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C Patterson

Publications and source records attributed to C Patterson.

At least 37 records · Page 2Linked to original sources
PubMed2001

Thrombin regulates vascular smooth muscle cell growth and heat shock proteins via the JAK-STAT pathway.

The growth-stimulating effects of thrombin are mediated primarily via activation of a G protein-coupled receptor, PAR-1. Because PAR-1 has no intrinsic tyrosine kinase activity, yet requires tyrosine phosphorylation events to induce mitogenesis, we investigated the role of the Janus tyrosine kinases (JAKs) in thrombin-mediated signaling. JAK2 was activated rapidly in rat vascular smooth muscle cells (VSMC) treated with thrombin, and signal transducers and activators of transcription (STAT1 and STAT3) were phosphorylated and translocated to the nucleus in a JAK2-dependent manner. AG-490, a JAK2-specific inhibitor, and a dominant negative JAK2 mutant inhibited thrombin-induced ERK2 activity and VSMC proliferation suggesting that JAK2 is upstream of the Ras/Raf/MEK/ERK pathway. To elucidate the functional significance of JAK-STAT activation, we studied the effect of thrombin on heat shock protein (Hsp) expression, based upon the following: 1) reports that thrombin stimulates reactive oxygen species production in VSMC; 2) the putative role of Hsps in modulating cellular responses to reactive oxygen species; and 3) the presence of functional STAT1/3-binding sites in Hsp70 and Hsp90beta promoters. Indeed, thrombin up-regulated Hsp70 and Hsp90 protein expression via enhanced binding of STATs to cognate binding sites in the Hsp70 and Hsp90 promoters. Together, these results suggest that JAK-STAT pathway activation is necessary for thrombin-induced VSMC growth and Hsp gene expression.

Animals↗
PubMed2001

[Current topics in vascular biology: an update for the 21st century].

Although taken for granted in the present day, the central role played by the blood vessels themselves in regulating the cardiovascular system under physiologic and pathologic conditions has only been understood in the last several decades. The field of vascular biology grew out of this appreciation of the primacy of the vasculature in cardiovascular pathologies. In this review, we come up to date on several topics of particular interest to the field of vascular biology as it enters the 21st century: namely, the role of oxidative stress in vascular function and dysfunction; angiogenesis and angiogenic gene therapies; and emerging biomarkers of atherosclerosis. Each of these areas is likely to experience significant advances in the coming years that will directly impact clinical decision-making and care of patients with cardiovascular diseases.

Blood Vessels↗
PubMed2001

The recognition, assessment and management of dementing disorders: conclusions from the Canadian Consensus Conference on Dementia.

OBJECTIVE: i) To develop evidence based consensus statements on which to build clinical practice guidelines for primary care physicians towards the recognition, assessment and management of dementing disorders; ii) to disseminate and evaluate the impact of these statements and guidelines built on these statements. OPTIONS: Structured approach to assessment, including recommended laboratory tests, choices for neuroimaging and referral; management of complications (especially behaviour problems and depression) and use of cognitive enhancing agents. POTENTIAL OUTCOMES: Consistent and improved clinical care of persons with dementia; cost containment by more selective use of laboratory investigations, neuroimaging and referrals; appropriate use of cognitive enhancing agents. EVIDENCE: Authors of each background paper were entrusted to: perform a literature search, discover additional relevant material including references cited in retrieved articles; consult with other experts in the field and then synthesize information. Standard rules of evidence were applied. Based upon this evidence, consensus statements were developed by a group of experts, guided by a steering committee of eight individuals from the areas of Neurology, Geriatric Medicine, Psychiatry, Family Medicine, Preventive Health Care and Health Care Systems. VALUES: Recommendations have been developed with particular attention to the context of primary care and are intended to support family physicians in their ongoing assessment and care of patients with dementia. BENEFITS, HARMS AND COSTS: Potential for improved clinical care of individuals with dementia. A dissemination and evaluation strategy will attempt to measure the impact of the recommendations. RECOMMENDATIONS: See text. VALIDATION: Four other sets of consensus statements and/or guidelines have been published recently. These recommendations are generally congruent with our own consensus statements. The consensus statements have been endorsed by relevant bodies in Canada.

Aged↗
PubMed2001

Preventing dementia.

Primary prevention will become increasingly important as dementia prevalence increases and effective retardive therapies are developed. To date, only one randomized controlled trial (involving treatment of systolic hypertension) has demonstrated that the incidence of dementia can be reduced. Physicians should remain alert to possible secondary causes of dementia and correct these whenever possible. Primary and secondary prevention of stroke should reduce dementia related to cerebrovascular disease either directly or as a comorbid factor in Alzheimer's disease (AD). Epidemiological studies have revealed a number of risk factors for AD including genetic mutation, susceptibility genes, positive family history, Down's syndrome, age, sex, years of education, head trauma and neurotoxins. In case-control studies non-steroidal anti-inflammatory medication and estrogen replacement therapy appear to decrease the relative risk of developing AD. Further research to develop and test preventative therapies in AD and other dementias should be strongly encouraged.

Aged↗
PubMed2001

The Hsc70 co-chaperone CHIP targets immature CFTR for proteasomal degradation.

The folding of both wild-type and mutant forms of the cystic-fibrosis transmembrane-conductance regulator (CFTR), a plasma-membrane chloride-ion channel, is inefficient. Most nascent CFTR is retained in the endoplasmic reticulum and degraded by the ubiquitin proteasome pathway. Aberrant folding and defective trafficking of CFTRDeltaF508 is the principal cause of cystic fibrosis, but how the endoplasmic-reticulum quality-control system targets CFTR for degradation remains unknown. CHIP is a cytosolic U-box protein that interacts with Hsc70 through a set of tetratricorepeat motifs. The U-box represents a modified form of the ring-finger motif that is found in ubiquitin ligases and that defines the E4 family of polyubiquitination factors. Here we show that CHIP functions with Hsc70 to sense the folded state of CFTR and targets aberrant forms for proteasomal degradation by promoting their ubiquitination. The U-box appeared essential for this process because overexpresion of CHIPDeltaU-box inhibited the action of endogenous CHIP and blocked CFTR ubiquitination and degradation. CHIP is a co-chaperone that converts Hsc70 from a protein-folding machine into a degradation factor that functions in endoplasmic-reticulum quality control.

Animals↗
PubMed2001

The co-chaperone CHIP regulates protein triage decisions mediated by heat-shock proteins.

To maintain quality control in cells, mechanisms distinguish among improperly folded peptides, mature and functional proteins, and proteins to be targeted for degradation. The molecular chaperones, including heat-shock protein Hsp90, have the ability to recognize misfolded proteins and assist in their conversion to a functional conformation. Disruption of Hsp90 heterocomplexes by the Hsp90 inhibitor geldanamycin leads to substrate degradation through the ubiquitin-proteasome pathway, implicating this system in protein triage decisions. We previously identified CHIP (carboxyl terminus of Hsc70-interacting protein) to be an interaction partner of Hsc70 (ref. 4). CHIP also interacts directly with a tetratricopeptide repeat acceptor site of Hsp90, incorporating into Hsp90 heterocomplexes and eliciting release of the regulatory cofactor p23. Here we show that CHIP abolishes the steroid-binding activity and transactivation potential of the glucocorticoid receptor, a well-characterized Hsp90 substrate, even though it has little effect on its synthesis. Instead, CHIP induces ubiquitylation of the glucocorticoid receptor and degradation through the proteasome. By remodelling Hsp90 heterocomplexes to favour substrate degradation, CHIP modulates protein triage decisions that regulate the balance between protein folding and degradation for chaperone substrates.

Animals↗
PubMed2001

Selenium levels in cow's milk from different regions of Australia.

Homogenised cow's milk samples were collected each season in 1990 and 1991 from 19 selected dairy factories in different regions across Australia. Fresh cow's milk samples were also collected every month in 1990 and 1991 from 24 selected dairy farms in Queensland. Selenium (Se) analyses were performed by spectrofluorimetry after complexing with 2,3-diaminonaphthalene. The study found a wide variation of Se levels in homogenised milk from dairy milk factories. Statistical analysis using unpaired t-test showed that Se levels in summer were significantly higher (P < 0.001) than in other seasons. Mean concentrations in summer, autumn, winter and spring for 1990 and 1991 were 23.8 +/- 4.6, 20.9 +/- 4.4, 20.7 +/- 4.2 and 20.6 +/- 4.8 micrograms/L, respectively. A two-way ANOVA analysis also indicated that regions and season have a significant influence (P < 0.001) on Se levels and that there is an interaction between regions and seasons. High Se levels in each region tend to be associated with high Se levels in summer milk. A wide variation of Se levels was also found in raw milk collected from dairy farms. Mean concentration was 22.0 +/- 6.0 micrograms/L, with a range of 6.7 to 47.6 micrograms/L. When the values of Se levels in homogenised milk for each season were used to estimate the contribution of milk to daily intake of different populations groups, it was found that infants have the highest intake (10.0-12.2 micrograms/day) which meets the Australian Recommended Dietary Intake.

Analysis of Variance↗
PubMed2001

From the cradle to the grave: molecular chaperones that may choose between folding and degradation.

Molecular chaperones are known to facilitate cellular protein folding. They bind non-native proteins and orchestrate the folding process in conjunction with regulatory cofactors that modulate the affinity of the chaperone for its substrate. However, not every attempt to fold a protein is successful and chaperones can direct misfolded proteins to the cellular degradation machinery for destruction. Protein quality control thus appears to involve close cooperation between molecular chaperones and energy-dependent proteases. Molecular mechanisms underlying this interplay have been largely enigmatic so far. Here we present a novel concept for the regulation of the eukaryotic Hsp70 and Hsp90 chaperone systems during protein folding and protein degradation.

Animals↗
PubMed2001

Shear stress reduces protease activated receptor-1 expression in human endothelial cells.

Shear stress has been shown to regulate several genes involved in the thrombotic and proliferative functions of endothelial cells. Thrombin receptor (protease-activated receptor-1: PAR-1) increases at sites of vascular injury, which suggests an important role for PAR-1 in vascular diseases. However, the effect of shear stress on PAR-1 expression has not been previously studied. This work investigates effects of shear stress on PAR-1 gene expression in both human umbilical vein endothelial cells (HUVECs) and microvascular endothelial cells (HMECs). Cells were exposed to different shear stresses using a parallel plate flow system. Northern blot and flow cytometry analysis showed that shear stress down-regulated PAR-1 messenger RNA (mRNA) and protein levels in both HUVECs and HMECs but with different thresholds. Furthermore, shear-reduced PAR-1 mRNA was due to a decrease of transcription rate, not increased mRNA degradation. Postshear stress release of endothelin-1 in response to thrombin was reduced in HUVECs and HMECs. Moreover, inhibitors of potential signaling pathways applied during shear stress indicated mediation of the shear-decreased PAR-1 expression by protein kinases. In conclusion, shear stress exposure reduces PAR-1 gene expression in HMECs and HUVECs through a mechanism dependent in part on protein kinases, leading to altered endothelial cell functional responses to thrombin.

Biomedical Engineering↗
PubMed2001

Roles for the Rhodobacter sphaeroides CcmA and CcmG proteins.

Rhodobacter sphaeroides cells containing an in-frame deletion within ccmA lack detectable soluble and membrane-bound c-type cytochromes and are unable to grow under conditions where these proteins are required. Only strains merodiploid for ccmABCDG were found after attempting to generate cells containing either a ccmG null mutation or a ccmA allele that should be polar on to expression of ccmBCDG, suggesting that CcmG has another important role in R. sphaeroides.

Bacterial Outer Membrane Proteins↗
PubMed2001

Peroxynitrite causes endothelial cell monolayer barrier dysfunction.

Nitric oxide (.NO) attenuates hydrogen peroxide (H(2)O(2))-mediated barrier dysfunction in cultured porcine pulmonary artery endothelial cells (PAEC) (Gupta MP, Ober MD, Patterson C, Al-Hassani M, Natarajan V, and Hart, CM. Am J Physiol Lung Cell Mol Physiol 280: L116-L126, 2001). However,.NO rapidly combines with superoxide (O) to form the powerful oxidant peroxynitrite (ONOO(-)), which we hypothesized would cause PAEC monolayer barrier dysfunction. To test this hypothesis, we treated PAEC with ONOO(-) (500 microM) or 3-morpholinosydnonimine hydrochloride (SIN-1; 1-500 microM). SIN-1-mediated ONOO(-) formation was confirmed by monitoring the oxidation of dihydrorhodamine 123 to rhodamine. Both ONOO(-) and SIN-1 increased albumin clearance (P < 0.05) in the absence of cytotoxicity and altered the architecture of the cytoskeletal proteins actin and beta-catenin as detected by immunofluorescent confocal imaging. ONOO(-)-induced barrier dysfunction was partially reversible and was attenuated by cysteine. Both ONOO(-) and SIN-1 nitrated tyrosine residues, including those on beta-catenin and actin, and oxidized proteins in PAEC. The introduction of actin treated with ONOO(-) into PAEC monolayers via liposomes also resulted in barrier dysfunction. These results indicate that ONOO(-) directly alters endothelial cytoskeletal proteins, leading to barrier dysfunction.

Actins↗
PubMed2001

Aging, oxidative responses, and proliferative capacity in cultured mouse aortic smooth muscle cells.

The cellular mechanisms that contribute to the acceleration of atherosclerosis in aging populations are poorly understood, although it is hypothesized that changes in the proliferative capacity of vascular smooth muscle cells is contributory. We addressed the relationship among aging, generation of reactive oxygen species (ROS), and proliferation in primary culture smooth muscle cells (SMC) derived from the aortas of young (4 mo old) and aged (16 mo old) mice to understand the phenotypic modulation of these cells as aging occurs. SMC from aged mice had decreased proliferative capacity in response to alpha-thrombin stimulation, yet generated higher levels of ROS and had constitutively increased mitogen-activated protein kinase activity, in comparison with cells from younger mice. These effects may be explained by dysregulation of cell cycle-associated proteins such as cyclin D1 and p27Kip1 in SMC from aged mice. Increased ROS generation was associated with decreased endogenous antioxidant activity, increased lipid peroxidation, and mitochondrial DNA damage. Accrual of oxidant-induced damage and decreased proliferative capacity in SMC may explain, in part, the age-associated transition to plaque instability in humans with atherosclerosis.

Aging↗
PubMed2001

PTP-epsilon, a tyrosine phosphatase expressed in endothelium, negatively regulates endothelial cell proliferation.

The vascular endothelium is a dynamic interface between the blood vessel and circulating factors and, as such, plays a critical role in vascular events like inflammation, angiogenesis, and hemostasis. Whereas specific protein tyrosine kinases have been identified in these processes, less is known about their protein tyrosine phosphatase (PTP) counterparts. We utilized a RT-PCR/differential hybridization assay to identify PTP-epsilon as a highly abundant endothelial cell PTP. PTP-epsilon mRNA expression is growth factor responsive, suggesting a role for this enzyme in endothelial cell proliferation. Overexpression of PTP-epsilon decreases proliferation by 60% in human umbilical vein endothelial cells (HUVEC) but not in smooth muscle cells or fibroblasts. In contrast, overexpression of PTP-epsilon (D284A), a catalytically inactive mutant, has no significant effect on HUVEC proliferation. These data provide the first functional characterization of PTP-epsilon in endothelial cells and identify a novel pathway that negatively regulates endothelial cell growth. Such a pathway may have important implications in vascular development and angiogenesis.

Blood Physiological Phenomena↗
PubMed2001

Nitric oxide attenuates H(2)O(2)-induced endothelial barrier dysfunction: mechanisms of protection.

Nitric oxide (.NO) attenuates hydrogen peroxide (H(2)O(2))-mediated injury in porcine pulmonary artery endothelial cells (PAECs) and modulates intracellular levels of cGMP and cAMP. We hypothesized that.NO attenuates H(2)O(2)-induced PAEC monolayer barrier dysfunction through cyclic nucleotide-dependent signaling mechanisms. To examine this hypothesis, cultured PAEC monolayers were treated with H(2)O(2), and barrier function was measured as transmonolayer albumin clearance. H(2)O(2) caused significant PAEC barrier dysfunction that was attenuated by intracellular as well as extracellular.NO generation.NO increased PAEC cGMP and cAMP levels, but treatment with inhibitors of soluble guanylate cyclase or protein kinase G did not abrogate.NO-mediated barrier protection. In contrast, H(2)O(2) decreased protein kinase A activity, and inhibiting protein kinase A abrogated the protective effect of.NO. H(2)O(2)-induced barrier dysfunction was not associated with decreased levels of cGMP or cAMP. 3-Isobutyl-1-methylxanthine and the cGMP analog 8-bromo-cGMP had little effect on H(2)O(2)-mediated endothelial barrier dysfunction, whereas 8-bromo-cAMP plus 3-isobutyl-1-methylxanthine was protective. These results indicate that.NO modulates vascular endothelial barrier function through cAMP-dependent signaling mechanisms.

1-Methyl-3-isobutylxanthine↗
PubMed2001

Reactive oxygen species regulate heat-shock protein 70 via the JAK/STAT pathway.

Reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) activate intracellular signal transduction pathways implicated in the pathogenesis of cardiovascular disease. H(2)O(2) is a mitogen for rat vascular smooth muscle cells (VSMCs), and protein tyrosine phosphorylation is a critical event in VSMC mitogenesis. Therefore, we investigated whether the mitogenic effects of H(2)O(2), such as stimulation of extracellular signal-regulated kinase (ERK)2, are mediated via activation of cytoplasmic Janus tyrosine kinases (JAKs). JAK2 was activated rapidly in VSMCs treated with H(2)O(2), and signal transducers and activators of transcription (STAT) STAT1 and STAT3 were tyrosine-phosphorylated and translocated to the nucleus in a JAK2-dependent manner. Inhibition of JAK2 activity with AG-490 partially inhibited H(2)O(2)-induced ERK2 activity, suggesting that JAK2 is upstream of the Ras/Raf/mitogen-activated protein kinase-ERK/ERK mitogenic pathway. Because heat-shock proteins (HSPs) can protect cells from ROS, we investigated the effect of H(2)O(2) on HSP expression. H(2)O(2) stimulated HSP70 expression in a time-dependent manner, and AG-490 abolished H(2)O(2)-induced HSP70 expression. H(2)O(2) activated the HSP70 promoter via enhanced binding of STATs to cognate binding sites in the promoter. Regulation of chaperones such as HSP70 via activation of the JAK/STAT pathway suggests that in addition to its growth-promoting effects, this pathway may help VSMCs adapt to oxidative stress.

Animals↗