Hypertension and increased endothelial mechanical stretch promote monocyte differentiation and activation: roles of STAT3, interleukin 6 and hydrogen peroxide

Aims: Monocytes play an important role in hypertension. Circulating monocytes in humans exist as classical, intermediate and non-classical forms. Monocyte differentiation can be influenced by the endothelium, which in turn is activated in hypertension by mechanical stretch. We sought to examine the role of increased endothelial stretch and hypertension on monocyte phenotype and function. Methods and Results: Human monocytes were cultured with confluent human aortic endothelial cells undergoing either 5% or 10% cyclical stretch. We also characterized circulating monocytes in normotensive and hypertensive humans. In addition, we quantified accumulation of activated monocytes and monocyte-derived cells in aortas and kidneys of mice with Angiotensin II-induced hypertension. Increased endothelial stretch enhanced monocyte conversion to CD14++CD16+ intermediate monocytes and monocytes bearing the CD209 marker and markedly stimulated monocyte mRNA expression of interleukin (IL)-6, IL-1β, IL-23, chemokine (C-C motif) ligand 4 and tumor necrosis factor α. STAT3 in monocytes was activated by increased endothelial stretch. Inhibition of STAT3, neutralization of IL-6 and scavenging of hydrogen peroxide prevented formation of intermediate monocytes in response to increased endothelial stretch. We also found evidence that nitric oxide inhibits formation of intermediate monocytes and STAT3 activation. In vivo studies demonstrated that humans with hypertension have increased intermediate and non-classical monocytes and that intermediate monocytes demonstrate evidence of STAT3 activation. Mice with experimental hypertension exhibit increased aortic and renal infiltration of monocytes, dendritic cells and macrophages with activated STAT3. Conclusions: These findings provide insight into how monocytes are activated by the vascular endothelium during hypertension. This is likely in part due to a loss of nitric oxide signaling and increased release of IL-6 and hydrogen peroxide by the dysfunctional endothelium and a parallel increase in STAT activation in adjacent monocytes. Interventions to enhance bioavailable nitric oxide, reduce IL-6 or hydrogen peroxide production or to inhibit STAT3 may have anti-inflammatory roles in hypertension and related conditions

Fluorescence-based classification of Caribbean coral reef organisms and substrates.

A diverse group of coral reef organisms, representing several phyla, possess fluorescent pigments. We investigated the potential of using the characteristic fluorescence emission spectra of these pigments to enable unsupervised, optical classification of coral reef habitats. We compiled a library of characteristic fluorescence spectra through in situ and laboratory measurements from a variety of specimens throughout the Caribbean. Because fluorescent pigments are not species-specific, the spectral library is organized in terms of 15 functional groups. We investigated the spectral separability of the functional groups in terms of the number of wavebands required to distinguish between them, using the similarity measures Spectral Angle Mapper (SAM), Spectral Information Divergence (SID), SID-SAM mixed measure, and Mahalanobis distance. This set of measures represents geometric, stochastic, joint geometric-stochastic, and statistical approaches to classifying spectra. Our hyperspectral fluorescence data were used to generate sets of 4-, 6-, and 8-waveband spectra, including random variations in relative signal amplitude, spectral peak shifts, and water-column attenuation. Each set consisted of 2 different band definitions: 'optimally-picked' and 'evenly-spaced.' The optimally-picked wavebands were chosen to coincide with as many peaks as possible in the functional group spectra. Reference libraries were formed from half of the spectra in each set and used for training purposes. Average classification accuracies ranged from 76.3% for SAM with 4 evenly-spaced wavebands to 93.8% for Mahalanobis distance with 8 evenly-spaced wavebands. The Mahalanobis distance consistently outperformed the other measures. In a second test, empirically-measured spectra were classified using the same reference libraries and the Mahalanobis distance for just the 8 evenly-spaced waveband case. Average classification accuracies were 84% and 87%, corresponding to the extremes in modeled water-column attenuation. The classification results from both tests indicate that a high degree of separability among the 15 fluorescent-spectra functional groups is possible using only a modest number of spectral bands

Fluorescence endmember library.

<p>Based on our measurements, most fluorescent signals observed on Caribbean reefs are attributable to one or more of these spectra.</p

Different spectral band sets used in the classification tests.

<p>Each band is designated by a center wavelength and half bandwidth, both in nm.</p

Fluorescence functional groups.

<p>These 15 spectra denote the most common fluorescent emissions we have measured on Caribbean reefs. Note: All of the stony coral functional groups (1–7) also include a chlorophyll component. Fluorescence intensities are plotted in arbitrary units, and the spectra indicate typical peak-to-peak ratios. The spectra also illustrate actual inter-functional-group differences. For example, corals with pigments 486 and 515 (group 4) tend to fluorescence ‘brighter’ than the other groups, and chlorophyll fluorescence in soft corals (group 8) is approximately 4 times more intense than that in green or brown algae (group 9). The spectra used in the classification comparisons included the effects of water-column attenuation and observed peak shifts, as described in the text.</p

Classification results for empirically-measured, fluorescence spectra.

<p>Water-column attenuation effects were applied for distances of 1 m and 3 m. Different numbers of example field spectra were used for each functional group. Example spectra from multiple genera were used for each group when possible. Erroneous classifications are indicated by the corresponding functional-group number. Asterisks denote groups for which classification success changed with increasing attenuation effects.</p

Classification results for <i>MAHAL</i>.

<p>Highlighted values indicate the minimum score for each band configuration.</p

Classification results for <i>SAM</i>.

<p>Highlighted values indicate the minimum score for each band configuration.</p

Functional groups and the pigment-mixing formulations used in the fluorescence model.

<p>Numbers indicate relative fluorescence-peak intensities. A value within the specified range was randomly chosen for each of the 10,000 synthesized spectra for each functional group.</p