Faculty development to improve teaching at a health sciences center: a needs assessment.

There has been increasing interest at health science centers in improving the education of health professionals by offering faculty development activities. In 2007-08, as part of an effort to expand education-related faculty development offerings on campus, the University of Tennessee Health Science Center surveyed faculty members in an effort to identify faculty development activities that would be of interest. Factor analysis of survey data indicated that faculty interests in the areas of teaching and learning can be grouped into six dimensions: development of educational goals and objectives, the use of innovative teaching techniques, clinical teaching, improving traditional teaching skills, addressing teaching challenges, and facilitating participation. There were significant differences in the level of interest in education-related faculty development activities by academic rank and by the college of appointment. Full professors expressed somewhat less interest in faculty development activities than faculty members of lower ranks. Faculty members in the Colleges of Medicine and Dentistry expressed somewhat greater interest in faculty development to improve traditional teaching skills. The policy implications of the survey results are discussed, including the need for faculty development activities that target the needs of specific faculty groups.

Oxalate toxicity in renal cells.

Exposure to oxalate, a constituent of the most common form of kidney stones, generates toxic responses in renal epithelial cells, including altered membrane surface properties and cellular lipids, changes in gene expression, disruption of mitochondrial function, formation of reactive oxygen species and decreased cell viability. Oxalate exposure activates phospholipase A2 (PLA2), which increases two lipid signaling molecules, arachidonic acid and lysophosphatidylcholine (Lyso-PC). PLA2 inhibition blocks, whereas exogenous Lyso-PC or arachidonic acid reproduce many of the effects of oxalate on mitochondrial function, gene expression and cell viability, suggesting that PLA2 activation plays a role in mediating oxalate toxicity. Oxalate exposure also elicits potentially adaptive or protective changes that increase expression of proteins that may prevent crystal formation or attachment. Additional adaptive responses may facilitate removal and replacement of dead or damaged cells. The presence of different inflammatory cells and molecules in the kidneys of rats with hyperoxaluria and in stone patients suggests that inflammatory responses play roles in stone disease. Renal epithelial cells can synthesize a variety of cytokines, chemoattractants and other molecules with the potential to interface with inflammatory cells; moreover, oxalate exposure increases the synthesis of these molecules. The present studies demonstrate that oxalate exposure upregulates cyclooxygenase-2, which catalyzes the rate-limiting step in the synthesis of prostanoids, compounds derived from arachidonic acid that can modify crystal binding and may also influence inflammation. In addition, renal cell oxalate exposure promotes rapid degradation of IkappaBalpha, an endogenous inhibitor of the NF-kappaB transcription factor. A similar response is observed following renal cell exposure to lipopolysaccharide (LPS), a bacterial cell wall component that activates toll-like receptor 4 (TLR4). While TLRs are primarily associated with immune cells, they are also found on many other cell types, including renal epithelial cells, suggesting that TLR signaling could directly impact renal function. Prior exposure of renal epithelial cells to oxalate in vitro produces endotoxin tolerance, i.e. a loss of responsiveness to LPS and conversely, prior exposure to LPS elicits a similar heterologous desensitization to oxalate. Renal cell desensitization to oxalate stimulation may have profound effects on the outcome of renal stone disease by impairing protective responses.

Mitochondrial dysfunction is a primary event in renal cell oxalate toxicity.

BACKGROUND: In cultured renal epithelial cells, exposure to oxalate, a constituent of many kidney stones, elicits a cascade of responses that often leads to cell death. Oxalate toxicity is mediated via generation of reactive oxygen species (ROS) in a process that depends at least in part upon lipid signaling molecules that are generated through membrane events that culminate in phospholipase A2 (PLA2) activation. The present studies asked whether mitochondria, a major site of ROS production, were targets of oxalate toxicity, and if so, whether mitochondrial responses to oxalate were mediated by PLA2 activation. METHODS: Effects of oxalate and various lipids on mitochondrial membrane potential (DeltaPsim) were measured in Madin-Darby canine kidney (MDCK) cell monolayers using 5,5',6,6'-tetrachloro 1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide (JC-1), a DeltaPsim-sensitive dye. Other studies assayed caspases, serine proteases activated during apoptosis, in response to oxalate or lipid signaling molecules. Additional studies asked whether oxalate or lipids produced by PLA2 activation promoted ROS formation in isolated renal mitochondria. RESULTS: Oxalate exposure decreased MDCK cell DeltaPsim within 30 minutes, a response attenuated by arachidonyl trifluoromethyl ketone (AACOCF3), an inhibitor of cytosolic PLA2 (cPLA2). Exposure to arachidonic acid or to lysophosphatidylcholine (lyso-PC), lipid products of PLA2 activation, or to ceramide, another lipid signal generated in MDCK cells following oxalate exposure, also depolarized MDCK cell DeltaPsim and increased the number of caspase-positive cells. Isolated renal mitochondria responded to oxalate, arachidonic acid, lyso-PC, and ceramide by increasing their accumulation of ROS, lipid peroxides, and oxidized thiol proteins. CONCLUSION: These studies suggest that lipid signaling molecules released after oxalate-induced PLA2 activation trigger marked, rapid changes in mitochondrial function that may mediate toxicity in renal epithelial cells.

Intracellular events in the initiation of calcium oxalate stones.

This review summarizes our current understanding of intracellular events in the initiation of kidney stone formation, focusing on results from studies using renal epithelial cells in vitro. Such studies have shown that oxalate - either in crystalline or in soluble form - triggers a spectrum of responses in renal cells that favor stone formation, including alterations in membrane surface properties that promote crystal attachment and alterations in cell viability that provide debris for crystal nucleation. Activation of cytosolic PLA2 appears to play an important role in oxalate actions, triggering a signaling cascade that generates several lipid mediators (arachidonic acid, AA; lysophosphatidylcholine, Lyso-PC; ceramide) that act on key intracellular targets (mitochondria, nucleus). The net effect is increased production of reactive oxygen molecules (that in turn affect other cellular processes), an increase in cell death and an induction of a number of genes in surviving cells, some of which may promote proliferation for replacement of damaged cells, or may promote secretion of urinary macromolecules that serve to modulate crystal formation. A scheme is provided that explains how such oxalate-induced alterations could initiate stone formation in vivo.

How elevated oxalate can promote kidney stone disease: changes at the surface and in the cytosol of renal cells that promote crystal adherence and growth.

The present review assesses the mechanisms by which oxalate-induced alterations in renal cell function may promote stone disease focusing on 1) changes in membrane surface properties that promote the attachment of nascent crystals and 2) changes in the expression/secretion of urinary macromolecules that alter the kinetics of crystal nucleation, agglomeration and growth. The general role of renal cellular injury in promoting these responses and the specific role of urinary oxalate in producing injury is emphasized, and the signaling pathways that lead to the observed changes in cell surface properties and in the viability and growth of renal cells are discussed. Particular attention is paid to evidence linking oxalate-induced activation of cytosolic phospholipase A2 to changes in gene expression and to the activation of a second signaling pathway involving ceramide. The effects of the lipid signals, arachidonic acid, lysophosphatidylcholine and ceramide, on mitochondrial function are considered in some detail since many of the actions of oxalate appear to be secondary to increased production of reactive oxygen molecules within these organelles. Data from these studies and from a variety of other studies in vitro and in vivo were used to construct a model that illustrates possible mechanisms by which an increase in urinary oxalate levels leads to an increase in kidney stone formation. Further studies will be required to assess the validity of various aspects of this proposed model and to determine effective strategies for countering these responses in stone-forming individuals.

Mechanisms mediating oxalate-induced alterations in renal cell functions.

Oxalate is a major component of the most common form of kidney stones--calcium oxalate stones. High concentrations of oxalate promote stone formation in two ways: (1) by providing urinary conditions favorable to the formation of calcium oxalate crystals, and (2) by inducing renal injury that generates cellular debris and promotes crystal nucleation and attachment. Oxalate toxicity is mediated in part by activation of lipid signaling pathways that produce arachidonic acid, lysophospholipids, and ceramide. These lipids disrupt mitochondrial function by increasing reactive oxygen species (ROS), decreasing mitochondrial membrane potential, and increasing mitochondrial permeability. The net response is cytochrome C release, activation of caspases, and apoptosis or necrosis. Not all cells succumb to oxalate toxicity, however, in those cells that don't, ROS and lipid-signaling molecules induce changes in gene expression that allow them to survive and adapt to the toxic insult. The increased expression of immediate early genes (IEGs), osteopontin, extracellular matrix (ECM) proteins, crystallization inhibitors, and chemokines orchestrates a group of cellular responses--including cell proliferation, secretion of kidney stone inhibitory proteins, recruitment of immune cells, and tissue remodeling--that limit accumulation of cell debris or increase the production of inhibitors of calcium oxalate crystallization, thereby limiting stone formation.