

Selected publications

• Multiomics Profiling of Extracellular Vesicles Supports Their Involvement in Endothelial Senescence‐Associated Vascular Dysfunction

  Journal of Extracellular Biology · 2025-07-30

  articleOpen access

  Dysfunction of vascular endothelium is characteristic of many aging-related diseases, including Alzheimer's disease (AD) and AD-related dementias (ADRD). Although it is widely posited that endothelial cell dysfunction contributes to the pathogenesis and/or progression of AD/ADRD, it is not clear how. A plausible hypothesis is that intercellular trafficking of extracellular vesicles (EVs) from senescent vascular endothelial cells promotes vascular endothelial cell dysfunction. To test this hypothesis, we compared the expression of proteins and miRNAs in EVs isolated from four sets of genetically identical early passage non-senescent (EP) versus late passage senescent (SEN) primary human coronary artery endothelial cells (HCAECs) derived from four donors. Proteomics and miRNA libraries constructed from these EV isolates were evaluated using FunRich gene ontology analysis to compare functional enrichment between EP and SEN endothelial cell EVs (ECEVs). Replicative senescence was associated with altered EV abundance and contents independent of changes in EV size. Unique sets of miRNAs and proteins were differentially expressed in SEN-ECEVs, including molecules related to cell adhesion, barrier integrity, receptor signalling, endothelial-mesenchymal transition and cell senescence. miR-181a-5p was the most upregulated miRNA in SEN-ECEVs, increasing >5-fold. SEN-ECEV proteomes supported involvement in several pro-inflammatory pathways consistent with senescence and the senescence-associated secretory phenotype (SASP). These data indicate that SEN-ECEVs are enriched in bioactive molecules implicated in senescence-associated vascular dysfunction, blood-brain barrier impairment, and AD/ADRD pathology. These observations suggest involvement of SEN-ECEVs in the pathogenesis of vascular dysfunction associated with AD/ADRD.

  PublisherOA PDFDOI

• Panel discussion: Publishing

  2024-06-06

  preprint
  PublisherDOI

• Session 1 (Part 1) - Making the most of Next Generation Scientists (a panel discussion)

  2023-07-02

  preprint1st authorCorresponding

  This panel session and Q A will introduce the Next Generation Scientists Symposium, and how you as a delegate can make the most of your time, as well as additional career insights and perspectives. Alistair Hetherington will chair the discussions.

  PublisherDOI

• Abstract 15451: Regulations of Nrf2 by Nf-κB in Ischemic Heart Failure

  Circulation · 2023-11-07

  articleSenior author

  Introduction: Oxidative stress is an important pathophysiological factor in the development and progression of ischemic heart failure (IHF). Nuclear factor E2-related factor 2 (Nrf2) is a major regulator of the protective antioxidant response and has been found to decrease by 50% in IHF. However, the mechanism of Nrf2 downregulation remains incompletely understood. NF-kB is a critical transcription factor that influences many cellular processes and is activated in IHF with increased reactive oxygen species (ROS). We hypothesize that activation of NF-kB may underlie the decreased Nrf2 activity in IHF. Methods and Results: To induce IHF, we performed left anterior descending coronary artery (LAD) ligation surgery in Sprague Dawley rats and FVB/NJ mice. We found a significant reduction in cardiac function after LAD surgery in ischemia/reperfusion (I/R) mice relative to sham-operated mice using echocardiography. Tissue sample analyses reveal a crucial role of NF-kB activation in the regulation of Nrf2 in IHF. Additionally, after 2 weeks of I/R, we found that rats treated with Nrf2 overexpressed lentivirus demonstrated greater pressure development than rats with vehicle treatment. Using rat cardiac myoblast cells (H9C2) and western blot analysis, we tested the expression of cytosolic and nuclear Nrf2 and p65 (a component of NF-kB) following time- and dose-dependent treatments of H2O2. We found that p65 activation inhibited Nrf2 activity, while inhibitions of p65 nuclear translocation prevented the decrease in Nrf2 nuclear activities. We then generated a knockout of p65 in H9C2 cells and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) using CRISPR-Cas9 technology to test NF-κB regulation on the Nrf2 activities, which further strengthened our previous findings. Conclusions: Taken together, our data support the critical role of NF-kB activation in the regulation of Nrf2 in IHF, providing new insights into possible molecular targets for the treatment of IHF through the regulation of the protective antioxidant response.

  PublisherDOI

• Effects of Senescent Human Endothelial Cells on Neuronal Viability and Neurite Outgrowth Are Not IL‐8‐ or Serpin E1‐Dependent

  The FASEB Journal · 2022-05-01

  article

  It is estimated that more than 50% of adults over 80 will develop dementia, including Alzheimer’s disease (AD), and the primary risk factor for dementia is aging. Aging provides the substrate for disease through increased inflammation and cellular dysfunction, which in turn sets the stage for neurodegenerative disease. In a previous study we validated replicative senescence, a model of cell senescence that permits the study of cells as they progress to senescence, in human coronary artery endothelial cells (HCAEC). Here, we tested the hypothesis that senescent endothelial cells, which accumulate with aging and release senescence‐associated secretory phenotype (SASP) and extracellular vesicles, create a pro‐inflammatory environment that adversely affects the viability and morphology of neurons, which are endpoints implicated in AD. We categorized the phenotypes of HCAEC by passage number and identified them as EP‐ early passage (non‐senescent), ES‐ early senescence and LS‐ late senescence. HCAEC at these varying stages of senescence were co‐cultured with LUHMES cells, a human neuronal cell line. Co‐culturing HCAEC LS with LUHMES significantly decreased LUHMES viability, while co‐culturing HCAEC ES with LUHMES decreased the number of neurites extended by LUHMES in 24h and decreased the length of LUHMES’ neurites in 48h, when compared to LUHMES grown in the absence of HCAEC for the same period of time. HCAEC EP or LS co‐cultured with LUHMES did not affect the number or length of the LUHMES’ neurites, when compared to LUHMES grown in the absence of HCAEC. Using a cytokine array containing probes for 105 analytes, we detected 17 inflammatory mediators released by the co‐cultures of HCAEC (EP, ES and LS) with LUHMES. Of these 17 mediators, 14 were also found at supernatants of HCAEC (EP, ES and LS) grown in the absence of LUHMES, and none of the analytes were detected in supernatants from LUHMES grown in the absence of HCAEC. Statistical analysis of the intensity of the positive reaction for inflammatory mediators in the array was run for all the 17 positive analytes, and only IL‐8 and Serpin E1 release into the supernatants of the co‐cultures were significantly increased in co‐cultures of LUHMES and senescent HCAEC (ES or LS), when compared to the levels of the same mediators released by co‐cultures of LUHMES and EP HCAEC. However, exposing LUHMES to IL‐8 and Serpin E1, in the absence of HCAEC, did not affect LUHMES viability, the number or length of LUHMES’ neurites or LUHMES’ NF‐kB activation. The results from the LUHMES and HCAEC co‐cultures study supports a role for aging endothelial cells in the toxicity and morphological remodeling of the surrounding neurons, which may contribute to the development and progression of neurodegenerative diseases. However, our data exclude IL‐8 and Serpin E1 as direct independent mediators of senescent HCAEC on neuronal cytotoxicity and neurite remodeling.

  PublisherDOI

• Aging Human Endothelial Cells Affect Neuronal Viability and Function

  The FASEB Journal · 2021-05-01

  article

  It is estimated that more than 50% of adults over 80 will develop dementia, including Alzheimer's disease (AD), and the primary risk factor for dementia is aging. Aging provides the substrate for neurodegenerative disease through increased inflammation and cellular dysfunction. Despite the fact that aging is a key risk factor in neurodegenerative disease, preclinical studies frequently model age‐related diseases using young rodents. In this study we used replicative senescence , a standard model of cell senescence that permits the study of cells as they progress to senescence to examine the differential effects of senescent vs. non‐senescent primary human endothelial cells on a human neuronal cell line. We hypothesize that senescent (Sen) endothelial cells (ECs), which accumulate with aging, create a pro‐inflammatory environment that adversely affects viability and function of neurons. First, we validated the replicative senescence process in human‐derived ECs by quantifying β‐galactosidase activity, a marker for cellular senescence, and the protein expression of Lamin B1, which decreases with senescence. After determining senescence phenotypes by passage number, ECs at varying stages of cellular senescence (EP: early passage, ES: early senescence, LS: late senescence) were co‐cultured with LUHMES (Lund Human Mesencephalic cell line ‐ dopamine‐like neurons) to assess neuronal cell viability by measuring release of lactate dehydrogenase (LDH) into the culture medium and neurite outgrowth. Nitric oxide and extracellular vesicles released into the culture medium were also evaluated as indicators of an inflammatory environment. Co‐culturing ECs with LUHMES decreased LUHMES cell viability as evidenced by an increase in LDH in co‐cultures of LUHMES LS EC and by a decreased number of nuclei in LUHMES co‐cultured with any of the EC types (EP, ES, LS). Co‐culture with any of the EC types increased the area labeled by MAP2 and phospho‐Neurofilament in LUHMES at 24h, indicating increased neurite outgrowth. At 48h, increased neurite outgrowth was observed in LUHMES+EP ECs and LUHMES+ES ECs co‐cultures but not in the LUHMES + LP ECs. Nitric oxide was not increased by co‐culture of LUHMES with any of the EC subtypes. The amount of extracellular vesicles as quantified by measuring the activity of acetylcholinesterase (AChE) was increased in co‐cultures compared to LUHMES controls, but did not significantly differ from EC controls. In summary, ES ECs promote neurite outgrowth whereas LS ECs promote neurodegeneration. These findings suggest the importance of EC aging on neuronal cell morphology and viability, both parameters affected in age‐related dementia, including Alzheimer's disease.

  PublisherDOI

• Cardiac Myocyte Z-Line Calmodulin Is Mainly RyR2-Bound, and Reduction Is Arrhythmogenic and Occurs in Heart Failure

  UNC Libraries · 2020-11-01 · 2 citations

  articleOpen accessSenior author

  Calmodulin (CaM) associates with cardiac ryanodine receptors (RyR2) as an important regulator. Defective CaM-RyR2 interaction may occur in heart failure (HF), cardiac hypertrophy, and catecholaminergic polymorphic ventricular tachycardia (CPVT). However, the in situ binding properties for CaM-RyR2 are unknown.

  PublisherDOI

• Exosomes in disease and regeneration: biological functions, diagnostics, and beneficial effects

  AJP Heart and Circulatory Physiology · 2020 · 64 citations

  Senior authorCorresponding
  • Cell biology
  • Biology
  • Biochemistry

  Exosomes are a subtype of extracellular vesicles. They range from 30 to 150 nm in diameter and originate from intraluminal vesicles. Exosomes were first identified as the mechanism for releasing unnecessary molecules from reticulocytes as they matured to red blood cells. Since then, exosomes have been shown to be secreted by a broad spectrum of cells and play an important role in the cardiovascular system. Different stimuli are associated with increased exosome release and result in different exosome content. The release of harmful DNA and other molecules via exosomes has been proposed as a mechanism to maintain cellular homeostasis. Because exosomes contain parent cell-specific proteins on the membrane and in the cargo that is delivered to recipient cells, exosomes are potential diagnostic biomarkers of various types of diseases, including cardiovascular disease. As exosomes are readily taken up by other cells, stem cell-derived exosomes have been recognized as a potential cell-free regenerative therapy to repair not only the injured heart but other tissues as well. The objective of this review is to provide an overview of the biological functions of exosomes in heart disease and tissue regeneration. Therefore, state-of-the-art methods for exosome isolation and characterization, as well as approaches to assess exosome functional properties, are reviewed. Investigation of exosomes provides a new approach to the study of disease and biological processes. Exosomes provide a potential "liquid biopsy," as they are present in most, if not all, biological fluids that are released by a wide range of cell types.

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• Effects of N-Acetylcysteine and N-Acetylcysteine Amide on Erythrocyte Deformability and Oxidative Stress in a Rat Model of Lower Extremity Ischemia-Reperfusion Injury

  Cardiology Research and Practice · 2020-09-29 · 15 citations

  articleOpen accessSenior author

  N-acetylcysteine (NAC) is an antioxidant which works as a free radical scavenger and antiapoptotic agent. N-acetylcysteine-amide (NACA) is a modified form of NAC containing an amide group instead of a carboxyl group of NAC. Our study aims to investigate the effectiveness of these two substances on erythrocyte deformability and oxidative stress in muscle tissue. Materials and Methods. A total of 24 Wistar albino rats were used in our study. The animals were randomly divided into five groups as control (n: 6), ischemia (n: 6), NAC (n: 6), and NACA (n: 6). In the ischemia, NAC, and NACA groups, 120 min of ischemia and 120 min of reperfusion were achieved by placing nontraumatic vascular clamps across the abdominal aorta. The NAC and NACA groups were administered an injection 30 min before ischemia (100 mg/kg NAC; 100 mg/kg NACA; intravenous). Blood samples were taken from the animals at the end of the ischemic period. The lower extremity gastrocnemius muscle was isolated and stored at −80 degrees to assess the total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) values and was analyzed. Results. The erythrocyte deformability index was found to be statistically significantly lower in rats treated with NAC and NACA before ischemia-reperfusion compared to the groups that received only ischemia-reperfusion. In addition, no statistically significant difference was found between the control group and the NAC and NACA groups. The groups receiving NAC and NACA before ischemia exhibited higher total antioxidative status and lower total oxidative status while the oxidative stress index was also lower. Conclusion. The results of our study demonstrated the protective effects of NAC and NACA on erythrocyte deformability and oxidative damage in skeletal muscle in lower extremity ischemia-reperfusion. NAC and NACA exhibited similar protective effects on oxidative damage and erythrocyte deformability.

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• Heat shock protein 60 and cardiovascular diseases: An intricate love‐hate story

  Medicinal Research Reviews · 2020 · 54 citations

  • Immunology
  • Biology
  • Medicine

  Cardiovascular diseases (CVDs) are the result of complex pathophysiological processes in the tissues comprising the heart and blood vessels. Inflammation is the main culprit for the development of cardiovascular dysfunction, and it may be traced to cellular stress events including apoptosis, oxidative and shear stress, and cellular and humoral immune responses, all of which impair the system's structure and function. An intracellular chaperone, heat shock protein 60 (HSP60) is an intriguing example of a protein that may both be an ally and a foe for cardiovascular homeostasis; on one hand providing protection against cellular injury, and on the other triggering damaging responses through innate and adaptive immunity. In this review we will discuss the functions of HSP60 and its effects on cells and the immune system regulation, only to later address its implications in the development and progression of CVD. Lastly, we summarize the outcome of various studies targeting HSP60 as a potential therapeutic strategy for cardiovascular and other diseases.

  PublisherOA PDFDOI

Frequent coauthors

• Nipavan Chiamvimonvat

  University of California, Davis

  58 shared

• James P. Stice

  46 shared

• Le Chen

  39 shared

• Sanjiv Gupta

  30 shared

• Valeriy Timofeyev

  University of California, Davis

  30 shared

• Se-Chan Kim

  University of Bonn

  30 shared

• Georg Baumgarten

  Johanniter-Krankenhaus Bonn

  28 shared

• Ling Lü

  Nanjing Normal University

  28 shared

Education

• M.D.

  Yale School of Medicine

  1979

• AB magna cum laude, Biology

  Harvard University

  1974