Allan L. Harrelson

Proinflammatory phenotype of perivascular adipocytes: influence of high-fat feeding.

Adipose tissue depots originate from distinct precursor cells, are functionally diverse, and modulate disease processes in a depot-specific manner. However, the functional properties of perivascular adipocytes, and their influence on disease of the blood vessel wall, remain to be determined. We show that human coronary perivascular adipocytes exhibit a reduced state of adipocytic differentiation as compared with adipocytes derived from subcutaneous and visceral (perirenal) adipose depots. Secretion of antiinflammatory adiponectin is markedly reduced, whereas that of proinflammatory cytokines interleukin-6, interleukin-8, and monocyte chemoattractant protein-1, is markedly increased in perivascular adipocytes. These depot-specific differences in adipocyte function are demonstrable in both freshly isolated adipose tissues and in vitro–differentiated adipocytes. Murine aortic arch perivascular adipose tissues likewise express lower levels of adipocyte-associated genes as compared with subcutaneous and visceral adipose tissues. Moreover, 2 weeks of high-fat feeding caused further reductions in adipocyte-associated gene expression, while upregulating proinflammatory gene expression, in perivascular adipose tissues. These changes were observed in the absence of macrophage recruitment to the perivascular adipose depot. We conclude that perivascular adipocytes exhibit reduced differentiation and a heightened proinflammatory state, properties that are intrinsic to the adipocytes residing in this depot. Dysfunction of perivascular adipose tissue induced by fat feeding suggests that this unique adipose depot is capable of linking metabolic signals to inflammation in the blood vessel wall.

Dependence of liver-specific transcription on tissue organization.

When the liver is disaggregated and hepatocytes are cultured as a cellular monolayer for 24 h, a sharp decline (80 to 99% decrease) in the transcription of most liver-specific mRNAs, but not common mRNAs, occurs (Clayton and Darnell, Mol. Cell. Biol. 2:1552-1561, 1983). A wide variety of culture conditions involving various hormones and substrates and cocultivation with other cells failed to sustain high rates of liver-specific mRNA synthesis in cultured hepatocytes, although they continued to synthesize common mRNAs at normal or elevated rates. In contrast, when slices of intact mouse liver tissue were placed in culture, the transcription of liver-specific genes was maintained at high levels (20 to 100% of normal liver). Furthermore, we found that cells in the liver could be disengaged and immediately reengaged in a tissue-like structure by perfusing the liver with EDTA followed by serum-containing culture medium. Slices of reengaged liver continued to transcribe tissue-specific mRNA sequences at significantly higher rates after 24 h in culture than did individual cells isolated by EDTA perfusion followed by culturing as a monolayer. Therefore we conclude that a mature tissue structure plays an important role in the maintenance of maximum tissue-specific transcription in liver cells.

Regulation of Endotoxin-Induced Proinflammatory Activation in Human Coronary Artery Cells: Expression of Functional Membrane-Bound CD14 by Human Coronary Artery Smooth Muscle Cells

Low-level endotoxemia has been identified as a powerful risk factor for atherosclerosis. However, little is known about the mechanisms that regulate endotoxin responsiveness in vascular cells. We conducted experiments to compare the relative responses of human coronary artery endothelial cells (HCAEC) and smooth muscle cells (HCASMC) to very low levels of endotoxin, and to elucidate the mechanisms that regulate endotoxin responsiveness in vascular cells. Endotoxin (≤1 ng/ml) caused production of chemotactic cytokines in HCAEC. Endotoxin-induced cytokine production was maximal at LPS-binding protein:soluble CD14 ratios <1, typically observed in individuals with subclinical infection; higher LPS-binding protein:soluble CD14 ratios were inhibitory. Endotoxin potently activated HCASMC, with cytokine release >10-fold higher in magnitude at >10-fold lower threshold concentrations (10–30 pg/ml) compared with HCAEC. This remarkable sensitivity of HCASMC to very low endotoxin concentrations, comparable to that found in circulating monocytes, was not due to differential expression of TLR4, which was detected in HCAEC, HCASMC, and intact coronary arteries. Surprisingly, membrane-bound CD14 was detected in seven different lines of HCASMC, conferring responsiveness to endotoxin and to lipoteichoic acid, a product of Gram-positive bacteria, in these cells. These results suggest that the low levels of endotoxin associated with increased risk for atherosclerosis are sufficient to produce inflammatory responses in coronary artery cells. Because CD14 recognizes a diverse array of inflammatory mediators and functions as a pattern recognition molecule in inflammatory cells, expression of membrane-bound CD14 in HCASMC implies a potentially broader role for these cells in transducing innate immune responses in the vasculature.

Adrenocortical steroids modify neurotransmitter-stimulated cyclic AMP accumulation in the hippocampus and limbic brain of the rat

Abstract: Glucocorticoid hormones are known to affect limbic system structures that have high levels of specific receptors for glucocorticoids, especially the hippocampus (HIPP). To understand how glucocorticoids may affect syn‐aptic transmission, we have tested the effects of adrenal removal and glucocorticoid replacement on neurotransmit‐ter‐stimulated cyclic AMP accumulation in brain slices from the rat limbic system. Adrenalectomy (ADX) caused an enhancement of vasoactive intestinal peptide (VIP)‐stimulated cyclic AMP accumulation in HIPP, amygdala (AMYG), and septum (SEP). In HIPP, ADX increased the cyclic AMP response to isoproterenol (ISOP) and decreased the response to histamine (HIST). In the AMYG and SEP, ADX did not affect significantly the action of ISOP, but ADX did decrease the response to HIST in AMYG. Administration of dexamethasone or corticosterone reversed the effects of ADX on cyclic AMP accumulation in the HIPP. The dexamethasone action on VIP‐stimulated cyclic AMP accumulation takes place within 48 h and is most apparent in the mid‐range of the VIP dose‐response curve. These results demonstrate that glucocorticoids regulate neurotrans‐mitter‐stimulated cyclic AMP generation in a fashion that is specific, both for the neurotransmitter involved and for the brain regions affected.

Steroid Hormone Influences on Cyclic AMP-Generating Systems

Publisher Summary This chapter reviews the evidence that steroids influence the activity of the cyclic adenosine monophosphate (cAMP)-generating system and describes the structure and function of adenylate cyclase. Steroid hormones, especially glucocorticoids, have profound effects on the biochemistry of liver and fat tissues, and steroid regulation of cAMP metabolism in cells derived from liver and adipose tissues has been known for some time. Adrenalectomy also makes the liver refractory to cAMP-induced glycogenolysis and gluconeogenesis, whereas glucocorticoid replacement allows intracellular cAMP to once again stimulate glucose metabolism. Although regulation of cAMP levels by glucocorticoids in adipocytes differs in some ways from that in the liver, the general story is very much the same––namely, effects at both the level of cAMP and in postadenylate cyclase, cAMP-dependent biochemical phenomena. However, steroid regulation differs somewhat among the tissues, in that adrenalectomy has a biphasic effect on adenylate cyclase in adipose tissue, with an initial increase followed by a long-term decrease.

Personalized echocardiography: clinical applications of advanced echocardiography and future directions

Future cardiology practice will be increasingly individualized, and thus to maintain its central role, echocardiography must keep pushing to expand the boundaries of real-time data acquisition from tissue and fluid motion, and yet still provide efficient and timely data analysis that leads to succinct, clear clinical recommendations tailored to each person in our care. In this article, recent efforts to expand echocardiography techniques into an era of increasingly personalized cardiology, including advances in color-coded tissue Doppler, 3D echocardiography and complex exercise stress echocardiography are described. The common metric for success in each of these efforts is the development of robust and institutionally supportable echocardiography protocols for specific cardiology disease populations that currently may be underdiagnosed and/or undertreated. The common result in each case should be the creation of new guidelines that can supplement the current standard protocols advocated by professional echocardiography organizations.

Left Ventricular Volume with Three‐Dimensional Echocardiography: All Vendors the Same?

To the Editor: As Anwar et al. nicely reviewed in your journal,1 three-dimensional (3D) echocardiography has been utilized to measure left ventricular (LV) volumes, particularly for the management of patients with heart failure, and our knowledge on clinical implications of this has been rapidly expanding.2 Several vendors released the commercially available software to yield 3D LV volume calculations in a last few years and it is now popular that more than one vendor 3D LV volume software are used for both clinical and research purposes even in the same institute. However, the authors1 have not discussed the important fact that no published information is available on cross-platform comparisons of current LV volume software, which we believe is critical to acknowledge. In our opinion, at least such comparisons at individual echocardiography laboratory will help to further strengthen verification of LV volume calculation with 3D echocardiography in the era of its wide use. In this communication, we would like to inform the readers that we compared 3D LV volumes calculated by Q Lab (Philips Inc., Bothell, WA, USA) with those by TomTec 4D analysis (TomTec Inc., Unterscheissheim, Germany) to address this issue. 3D LV volumes were calculated from the same datasets acquired by full-volume 3D echocardiography using the iE33 ultrasound system (Philips Inc.) in 16 consecutive patients who came to our hospital for an evaluation with 3D echocardiography. The range of 2D LV ejection fraction was 28–72% in this group. A single blinded experienced echocardiographer analyzed the data. Our analysis showed that both 3D LV enddiastolic and end-systolic volumes measured showed a tight correlation among the vendors (r2 = 0.989, P < 0.01; r2 = 0.993, P < 0.01, respectively). The mean of difference3 was 6.9 ± 6.1 mL for LV end-diastolic volume and 4.9 ± 4.1 mL for LV end-systolic volume. The percent error3 was 2.8 ± 2.0% for LV end-diastolic volume and 4.5 ± 3.3% for LV end-systolic volume. In our data, 3D LV volumes are calculated similarly between the two vendor software tested. Our data further complement clinical validation of measuring 3D LV volumes which is discussed in the previous review.1 We would like to emphasize the importance of critical evaluation of new 3D echocardiography technology for its widespread use from our experience.

Customized exercise echocardiography: beyond detection of coronary artery disease.

Exercise echocardiography has been established as a reliable diagnostic tool for assessment of myocardial ischemia. However, more recent advances in its technique have expanded its routine clinical use to include quantification of exercise‐induced diastolic dysfunction, exercise‐induced pulmonary hypertension, and dynamic assessment of mitral and aortic valve function. The indications for exercise echocardiography have increased to include cardiac symptoms such as exertional dyspnea, fatigue, and limited exercise capacity. In light of its expanded capability for evaluating cardiovascular function, we believe that exercise echocardiography should be utilized in a new paradigm of personalized cardiology, in which we regularly investigate individual patient symptoms for endpoints beyond critical myocardial ischemia, for example, exercise‐induced pulmonary hypertension. We refer to this refocused use of exercise echocardiography as “customized exercise echocardiography.” In this review article, we present current scientific evidence to support our proposed role and discuss the logistical requirements for proper test performance of customized exercise echocardiography. (Echocardiography 2010;27:186‐194)