For the past decade, an attempt has been made by many research groups to define the roles of the growing number of Bcl‐2 gene family proteins in the apoptotic process. The Bcl‐2 family consists of pro‐apoptotic (or cell death) and anti‐apoptotic (or cell survival) genes and it is the balance in expression between these gene lineages that may determine the death or survival of a cell. The majority of studies have analysed the role/s of the Bcl‐2 genes in cancer development. Equally important is their role in normal tissue development, homeostasis and non‐cancer disease states. Bcl‐2 is crucial for normal development in the kidney, with a deficiency in Bcl‐2 producing such malformation that renal failure and death result. As a corollary, its role in renal disease states in the adult has been sought. Ischaemia is one of the most common causes of both acute and chronic renal failure. The section of the kidney that is most susceptible to ischaemic damage is the outer zone of the outer medulla. Within this zone the proximal tubules are most sensitive and often die by necrosis or desquamate. In the distal nephron, apoptosis is the more common form of cell death. Recent results from our laboratory have indicated that ischaemia‐induced acute renal failure is associated with up‐regulation of two anti‐apoptotic Bcl‐2 proteins (Bcl‐2 and Bcl‐X L ) in the damaged distal tubule and occasional up‐regulation of Bax in the proximal tubule. The distal tubule is a known reservoir for several growth factors important to renal growth and repair, such as insulin‐like growth factor‐1 (IGF‐1) and epidermal growth factor (EGF). One of the likely possibilities for the anti‐cell death action of the Bcl‐2 genes is that the protected distal cells may be able to produce growth factors that have a further reparative or protective role via an autocrine mechanism in the distal segment and a paracrine mechanism in the proximal cells. Both EGF and IGF‐1 are also up‐regulated in the surviving distal tubules and are detected in the surviving proximal tubules, where these growth factors are not usually synthesized. As a result, we have been using in vitro methods to test: (i) the relative sensitivities of renal distal and proximal epithelial cell populations to injury caused by mechanisms known to act in ischaemia–reperfusion; (ii) whether a Bcl‐2 anti‐apoptotic mechanism acts in these cells; and (iii) whether an autocrine and/or paracrine growth factor mechanism is initiated. The following review discusses the background to these studies as well as some of our preliminary results.
Background: Silver dressings have been widely and successfully used to prevent cutaneous wounds, including burns, chronic ulcers, dermatitis and other cutaneous conditions, from infection. However, in a few cases, skin discolouration or argyria‐like appearances have been reported. This study investigated the level of silver in scar tissue post‐burn injury following application of Acticoat™, a silver dressing. Methods: A porcine deep dermal partial thickness burn model was used. Burn wounds were treated with this silver dressing until completion of re‐epithelialization, and silver levels were measured in a total of 160 scars and normal tissues. Results: The mean level of silver in scar tissue covered with silver dressings was 136 μg/g, while the silver level in normal skin was less than 0.747 μg/g. A number of wounds had a slate‐grey appearance, and dissection of the scars revealed brown‐black pigment mostly in the middle and deep dermis within the scar. The level of silver and the severity of the slate‐grey discolouration were correlated with the length of time of the silver dressing application. Conclusions: These results show that silver deposition in cutaneous scar tissue is a common phenomenon, and higher levels of silver deposits and severe skin discolouration are correlated with an increase in the duration of this silver dressing application.
The anticonvulsant phenytoin (5,5-diphenylhydantoin) provokes a skin rash in 5 to 10% of patients, which heralds the start of an idiosyncratic reaction that may result from covalent modification of normal self proteins by reactive drug metabolites. Phenytoin is metabolized by cytochrome P450 (P450) enzymes primarily to 5-(p-hydroxyphenyl-),5-phenylhydantoin (HPPH), which may be further metabolized to a catechol that spontaneously oxidizes to semiquinone and quinone species that covalently modify proteins. The aim of this study was to determine which P450s catalyze HPPH metabolism to the catechol, proposed to be the final enzymatic step in phenytoin bioactivation. Recombinant human P450s were coexpressed with NADPH-cytochrome P450 reductase in Escherichia coli. Novel bicistronic expression vectors were constructed for P450 2C19 and the three major variants of P450 2C9, i.e., 2C9*1, 2C9*2, and 2C9*3. HPPH metabolism and covalent adduct formation were assessed in parallel. P450 2C19 was the most effective catalyst of HPPH oxidation to the catechol metabolite and was also associated with the highest levels of covalent adduct formation. P450 3A4, 3A5, 3A7, 2C9*1, and 2C9*2 also catalyzed bioactivation of HPPH, but to a lesser extent. Fluorographic analysis showed that the major targets of adduct formation in bacterial membranes were the catalytic P450 forms, as suggested from experiments with human liver microsomes. These results suggest that P450 2C19 and other forms from the 2C and 3A subfamilies may be targets as well as catalysts of drug-protein adduct formation from phenytoin.
Fibrogenic stresses promote progression of renal tubulointerstitial fibrosis, disparately affecting survival, proliferation and trans-differentiation of intrinsic renal cell populations through ill-defined biomolecular pathways. We investigated the effect of fibrogenic stresses on the activation of cell-specific mitogen-activated protein kinase (MAPK) in renal fibroblast, epithelial and endothelial cell populations. The relative outcomes (cell death, proliferation, trans-differentiation) associated with activation or inhibition of extracellular-regulated protein kinase (ERK) or stress activated/c-Jun N terminal kinase (JNK) were analysed in each renal cell population after challenge with oxidative stress (1 mmol/L H2O2), transforming growth factor-beta1 (TGF-beta1, 10 ng/mL) or tumour necrosis factor-alpha (TNF-alpha, 50 ng/mL) over 0-20 h. Apoptosis increased significantly in all cell types after oxidative stress (P < 0.05). In fibroblasts, oxidative stress caused the activation of ERK (pERK) but not JNK (pJNK). Inhibition of ERK by PD98059 supported its role in a fibroblast death pathway. In epithelial and endothelial cells, oxidative stress-induced apoptosis was preceded by early induction of pERK, but its inhibition did not support a pro-apoptotic role. Early ERK activity may be conducive to their survival or promote the trans-differentiation of epithelial cells. In epithelial and endothelial cells, oxidative stress induced pJNK acutely. Pretreatment with SP600125 (JNK inhibitor) verified its pro-apoptotic activity only in epithelial cells. Transforming growth factor-beta1 did not significantly alter mitosis or apoptosis in any of the cell types, nor did it alter MAPK activity. Tumor necrosis factor-alpha caused increased apoptosis with no associated change in MAPK activity. Our results demonstrate renal cell-specific differences in the activation of ERK and JNK following fibrotic insult, which may be useful for targeting excessive fibroblast proliferation in chronic fibrosis.
Acute application of adjunctive negative pressure wound therapy (NPWT) significantly improves time to re-epithelialization in pediatric burn patients. This adjunctive treatment has not yet been broadly or routinely adopted as a standard primary burns dressing strategy. The Implementation of Negative PRessurE for acute Pediatric burns (INPREP) trial will implement and evaluate the impact of adjunctive NPWT in parallel with co-designed implementation strategies and resources across four major pediatric hospitals.
Abstract First aid treatment of burn injuries reduces scarring and improves healing. Here, we quantify the efficacy of various first aid treatments by using a mathematical model to describe a suite of experimental data from a series of in vivo porcine experiments. We study a series of consistent burn injuries that are subject to first aid treatments that vary in both the temperature and duration of the first aid treatment. Calibrating the mathematical model to the experimental data provides estimates of the in vivo thermal diffusivity, the rate at which thermal energy is lost to the blood (perfusion), and the heat transfer coefficient controlling the loss of thermal energy at the interface of the fat and muscle layers. A limitation of working with in vivo animal experiments is the difficulty of resolving spatial variations in temperature across the tissues. Here, we use the solution of the calibrated mathematical model to predict and visualise the temperature distribution across the thickness of the tissue during the creation of the burn injury and the application of various first aid treatments. Using this information we propose, and report values for, a novel measure of the potential for tissue damage. This measure quantifies two important aspects that are thought to be related to thermal injury: (i) the volume of tissue that rises above the threshold temperature associated with the accumulation of tissue damage; and, (ii) the duration of time that the tissue remains above this threshold temperature. We conclude by discussing the clinical relevance of our findings.
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)