Antioxidant expression in experimental hydronephrosis: role of mechanical stretch and growth factors.

We assessed whether levels of renal reactive oxygen species (ROS) and antioxidant enzymes are perturbed in rats following unilateral ureteral obstruction (UUO). The mechanism of catalase perturbation was investigated using proximal tubule suspensions following stimulation with transforming growth factor (TGF)-beta and interleukin (IL)-1 and in a proximal tubular cell line (OKC) subjected to cyclic mechanical stretch, which mimics the early hydrodynamic derangement after UUO. Levels of catalase and copperzinc superoxide dismutase (Cu,Zn-SOD) mRNA from 96-h UUO rats showed a 5.5-fold (P < 0.001) and 5.0-fold (P < 0.001) decrease, respectively, compared with the contralateral unobstructed kidney (CUK). Levels of superoxide anion and hydrogen peroxide showed a significant 1.8-fold (P < 0.0001) and 14.0-fold (P < 0.0001) increase, respectively, in 96-h UUO kidney slice cultures. In situ hybridization and immunohistochemistry showed Cu,Zn-SOD and catalase mRNA and protein transcription expressed in proximal tubules of UUO and CUK specimens. Catalase mRNA levels were markedly downregulated following a 1-h exposure of isolated proximal tubules to TGF-beta (0.1-10 ng) and IL-1 (1-5 ng), in comparison to control proximal tubular suspensions. OKC subjected to cyclic mechanical stretch for 1-24 h had marked decrements in catalase mRNA levels, compared with unstretched cells at the same time point. These results indicate that a primary downregulation of proximal tubular Cu,Zn-SOD and catalase expression develops in the proximal tubules of UUO with consequent increments in cortical oxidant levels. These findings suggest that either an early mechanical disturbance produced by UUO or local tubular generation of cytokines can reduce tubular catalase expression. The downregulation of catalase mRNA expression, together with increased oxidant stress in the rat renal cortex post-UUO, may amplify the proinflammatory state of experimental hydronephrosis culminating in tubulointerstitial injury and fibrosis.

Early and persistent up-regulated expression of renal cortical osteopontin in experimental hydronephrosis.

The mechanical disturbance after unilateral ureteral obstruction (UUO) is a nonimmune stimulus that is capable of eliciting a florid macrophage infiltration of the kidney and subsequent post-inflammatory renal scarring. Osteopontin has potential chemoattractant activity and, for this reason, we delineated the kinetics of its expression in the renal cortex of rats with UUO. Whole body X-irradiation and reversal of UUO were utilized as interventional maneuvers to give additional pathobiological insight into this protein's role in the response of the kidneys to ureteral obstruction. Increased osteopontin mRNA levels in obstructed kidneys versus contralateral unobstructed specimens were evident as early as 4 hours after UUO and steadily increased at 12, 24, 48, and 96 hours after UUO. Both X-irradiation and reversal of UUO failed to significantly modulate renal cortical osteopontin mRNA expression at all of the above time points. Paralleling the increments in renal cortical osteopontin mRNA levels were significant elevations in the cortical renal interstitial macrophage number, which was significantly diminished by previous X-irradiation but not reversal of UUO. Focal labeling of osteopontin was noted in both tubular and Bowman's capsular epithelium in obstructed kidneys as early as 4 hours after UUO, whereas, in the contralateral unobstructed specimens, there was only faint staining in Bowman's capsule. By 96 hours after UUO, obstructed kidneys exhibited intense, diffuse staining for osteopontin in both tubules and Bowman's capsule. Osteopontin's immunolocalization was not modulated by X-irradiation or reversal of UUO. These data support the contention that osteopontin is involved in the accumulation of macrophages within the peritubular and periglomerular interstitium in the obstructed renal cortex.

Inhibition of myointimal proliferation of the rat carotid artery by the peptides, angiopeptin and BIM 23034.

Proliferation of vascular smooth muscle is an early and major event in the formation of an atherosclerotic lesion. Here we report for the first time the inhibitory effects on myointimal proliferation of the rat carotid artery by a synthetic peptide, angiopeptin, and its closely related congener, BIM 23034. Proliferation was initiated in the carotid artery of anesthetized rats by air-drying of the endothelium. After 15 days the rats were killed and the carotid artery was pressure-fixed and subjected to morphologic analysis for evaluation of the degree of myointimal thickening. Five synthetic somatostatin-like peptides were tested by pretreating rats (20 and 50 micrograms/kg/rat s.c. daily) for 2 days prior to and for 5 days after the endothelial injury. Angiopeptin and the closely related octapeptide (BIM 23034) significantly inhibited myointimal thickening. Angiopeptin was also effective when the pretreatment period was reduced from 2 days to 30 min. The inhibitory effect of angiopeptin was further confirmed in an additional experiment involving [3H]thymidine incorporation. In this experiment angiopeptin (100 micrograms/kg/day s.c.) was also administered for 2 days prior to and five days following the endothelial injury and it significantly inhibited thymidine uptake. All the peptides tested inhibit the release of growth hormone. However, only angiopeptin and BIM 23034 inhibited myointimal proliferation. Thus the effect of angiopeptin and its congener is unlikely to be mediated through growth hormone. Since angiopeptin inhibits myointimal proliferation it may have clinical utility in preventing restenosis following angioplasty and coronary artery by-pass procedures.

Occult mucous airway obstruction in diabetic ketoacidosis.

Four patients with diabetes mellitus and no underlying clinical pulmonary disease were found to have extensive unilateral mucous occlusion of a major central bronchus. None of the patients had significant auscultatory findings suggestive of pulmonary secretions, and chest roentgenographic films were normal. Arterial blood gas evaluation failed to reveal the usual hypocapnia during ketoacidosis, thus prompting bronchoscopic examination or deep airway suctioning. These interventions disclosed and resolved the mucous obstruction of the compromised bronchus. Antibiotic therapy, based upon bronchial secretion Gram stain and culture, was successfully instituted in all patients. Lethargy and autonomic neuropathy are proposed as contributing factors responsible for occult mucous plugging in diabetic patients in ketoacidosis. The absence of hypocapnia in this setting may be the only clue to silent mucous plugging of airways.