In vivo and in vitro models demonstrate a role for caveolin-1 in the pathogenesis of ischaemic acute renal failure

Caveolae and their proteins, the caveolins, transport macromolecules; compartmentalize signalling molecules; and are involved in various repair processes. There is little information regarding their role in the pathogenesis of significant renal syndromes such as acute renal failure (ARF). In this study, an in vivo rat model of 30 min bilateral renal ischaemia followed by reperfusion times from 4 h to 1 week was used to map the temporal and spatial association between caveolin-1 and tubular epithelial damage (desquamation, apoptosis, necrosis). An in vitro model of ischaemic ARF was also studied, where cultured renal tubular epithelial cells or arterial endothelial cells were subjected to injury initiators modelled on ischaemia-reperfusion (hypoxia, serum deprivation, free radical damage or hypoxia-hyperoxia). Expression of caveolin proteins was investigated using immunohistochemistry, immunoelectron microscopy, and immunoblots of whole cell, membrane or cytosol protein extracts. In vivo, healthy kidney had abundant caveolin-1 in vascular endothelial cells and also some expression in membrane surfaces of distal tubular epithelium. In the kidneys of ARF animals, punctate cytoplasmic localization of caveolin-1 was identified, with high intensity expression in injured proximal tubules that were losing basement membrane adhesion or were apoptotic, 24 h to 4 days after ischaemia-reperfusion. Western immunoblots indicated a marked increase in caveolin-1 expression in the cortex where some proximal tubular injury was located. In vitro, the main treatment-induced change in both cell types was translocation of caveolin-1 from the original plasma membrane site into membrane-associated sites in the cytoplasm. Overall, expression levels did not alter for whole cell extracts and the protein remained membrane-bound, as indicated by cell fractionation analyses. Caveolin-1 was also found to localize intensely within apoptotic cells. The results are indicative of a role for caveolin-1 in ARF-induced renal injury. Whether it functions for cell repair or death remains to be elucidated.     

Cell death and cell proliferation during atrophy of the rat parotid gland induced by duct obstruction

Rat parotid gland atrophy after unilateral duct ligation was studied by light and electron microscopy. Death of secretory acinar cells, which took the form of apoptosis, resulted in their complete disappearance within 5 days. The remnants of the dying cells were mostly phagocytosed and degraded by macrophages within the glandular epithelium; a few were taken up by adjoining epithelial cells. The acinar cell deletion was accompanied by increased mitosis of striated and intercalated duct epithelial cells. However, over many weeks, there was enhanced apoptosis of duct cells, which eventually led to marked shortening of intercalated ducts. Apoptosis of capillary endothelial cells was observed and may account for the reduction in the capillary bed known to accompany gland atrophy. The end-stage lesion comprised small numbers of ducts in a condensed stroma. Compensatory hyperplasia, involving proliferation of duct and acinar cells, was demonstrated in the contralateral glands.     

Cell death by apoptosis following X-irradiation of the foetal and neonatal rat kidney

A light and electron microscopic study was undertaken to determine the type of cell death induced by X-irradiation in the developing kidney. Five-day-old Sprague-Dawley rats were exposed to a whole-body dose of either 2 or 5 Gy, and foetuses in the eighteenth day of development were exposed to a dose of 4 Gy. The kidneys were examined at 4, 8 and 24 h, and at 1 and 2 weeks post-irradiation. The dying cells from both control and treated kidneys showed the morphological features of apoptosis, a distinct form of cell death that has been identified in mammalian tissues under physiological as well as pathological conditions. Necrosis was not detected. Apoptosis was infrequent in control kidneys and insignificant in extent when compared with the proliferative activity of the cells of the superficial nephrons. There was a pronounced increase in apoptosis during the first day after irradiation. The findings are in agreement with recent ultrastructural studies which report the presence of apoptosis following irradiation of rapidly proliferating adult cell populations, and irradiation of other immature mammalian tissues. There is evidence that apoptosis involves active cellular self-destruction, and it has been suggested that activation of apoptosis might bring about selective elimination of cells with critical DNA damage in irradiated tissues, thus minimizing propagation of genetic abnormalities.     

An experimental study evaluating the effect of minoxidil on the growth cycle of hair follicles

The possibility that topically-applied minoxidil might affect the growth cycle of hair follicles was studied in inbred Herston white mice and HRA/Skh1 hairless mice. In the normal follicular cycle, the anagen or growth phase can be followed by autoradiographic demonstration of [3H]thymidine uptake in proliferating matrical cells, and the catagen or regression phase can be recognised, using light microscopy, by the presence of greatly increased death of matrical cells by apoptosis. Using these two markers, the effects of topically-applied minoxidil on follicular kinetics were studied, during neonatal hair growth and the spontaneous wave of hair loss that occurs 16 to 17 days after birth. Minoxidil at strengths of either 1% or 3%, applied daily to the dorsal skin of newborn mice from birth until 25 days of age, was found to have no recognisable effect. Despite this negative result, however, the study does show the potential for the use of apoptosis as a marker for catagen in research in dermatopathology.     

Cell survival or death in renal tubular epithelium after ischemia-reperfusion injury.

A major contributor to the development and progression of ischemia-reperfusion (IR)-induced acute renal failure (ARF) is the loss of functioning tubular epithelial cells by means of various cell deletion or death processes. Although the term "acute tubular necrosis" is still used to describe the pathology of ARF, this is a misnomer because apoptotic cell death, as well as necrosis, occurs [1, 2] along with desquamation and loss of viable epithelial cells [3]. Apoptosis was first described in renal disease in 1987 in an animal model of hydronephrosis [4]. In ARF, with reference to only the death processes, the relative contribution of necrosis or apoptosis possibly depends on the extent of the initiating events. For example, after prolonged total renal ischemia, necrosis or "accidental cell death" occurs from the resultant negation of the cell's energy and protein levels. In apoptosis, the cells use their own energy processes and proteins to die, and often the initiating ischemia is more mild [5]. Finally, despite prolonged ischemia, within the heterogeneous renal cell populations there are those that are more sensitive to ischemia, such as the proximal straight tubule and to some extent the thick ascending limb (TAL) of the loop of Henle. It may be hypothesized that these cells tend to undergo necrosis in comparison with the less sensitive segments that undergo apoptosis. Because apoptosis is gene driven, its identification is important because of the possibility of its modulation via molecular controls. However, despite these new concepts of ARF, patient death remains high, at approximately 30 to 50% of ARF cases. Recovery from ARF depends not only on the replacement or regeneration of cells deleted by death, the theme of many recent studies, but also on protection of cells from death. Both processes are dependent on many of the cellular and molecular controls that have evolved in multicellular organisms to manage normal development, differentiation and growth processes, but that then become involved in the pathogenesis and progression of many renal diseases, including ARF.     

Angiotensin II facilitates autoregulation in the perfused mouse kidney: An optimized in vitro model for assessment of renal vascular and tubular function

BACKGROUND AND AIMS: We have optimized the isolated perfused mouse kidney (IPMK) model for studying renal vascular and tubular function in vitro using 24-28 g C57BL6J mice; the wild type controls for many transgenic mice. METHODS AND RESULTS: Buffer composition was optimized for bovine serum albumin concentration (BSA). The effect of adding erythrocytes on renal function and morphology was assessed. Autoregulation was investigated during stepped increases in perfusion pressure. Perfusion for 60 min at 90-110 mmHg with Krebs bicarbonate buffer containing 5.5% BSA, and amino acids produced functional parameters within the in vivo range. Erythrocytes increased renal vascular resistance (3.8 +/- 0.2 vs 2.4 +/- 0.1 mL/min.mmHg, P < 0.05), enhanced sodium reabsorption (FE(Na) = 0.3 +/- 0.08 vs 1.5 +/- 0.7%, P < 0.05), produced equivalent glomerular filtration rates (GFR; 364 +/- 38 vs 400 +/- 9 microL/min per gkw) and reduced distal tubular cell injury in the inner stripe (5.8 +/- 1.7 vs 23.7 +/- 3.1%, P < 0.001) compared to cell free perfusion. The IPMK was responsive to vasoconstrictor (angiotensin II, EC50 100 pM) and vasodilator (methacholine, EC50 75 nM) mediators and showed partial autoregulation of perfusate flow under control conditions over 65-85 mmHg; autoregulatory index (ARI) of 0.66 +/- 0.11. Angiotensin II (100 pM) extended this range (to 65-120 mmHg) and enhanced efficiency (ARI 0.21 +/- 0.02, P < 0.05). Angiotensin II facilitation was antagonized by methacholine (ARI 0.76 +/- 0.08) and papaverine (ARI 0.91 +/- 0.13). CONCLUSION: The IPMK model is useful for studying renal physiology and pathophysiology without systemic neurohormonal influences.     

Follow-up of prostate cancer patients by on-demand contacts with a specialist nurse: a randomized study

OBJECTIVE: The effectiveness of traditional follow-up programs and the intensive search for disease progression in men with prostate cancer have been questioned. The aims of this randomized multi-centre study were to evaluate medical safety, patient satisfaction and resource utilization in an on-demand follow-up by a specialist nurse compared with traditional follow-up by a urologist. MATERIAL AND METHODS: Four hundred consecutively approached men with newly diagnosed or previously known prostate cancer in any stage at three hospitals in Sweden were randomized to follow-up in the nurse group (NG, 200 patients) or the urologist group (UG, 200 patients). In the NG, the nurse contacted the patient by phone every 6 months unless the patient himself initiated the contact. Patient satisfaction was evaluated twice a year via questionnaire. The questionnaire included the validated Hospital Anxiety and Depression Scale (HADS). The costs of all medical interventions and adverse events related to prostate cancer were calculated for all patients. RESULTS: Medical safety, measured as complication frequency and lag time from symptoms to intervention, during the first 3 years of the observation period, was similar in the NG and the UG. The total number of interventions due to symptoms from prostate cancer was also similar in both groups. The analysis of accessibility and the HAD scale showed no significant differences between the groups. The mean outpatient cost (excluding pharmaceutical costs) per patient was lower in the NG compared to the UG, especially among patients without metastases at inclusion (37% lower cost). CONCLUSIONS: Our study indicates that men with prostate cancer can be safely followed up by a specialist nurse. The study results show that this alternative follow-up is cost-effective, especially in men without metastases.