Biomedical subjects

Timothy A Sutton

Publications and source records attributed to Timothy A Sutton.

6 recordsLinked to original sources

PubMed2006

Imaging vascular pathology.

Examining the mechanisms of renal microvascular alterations in disease and the ramifications they have for overall organ function has remained a challenge due to the complexity of the renal microvascular system and the inability to examine it with sufficient resolution in vivo. However, advances in intravital microscopy have provided opportunities to meet these challenges. In this review we will examine specific areas where intravital imaging has advanced our knowledge of renal disease processes and present areas where these techniques, especially intravital multiphoton microscopy, have even further potential to integrate our knowledge of renal vascular pathology.

Animals↗

PubMed2004

Minocycline reduces renal microvascular leakage in a rat model of ischemic renal injury.

Tetracyclines exhibit significant anti-inflammatory properties, inhibit matrix metalloproteinases (MMPs), and are protective in models of ischemia-reperfusion injury (IRI). Both inflammatory cascades and MMP activation have been demonstrated to modulate microvascular permeability. Because increased microvascular permeability occurs during IRI in a variety of organ systems including the kidney, we hypothesized that minocycline, a semisynthetic tetracycline, would diminish microvascular leakage during renal IRI. To test this hypothesis, we used intravital 2-photon microscopy to examine leakage of fluorescent dextrans from the vasculature in a rodent model of IRI. Minocycline significantly reduced the extent of dextran (500 kDa) leakage from the renal microvasculature 24 h after ischemia. Although minocycline diminished leukocyte accumulation in the kidney following ischemia, areas of leukocyte accumulation did not correlate with areas of microvascular permeability in either the saline- or minocycline-pretreated animals. Minocycline diminished the perivascular increase in MMP-2 and MMP-9, as well as the increase in MMP-2 activity 24 h after ischemia. ABT-518, a specific inhibitor of MMP-2 and MMP-9, also significantly reduced the extent of dextran (500 kDa) leakage from the renal microvasculature 24 h after ischemia. Our results indicate that minocycline mitigates the renal microvascular permeability defect following IRI. This effect is spatially distinct from the effect of minocycline on leukocyte accumulation and may be related to diminished activity of MMPs on the integrity of the perivascular matrix.

Acute Kidney Injury↗

PubMed2004

Endothelial injury and dysfunction: role in the extension phase of acute renal failure.

The pathophysiology of ischemic acute renal failure (ARF) involves a complex interplay between renal hemodynamics, tubular and endothelial cell injury, and inflammatory processes. A growing body of evidence supports the contribution of altered renal vascular function, especially at the microvascular level, in initiating and subsequently extending the initial tubular injury. The extension phase of ischemic ARF involves continued reduction in renal perfusion, ongoing hypoxia, and inflammatory processes that occur during reperfusion and contribute to continued tubular cell injury. Vascular endothelial cell injury and dysfunction play a vital part in this extension phase. With injury, the endothelial cell loses its ability to regulate vascular tone, perfusion, permeability and inflammation/adhesion. This loss of regulatory function has a detrimental impact upon renal function. Vascular congestion, edema formation, diminished blood flow, and infiltration of inflammatory cells have been documented in the corticomedullary junction of the kidney. However, linking their genesis to microvascular endothelial injury and dysfunction has been difficult. New diagnostic and therapeutic approaches to ischemic ARF must incorporate these finding to devise early recognition strategies and therapeutic approaches.

Acute Kidney Injury↗

PubMed2003

Injury of the renal microvascular endothelium alters barrier function after ischemia.

The role of renal microvascular endothelial cell injury in the pathophysiology of ischemic acute renal failure (ARF) remains largely unknown. No consistent morphological alterations have been ascribed to the endothelium of the renal microvasculature as a result of ischemia-reperfusion injury. Therefore, the purpose of this study was to examine biochemical markers of endothelial injury and morphological changes in the renal microvascular endothelium in a rodent model of ischemic ARF. Circulating von Willebrand factor (vWF) was measured as a marker of endothelial injury. Twenty-four hours after ischemia, circulating vWF peaked at 124% over baseline values (P = 0.001). The FVB-TIE2/GFP mouse was utilized to localize morphological changes in the renal microvascular endothelium. Immediately after ischemia, there was a marked increase in F-actin aggregates in the basal and basolateral aspect of renal microvascular endothelial cells in the corticomedullary junction. After 24 h of reperfusion, the pattern of F-actin staining was more similar to that observed under physiological conditions. In addition, alterations in the integrity of the adherens junctions of the renal microvasculature, as demonstrated by loss of localization in vascular endothelial cadherin immunostaining, were observed after 24 h of reperfusion. This observation temporally correlated with the greatest extent of permeability defect in the renal microvasculature as identified using fluorescent dextrans and two-photon intravital imaging. Taken together, these findings indicate that renal vascular endothelial injury occurs in ischemic ARF and may play an important role in the pathophysiology of ischemic ARF.

Actin Cytoskeleton↗

PubMed2002

Microvascular endothelial injury and dysfunction during ischemic acute renal failure.

The pathophysiology of ischemic acute renal failure (ARF) appears to involve a complex interplay between renal hemodynamics, tubular injury, and inflammatory processes. While the current paradigm of the pathophysiology of ischemic ARF invokes both sublethal and lethal tubular injury as being of paramount importance to diminished renal function, a growing body of evidence supports the contribution of altered renal vascular function in potentially initiating and subsequently extending the initial tubular injury. We propose that the "extension phase" of ischemic ARF involves alterations in renal perfusion, continued hypoxia, and inflammatory processes that all contribute to continued tubular cell injury. Vascular endothelial cell injury and dysfunction play a vital part in this extension phase. In the constitutive state the endothelium regulates migration of inflammatory cells into tissue, vascular tone and perfusion, vasopermeability, and prevents coagulation. Upon injury, the endothelial cell loses its ability to regulate these functions. This loss of regulatory function can have a subsequent detrimental impact upon renal function. Vascular congestion, edema formation, diminished blood flow, and infiltration of inflammatory cells have been documented in the corticomedullary junction of the kidney, but linking their genesis to vascular endothelial injury and dysfunction has been difficult. However, new investigative approaches, including multiphoton microscopy and the Tie2-GFP mouse, have been developed that will further our understanding of the roles endothelial injury and dysfunction play in the pathophysiology of ischemic ARF. This knowledge should provide new diagnostic and therapeutic approaches to ischemic ARF.

Acute Kidney Injury↗

PubMed2002

Endothelial injury and dysfunction in ischemic acute renal failure.

Ischemic acute renal failure is the most common cause of acute renal failure in hospitalized patients and has an average mortality rate of 50%. Although epithelial and vascular smooth muscle cell abnormalities have been clearly delineated in association with this condition, the extent of endothelial injury and dysfunction has been difficult to document, primarily for anatomic reasons. However, endothelial tight junction separation and endothelial cell detachment, blebbing, and necrosis have been observed after ischemia in other organs. In addition, adenosine triphosphate depletion studies in cultured endothelial cells have demonstrated that multiple actin-based alterations occur in a reversible and duration-dependent fashion. After an ischemic insult, total renal blood flow returns toward normal, but marked, regional alterations occur. Most affected is the outer medullary or corticomedullary junction region where blood flow remains approximately 10% of normal. In this area, the microvasculature becomes congested. Interstitial edema, red blood cell trapping, leukocyte adherence, and extravasation all contribute to this congestion. Increased expression of both P selectin and E selectin has been documented in renal endothelial cells after ischemic injury, and treatment with antibodies to either intercellular adhesion molecule-1, P selectins, or E selectins has been shown to minimize renal injury. During ischemia in vivo and adenosine triphosphate depletion in cell culture studies, F-actin destruction occurs, with polymerization leading to accumulation of intracellular actin aggregates. By using multiphoton microscopy, Voxx software, and the Tie-2 mouse with selective endothelial cell green fluorescent protein expression driven by the Tie-2 promoter, we have been able to identify macrovascular and microvascular endothelial cells in four dimensions (three dimensions plus time) intravitally. By using Texas red-labeled large molecular weight dextrans, we can document blood flow and vascular dysfunction. Intravital studies using multiphoton imaging techniques can now be conducted to identify and quantify endothelial cell injury and dysfunction in functioning organs.

Acute Kidney Injury↗