Dissociation of systemic and renal effects in endotoxemia. Prostaglandin inhibition uncovers an important role of renal nerves

The effects of acute renal denervation on kidney perfusion and metabolism in experimental septic shock

BACKGROUND

Perfusion deficits likely play an important role in the development of renal dysfunction in sepsis. Renal denervation may improve kidney perfusion and metabolism.

METHODS

We randomized 14 female sheep to undergo bilateral surgical renal denervation (n = 7) or sham procedure (n = 7) prior to induction of sepsis. Renal blood flow (RBF) was measured with a pre-calibrated flowprobe. Laser Doppler probes were implanted to measure cortical and medullary perfusion. Cortical glucose, lactate and pyruvate levels were measured using the microdialysis technique. Creatinine clearance was determined. Sepsis was induced by peritonitis and fluid resuscitation was provided to avoid hypovolemia.

RESULTS

RBF and cortical perfusion were higher in the denervated group during the first 6 h after induction of sepsis (P < 0.001 and P < 0.05, respectively), while medullary perfusion decreased similarly in both groups. After hypotension developed, RBF decreased to similar levels in both groups. Cortical pyruvate and lactate levels were lower in the denervated animals (P < 0.001 and P < 0.001, respectively). There were no differences between groups in creatinine clearance, urine output or time to oliguria.

CONCLUSION

Denervation thus caused an early increase in RBF that was distributed towards the kidney cortex. Although associated with an attenuation of early cortical metabolic alterations, denervation failed to prevent the deterioration in renal function.

Chymase activities and survival in endotoxin-induced human chymase transgenic mice

We examined the effects of overexpressed human chymase on survival and activity in lipopolysaccharide (LPS)-treated mice. Human chymase transgenic (Tg) and wild-type C57BL/6 (WT) mice were treated with LPS (0.03, 0.1 and 0.3 mg/day; intraperitoneal) for 2 weeks. Treatment with 0.03 mg LPS did not affect survival in either WT or Tg mice. WT mice were not affected by 0.1 mg/day of LPS, whereas 25% of Tg mice died. Survival of mice treated with 0.3 mg/day of LPS was 87.5% and 0% in WT and Tg, respectively. LPS-induced increases in chymase activity in the heart and skin were significantly greater in Tg than WT mice. These data suggest a possible contribution of human chymase activation to LPS-induced mortality.

Renal Vascular Resistance in Sepsis

AIMS

To assess changes in renal vascular resistance (RVR) in human and experimental sepsis and to identify determinants of RVR.

METHODS

We performed a systematic interrogation of two electronic reference libraries using specific search terms. Subjects were animals and patients involved in experimental and human studies of sepsis and septic acute renal failure, in which the RVR was assessed. We obtained all human and experimental articles reporting RVR during sepsis. We assessed the role of various factors that might influence the RVR during sepsis using statistical methods.

RESULTS

We found no human studies, in which the renal blood flow (and, therefore, the RVR) was measured with suitably accurate direct methods. Of the 137 animal studies identified, 52 reported a decreased RVR, 16 studies reported no change in RVR, and 69 studies reported an increased RVR. Consciousness of animals, duration of measurement, method of induction of sepsis, and fluid administration had no effect on the RVR. On the other hand, on univariate analysis, size of the animals (p < 0.001), technique of measurement (p = 0.017), recovery after surgery (p = 0.004), and cardiac output (p < 0.001) influenced the RVR. Multivariate analysis, however, showed that only cardiac output (p = 0.028) and size of the animals (p = 0.031) remained independent determinants of the RVR.

CONCLUSIONS

Changes in RVR during sepsis in humans are unknown. In experimental sepsis, several factors not directly related to sepsis per se appear to influence the RVR. A high cardiac output and the use of large animals predict a decreased RVR, while a decreased cardiac output and the use of small animals predict an increased RVR.

Renal blood flow in sepsis

Introduction

To assess changes in renal blood flow (RBF) in human and experimental sepsis, and to identify determinants of RBF.

Method

Using specific search terms we systematically interrogated two electronic reference libraries to identify experimental and human studies of sepsis and septic acute renal failure in which RBF was measured. In the retrieved studies, we assessed the influence of various factors on RBF during sepsis using statistical methods.

Results

We found no human studies in which RBF was measured with suitably accurate direct methods. Where it was measured in humans with sepsis, however, RBF was increased compared with normal. Of the 159 animal studies identified, 99 reported decreased RBF and 60 reported unchanged or increased RBF. The size of animal, technique of measurement, duration of measurement, method of induction of sepsis, and fluid administration had no effect on RBF. In contrast, on univariate analysis, state of consciousness of animals (P = 0.005), recovery after surgery (P < 0.001), haemodynamic pattern (hypodynamic or hyperdynamic state; P < 0.001) and cardiac output (P < 0.001) influenced RBF. However, multivariate analysis showed that only cardiac output remained an independent determinant of RBF (P < 0.001).

Conclusion

The impact of sepsis on RBF in humans is unknown. In experimental sepsis, RBF was reported to be decreased in two-thirds of studies (62 %) and unchanged or increased in one-third (38%). On univariate analysis, several factors not directly related to sepsis appear to influence RBF. However, multivariate analysis suggests that cardiac output has a dominant effect on RBF during sepsis, such that, in the presence of a decreased cardiac output, RBF is typically decreased, whereas in the presence of a preserved or increased cardiac output RBF is typically maintained or increased.

Protective effect of renal denervation on normotensive endotoxemia-induced acute renal failure in mice

Acute renal failure (ARF) contributes substantially to the high morbidity and mortality observed during endotoxemia. We hypothesized that selective blockade of the renal nerves would be protective against ARF during the early (16 h) stage of endotoxemia [5 mg lipopolysaccharide (LPS)/kg ip in mice]. At 16 h after LPS, there was no change in mean arterial pressure, but plasma epinephrine (4,604 +/- 719 vs. 490 +/- 152 pg/ml, P < 0.001), norepinephrine (2,176 +/- 306 vs. 1,224 +/- 218 pg/ml, P < 0.05), and plasma renin activity (40 +/- 5 vs. 27 +/- 2 ng x ml(-1) x h(-1), P < 0.05) were higher in the LPS-treated vs. control mice. The high plasma renin activity level decreased to the control level with renal denervation in endotoxemic mice. After intravenous injection of phentolamine (200 microg/kg), the decrement in mean arterial pressure was significantly greater in LPS-treated vs. control mice (19.4 +/- 3.5 vs. 8.1 +/- 1.5 mmHg, P < 0.01). Sixteen hours after LPS administration, there were significant decreases in glomerular filtration rate (52 +/- 18 vs. 212 +/- 23 microl/min, P < 0.01) and renal blood flow (0.58 +/- 0.08 vs. 0.85 +/- 0.06 ml/min, P < 0.01) in sham-operated mice. The decrement in glomerular filtration rate during endotoxemia was significantly attenuated in mice with denervated kidneys (32 vs. 79%). Moreover, there was no change in renal blood flow during endotoxemia in mice with renal denervation. The present results therefore demonstrate a protective role of renal denervation during normotensive endotoxemia-related ARF in mice, an effect that may be, at least in part, due to a diminished activation of the renin-angiotensin system.

Suppression of endotoxin-induced renal tumor necrosis factor-alpha and interleukin-6 mRNA by renin-angiotensin system inhibitors

The present study was designed to clarify the role of angiotensin II (Ang II) in modulating renal tumor necrosis factor (TNF)-alpha and interleukin-6 (IL-6) production and to investigate the effect of one dose of Ang II inhibitor on cytokines production following lipopolysaccharide (LPS) to cause endotoxemia. Two studies were performed: 1) Ang II was infused intravenously at a rate of 0.2 microg/kg per minute for 4 h in rats and then kidneys were collected to assay TNF-alpha and IL-6 mRNA levels; 2) Four-week-old Wistar rats pre-treated with angiotensin-converting enzyme inhibitor, enalapril, or type I Ang II-receptor antagonist, TCV-116, were injected with LPS (0.1, 0.5, 1.0 mg, i.p.), and then 2 or 4 h later, kidneys were collected to assay TNF-alpha, IL-6, renin and angiotensinogen mRNA levels. After a 4-h intravenous infusion of Ang II, renal TNF-alpha or IL-6 mRNA level significantly increased 1.9-fold or 2.1-fold (each P<0.05) to the control level, respectively. LPS stimulated TNF-alpha, IL-6 and angiotensinogen mRNA levels in the kidney but in rats given enalapril or TCV-116, LPS-induced IL-6 and TNF-alpha mRNA levels were completely suppressed (each P<0.05). This suggests that a single dose of renin-angiotensin system inhibitor suppressed renal IL-6 and TNF-alpha production and may prevent cytokine-induced renal damage during endotoxemia.

Inducible nitric oxide synthase attenuates endothelium-dependent renal microvascular vasodilation

Previous studies have demonstrated that inducible nitric oxide synthase (iNOS) plays a key pathophysiologic role during sepsis. The present study was designed to delineate the consequences of iNOS activation on renal microvascular function. Male Sprague-Dawley rats were given intraperitoneal injections of lipopolysaccharide (LPS; 4 mg/kg) at 16 h and 4 h before experimentation. Afferent and efferent arteriolar diameters from LPS-treated and control rats were assessed in vitro with the use of the blood perfused juxtamedullary nephron technique. Basal afferent and efferent arteriolar diameters of LPS-treated rats averaged 19.7 +/- 0.9 (n = 7) and 18.3 +/- 1.0 microm (n = 5), respectively, and were similar to those of control rats (20.8 +/- 0.3 [n = 6] and 18.4 +/- 0.6 microm [n = 6], respectively). Superfusion with the selective iNOS inhibitor S,S'-(1,3-phenylenebis[1,2-ethanediyl]) bisisothiourea (PBIT), at the doses of 0.01, 0.1, and 1 microM, significantly decreased afferent and efferent arteriolar diameters in a dose-dependent manner, whereas afferent or efferent arteriolar diameters of control rats were not altered in response to the same doses of PBIT. In the second series of experiments, superfusion with 10 microM acetylcholine (ACh) significantly increased afferent and efferent arteriolar diameters of LPS-treated rats by 14.9 +/- 1.6% (n = 9) and 6.6 +/- 1.1% (n = 6), respectively. The ACh-induced afferent and efferent arteriolar dilator responses were inhibited by superfusion with the nonselective NOS inhibitor N:(omega)-nitro-L-arginine (100 microM). However, afferent and efferent arteriolar dilator responses to ACh were significantly enhanced during selective iNOS inhibition with 1 microM PBIT (40.1 +/- 0.7% and 25.2 +/- 1.3%, respectively). These results suggest that activation of iNOS by LPS increases the influence of nitric oxide on afferent and efferent arteriolar tone and impairs endothelium-dependent nitric oxide effects.

Renal interstitial concentration of adenosine during endotoxin shock

The present experiments were designed to measure the renal interstitial concentration of adenosine in an attempt to determine whether adenosine participates in the regulation of renal hemodynamics during endotoxin shock. The renal concentration of adenosine in response to lipopolysaccharide (LPS) administration was measured in anesthetized dogs using a microdialysis method. Renal hemodynamic responses to LPS were also determined with and without the adenosine A(1) receptor antagonist, (E)-(R)-1-[3-(2-phenylpyrazolo[1, 5-a]pyridin-3-yl)acryloyl]pyperidin-2-ylacetic acid (FK352). Intravenous administration of LPS (0.5 mg/kg) significantly decreased renal blood flow and mean arterial pressure. These parameters reached the minimum level at 5-10 min after the LPS administration and then returned to their respective preinjection levels. The renal interstitial concentration of adenosine increased from 118+/-18 to 381+/-46 nM. During treatment with FK352, LPS decreased renal blood flow and mean arterial pressure, however, these reductions were significantly attenuated. LPS also increased adenosine concentration, but its rise was reduced along with the attenuation of LPS-induced renal blood flow reduction. These results suggest that adenosine was involved in LPS-induced renal hemodynamic changes and that FK352 has a protective effect against renal dysfunction during endotoxin shock. Since the adenosine concentration was inversely proportional to renal blood flow levels, it can be assumed that adenosine plays an important role as a mediator, but not as an initiator of renal hemodynamic changes during endotoxin shock.

Effect of beta(2)-adrenoceptor activation and angiotensin II on tumour necrosis factor and interleukin 6 gene transcription in the rat renal resident macrophage cells

This study aimed to examine whether lipopolysaccharide (LPS)-induced increase in tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) gene transcription was regulated by beta-adrenoceptor activation and whether TNF-alpha and IL-6 gene transcription was regulated by angiotensin II in rat renal resident macrophage cells. The cells were transfected with a fusion gene with the 5'-flanking region of rat TNF-alpha or IL-6 genes linked to a luciferase coding sequence as a reporter. The stimulatory effect of LPS on TNF-alpha transcription was suppressed by isoproterenol (10(-8)-10(-5)M) in a dose-dependent manner, whereas IL-6 transcription was only decreased by the high concentration (10(-5)M) of isoproterenol. The addition of beta(2)-adrenoceptor antagonist (ICI118,551), but not a beta(1)-adrenoceptor antagonist (atenolol), blocked the inhibitory effect of isoproterenol. By contrast, angiotensin II (10(-8)-10(-5)M) enhanced IL-6 gene transcription in the cells in a dose-dependent manner which was inhibited by type 1 angiotensin II receptor antagonist (CV11,974). TNF-alpha and IL-6 secretion from the cells was altered with beta(2)-adrenoceptor agonists (terbutaline, formoterol) and angiotensin II corresponding to changes of TNF-alpha and IL-6 gene transcription. Angiotensin II had no effect on TNF-alpha secretion and gene transcription. These findings suggested that beta(2)-adrenoceptor agonist and angiotensin II potentially could influence renal immune function through the regulation of TNF-alpha and IL-6 gene transcription by the renal resident macrophage cells.

Nitric oxide generation mediates lipid A-induced oxidant injury in renal proximal tubules

In previous studies, we found that lipid A, the biologically active component of lipopolysaccharide, triggers a rapid release of intracellular calcium, the activation of nitric oxide synthase (NOS), and nitric oxide (NO) production in rat proximal tubules. This pathway leads ultimately to cell death [as measured by the release of lactate dehydrogenase (LDH)], initiated by early generation of NO. In the present studies we found that lipid A produces a time- and concentration-dependent increase in lipid peroxidation [malondialdehyde (MDA) formation] prior to cell death. Furthermore, preventing lipid peroxidation protected against cell death. Lipid A (50 micro;g/ml) produced significant MDA formation in 30 min. The addition of two antioxidants 5 min prior to lipid A completely inhibited MDA formation and LDH release at 90 min. Preincubation with 5 mm GSH also significantly reduced MDA formation. The involvement of NOS activation in lipid A-induced lipid peroxidation was established when an NOS inhibitor and an inhibitor of intracellular calcium release completely blocked MDA formation. In addition, superoxide generation was significantly increased in the presence of lipid A, and the involvement of superoxide was established when superoxide dismutase protected against oxidant injury. The iron chelators deferoxamine (also a scavenger of peroxynitrite) and diethylenetriaminepentaacetic acid prevented lipid A-induced lipid peroxidation and cell death, indicating a role for iron and peroxynitrite. The addition of an NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl, prior to lipid A also completely protected tubule cells from lipid peroxidation and subsequent cell death. These results indicate that lipid A-stimulated NO generation in the rat proximal tubule initiates oxidant injury.

Renal gluconeogenesis and blood flow during endotoxic shock

OBJECTIVES

To determine whether endotoxic shock decreases the renal gluconeogenic capacity and the renal artery blood flow.

METHODS

An in-vivo, murine, nonrecirculating kidney perfusion model was studied in a trauma research laboratory. Each of 12 fasted, male Holtzman rats (shock n = 6, control n = 6) was injected with 1 mL of normal saline or endotoxin (20 mg/kg). Five hours after the injection, all the rats were anesthetized and blood samples were obtained for the determination of the plasma glucose. Right renal artery blood flow was measured by an ultrasonic small-animal flow meter. The kidney was then perfused via the renal artery with 37 degrees C, oxygenated, glucose-free Krebs-Henseleit solution in the presence of 100 mumol of phloridzin to inhibit the cellular uptake of glucose. Renal glucose production was determined by measuring glucose in both renal vein effluent and urine. After 30 minutes of equilibration, 5 mmol of lactate and 0.5 mmol of pyruvate were added to the perfusate as a gluconeogenic substrate. Renal vein and ureteral effluent samples were collected after 5, 10, and 15 minutes.

RESULTS

The endotoxic shock group showed hypoglycemia (p < 0.05) as well as a decrease in renal artery blood flow (p < 0.05). Gluconeogenic stimulation was demonstrable in both the control and the endotoxic shock groups after 15 minutes of perfusion with substrate (p < 0.05). However, renal gluconeogenesis was significantly attenuated in the endotoxic shock group compared with the control.

CONCLUSIONS

Renal glucose production in response to a gluconeogenic substrate is significantly attenuated during the hypoglycemic phase of endotoxic shock. Endotoxic shock also causes a significant decrease of renal artery blood flow.

Antioxidants attenuate endotoxin-induced acute renal failure in rats

Acute kidney dysfunction, manifested by a reduction in renal blood flow and in the glomerular filtration rate, is a common finding in septic shock. The pathogenetic mechanisms responsible for the renal dysfunction observed in the endotoxemic murine model are not completely understood. In this study, an attempt was made to halt the progressive renal dysfunction in the rats by administration of the antioxidants dimethylthiourea (DMTU) (50 mg/100 g) and superoxide dismutase (SOD) (0.4 mg/100 g) before endotoxin infusion (0.5 mg/100 g), or by inducing endotoxin tolerance. Renal function, assessed by creatinine, inulin, and p-aminohippuric acid clearance, nicotinamide adenine dinucleotide, and electrolyte reabsorption, was measured 4 hours after the endotoxin infusion. Renal function declined in all rats throughout the study period. However, the reduction in renal function was markedly slower in endotoxemic rats administered DMTU and SOD compared with untreated rats. Similar results were found following induction of endotoxin tolerance. These data suggest that DMTU, SOD, and endotoxin tolerance may be potentially beneficial in halting progressive renal damage associated with endotoxemia.

Renal impairment after spontaneous bacterial peritonitis in cirrhosis: incidence, clinical course, predictive factors and prognosis

Although spontaneous bacterial peritonitis is considered a precipitating factor of renal impairment in cirrhosis, no study specifically addressing this problem has been reported. This study was aimed at assessing the incidence, clinical course, predictive factors and prognosis of renal impairment in cirrhotic patients with peritonitis. Therefore, 252 consecutive episodes of spontaneous bacterial peritonitis in 197 patients were analyzed. Clinical and laboratory data obtained before and after diagnosis of peritonitis were considered as possible predictors of renal impairment and hospital mortality. Renal impairment occurred in 83 (33%) episodes, and in every instance it fulfilled the criteria of functional kidney failure. Renal impairment was progressive in 35 episodes, steady in 27 and transient in 21. Blood urea nitrogen and serum sodium concentration before peritonitis and band neutrophils count in blood at diagnosis were independent predictors for the development of renal impairment. Renal impairment was the strongest independent predictor of mortality during hospitalization. Other independent prognostic factors were blood urea nitrogen level before peritonitis, age, positive ascitic fluid culture and serum bilirubin level during infection. These results indicate that renal impairment is a frequent event in cirrhotic patients with spontaneous bacterial peritonitis that occurs mainly in patients with kidney failure before infection. Renal impairment is the most important predictor of hospital mortality in cirrhotic patients with spontaneous bacterial peritonitis.

Renal effects of intermittent versus continuous infusion of ibuprofen in the primate

The clinical use of nonsteroidal anti-inflammatory drugs is gaining wide acceptance and acute oliguric renal failure in association with the administration of ibuprofen has been reported. This study was designed to evaluate the renal effects of intermittent versus continuous intravenous infusion of ibuprofen (Motrin) over a 24-h period in the anesthetized non-pregnant baboon. A total of 50 mg/kg of ibuprofen was either infused continuously or given as a bolus in four divided doses (intermittent). Control animals received only normal saline. Mean aortic pressure showed a tendency to decrease with time in all groups studied with a significant decrease occurring in the infusion group. There were no significant changes in the renal artery flow, renal resistance, central venous pressure and heart rate within the groups. Serum urea nitrogen decreased and was significantly different from the baseline value at 24 h in the infusion group. Serum creatinine, however, showed no such changes. Although, urinary output and creatinine clearance showed a tendency to decrease in the treated groups, it was not significantly different. Plasma renin activity decreased from 9.95 to 2.3 ng/ml/hr in the control group but showed no significant changes in others. Serum levels of angiotensin converting enzyme were well maintained. The circulating levels of ibuprofen reached a steady state after 2 h in the infusion group. The results of this study demonstrate that continuous infusion of ibuprofen does not possess an advantage over its intermittent administration. Despite the modifications we have observed in renal flow and function, this drug appears to be safe in the dose levels we have used in these experiments.

Lipid A stimulates phospholipase D activity in rat mesangial cells via a G-protein

Stimulation of mesangial cells (MC) with the bacterial endotoxin Lipid A activated two enzymes involved in lipid metabolism. First, a phospholipase D hydrolyses phosphatidylethanolamine (PE) to phosphatidic acid (PA), followed by dephosphorylation of PA to 1,2-diacylglycerol (DAG) by PA phosphohydrolase. MC or microsomes from these cells were pre-labelled with [3H]glycerol. A 30-60 s stimulation with 10-100 ng of Lipid A/ml caused a decrease in [3H]glycerol in PE and increased radioactive glycerol in PA. The enzyme responsible for this hydrolysis preferred PE containing unsaturated acyl side chains. DAG was formed from PA within the first 1 min after Lipid A stimulation. Microsomes incubated with 25 mM-NaF to inhibit phospholipase C and to stimulate GTP-binding proteins also caused PE to be converted into PA. The [3H]glycerol and acyl mass of phosphatidylcholine, phosphatidylserine and phosphatidylinositol did not change with either Lipid A or NaF. Addition of guanosine 5'-[gamma-thio]triphosphate to MC microsomes caused the rapid decrease in proportion of PE and increase in PA, followed by an increase in DAG unsaturated acyl mass. These data suggest the concurrent G-protein-dependent activation by Lipid A of a PE-directed phospholipase D and a PA phosphohydrolase.

Role of neutrophil derived oxidants and elastase in lipopolysaccharide-mediated renal injury

Gram-negative bacterial sepsis is frequently associated with acute renal failure but the specific effects of lipopolysaccharide (LPS) and other bacterial products on kidney function are not known. Since either LPS or formyl-methionyl-leucyl-phenylalanine (FMLP)--a chemotactic peptide from bacterial cell walls--activate neutrophils (PMN) to release a number of potentially toxic factors in vitro, we determined the effect of adding PMN with LPS and/or FMLP to isolated perfused rat kidneys. Isolated rat kidneys perfused with LPS alone or LPS and normal PMN had normal glomerular filtration rates (GFR) and tubular Na reabsorption (TNa). Kidneys perfused with FMLP alone or FMLP and normal PMN also had normal GFR and TNa. In contrast, addition of PMN with both FMLP and LPS caused progressive renal dysfunction. For example, after 60 minutes of perfusion, GFR was reduced from 610 +/- 31 to 147 +/- 17 microliters/min/g and TNa from 97 +/- 1 to 72 +/- 2%, both P less than 0.01. Perfusion with the O2 metabolite scavengers catalase or dimethylthiourea afforded no protection while perfusion with the neutrophil elastase inhibitor Eglin C conferred substantial, but not complete, protection: GFR 492 +/- 34 microliters/min/g; TNa 91 +/- 3%. However, perfusion with both Eglin C and catalase completely prevented the toxic effects of LPS and FMLP-treated PMN on renal function. We conclude that in isolated kidneys, 1) the toxic effects of LPS requires FMLP-treated PMN and that 2) LPS and FMLP treated PMN cause progressive renal injury which is mediated by both O2 metabolites and neutrophil elastase.

Tumor necrosis factor alpha activates soluble guanylate cyclase in bovine glomerular mesangial cells via an L-arginine-dependent mechanism

Endothelium-derived nitric oxide (NO) causes vasodilatation by activating soluble guanylate cyclase, and glomerular mesangial cells respond to NO with elevations of intracellular guanosine 3',5'-cyclic monophosphate (cGMP). We explored whether mesangial cells can be stimulated to produce NO and whether NO modulates mesangial cell function in an autocrine or paracrine fashion. Tumor necrosis factor alpha (TNF-alpha) raised mesangial cell cGMP levels in a time- and concentration-dependent manner (threshold dose 1 ng/ml, IC50 13.8 ng/ml, maximal response 100 ng/ml). TNF-alpha-induced increases in mesangial cGMP content were evident at 8 h and maximal at 18-24 h. The TNF-alpha-induced stimulation of mesangial cell cGMP production was abrogated by actinomycin D or cycloheximide suggesting dependence on new RNA or protein synthesis. Hemoglobin and methylene blue, both known to inhibit NO action, dramatically reduced TNF-alpha-induced mesangial cell cGMP production. Superoxide dismutase, known to potentiate NO action, augmented the TNF-alpha-induced effect. Ng-monomethyl-L-arginine (L-NMMA) decreased cGMP levels in TNF-alpha-treated, but not vehicle-treated mesangial cells in a concentration-dependent manner (IC50 53 microM). L-arginine had no effect on cGMP levels in control or TNF-alpha-treated mesangial cells but reversed L-NMMA-induced inhibition. Interleukin 1 beta and lipopolysaccharide (LPS), but not interferon gamma, also increased mesangial cell cGMP content. Transforming growth factor beta 1 blunted the mesangial cell response to TNF-alpha. TNF-alpha-induced L-arginine-dependent increases in cGMP were also evident in bovine renal artery vascular smooth muscle cells, COS-1 cells, and 1502 human fibroblasts. These findings suggest that TNF-alpha induces expression in mesangial cell of an enzyme(s) involved in the formation of L-arginine-derived NO. Moreover, the data indicate that NO acts in an autocrine and paracrine fashion to activate mesangial cell soluble guanylate cyclase. Cytokine-induced formation of NO in mesangial and vascular smooth muscle cells may be implicated in the pathogenesis of septic shock.

Renal function and glomerular hemodynamics in male endotoxemic rats

The renal effects of a single intravenous dose of two different E. coli lipopolysaccharides (LPS 0111:B4 and LPS 0127:B8), at the same dose of 100 micrograms/kg, were evaluated in euvolemic Munich-Wistar (MW) rats by whole kidney clearance techniques and micropuncture studies. Following LPS infusion, a significant decrease (8%) in mean BP was observed only in the LPS 0127:B8 treated group. Inulin clearance fell 57% (LPS 0111:B4), P less than 0.01, and 38% (LPS 0127:B8), P less than 0.01. Para-aminohippuric (PAH) clearance decreased 31% (P less than 0.01) and total effective renal vascular resistance rose 70% (P less than 0.03) in response to LPS 0111:B4. No significant change in PAH clearance was noted in the LPS 0127:B8 group. Superficial single nephron glomerular filtration rate (SNGFR) was reduced 69% (LPS 0111:B4), P less than 0.03, and 33% (LPS 0127:B8), P less than 0.02. Superficial glomerular plasma flow fell 48% (LPS 0111:B4), P less than 0.03, and 24% (LPS 0127:B8), P less than 0.03. Both lipopolysaccharides were associated with an increase in afferent arteriolar resistance (RA) which accounted for a reduction in the glomerular capillary hydraulic pressure (PGC). There was no change in the proximal tubular pressure in either group and, therefore, the net transcapillary hydraulic pressures were reduced. No measurable change in the ultrafiltration coefficient. Kf, was observed in either group. In a second set of protocols, the effect of prior administration of indomethacin or captopril on LPS 0111:B4 action was investigated. A significant decrease in BP occurred when animals were pretreated with captopril. Both indomethacin and captopril prevented the renal effects of LPS 0111:B4.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of anti-lipid A human monoclonal antibody on lipopolysaccharide-induced toxicity to the kidney

Studies were done to evaluate the effects of the human monoclonal anti-lipid A IgM antibody A6(H4C5) on several components of the hemodynamic and renal toxicity of the cell wall lipopolysaccharide of E. coli 0111:B4. Antibody (0.25 to four mg./kg. BW) was administered 0.5 hour before, or premixed for one hour with, lipopolysaccharide (0.05 mg./kg., a 14 to 18% lethal dose), and the following measurements made over 0.5 to 3.5 hours of study: systemic arterial blood pressure, renal plasma flow, and glomerular filtration. The proximal tubular cell cytotoxicity of 90 mg./kg. of the cephalosporin cephaloridine was also quantified in similarly treated animals sacrificed 48 hours later. While one mg./kg. of antibody prevented the reduction by the lipopolysaccharide of renal plasma flow, it did not prevent the nephrotoxic synergy with cephaloridine, and four times the antibody dose did not prevent lipopolysaccharide-induced hypotension or reduced glomerular filtration. These amounts of this antibody protect leukopenic rabbits against the lethality of the slow onset bacteremic model of Pseudomonas conjunctivitis. It is suggested that the incompleteness of protection in this study may be the result of the sensitivity of the assay methods used and/or the acute endotoxemia produced in these animals.

Involvement of a pertussis toxin-sensitive G-protein-coupled phospholipase A2 in lipopolysaccharide-stimulated prostaglandin E2 synthesis in cultured rat mesangial cells

E. coli lipopolysaccharide (LPS) stimulated a dose- and time-dependent release of prostaglandin E2 (PGE2) in cultured rat glomerular mesangial cells. Pertussis toxin, an inhibitor of several GTP-binding proteins (G proteins), blocked nearly 80% of the LPS-stimulated PGE2 formation, while having virtually no effect on calcium ionophore-stimulated PGE2 production. We tested the possibility that a G protein-coupled activation of phospholipase A2 mediated the LPS-stimulated PGE2 production. Evidence for LPS activation of phospholipase A2 included a time-dependent LPS-induced generation of [32P]lysophosphatidylcholine and the inhibitory effects of a phospholipase A2 inhibitor, mepacrine, on LPS-induced PGE2 formation. Possible roles for phospholipase C-dependent activation of PGE2 synthesis by LPS seemed unlikely, as LPS did not elevate the cytosolic free calcium concentration or augment the appearance of water-soluble inositol phosphates. We conclude that LPS-induced PGE2 synthesis in rat glomerular mesangial cells is mediated through a G-protein-coupled phospholipase A2 activation. The activation of phospholipase A2 releases arachidonic acid and stimulates PGE2 synthesis preferentially, thereby improving glomerular hemodynamic events in endotoxemia.

Activation of glomerular mesangial cells by gram-negative bacterial cell wall components

The cell walls of gram-negative bacteria contain several biologically active components, including lipopolysaccharide (LPS), lipoprotein, and protein 1. The effects of these individual components and a synthetic analog of lipoprotein, TPP, on several activation parameters of glomerular mesangial cells (MC) were examined. Prostaglandin secretion, synthesis of the autogrowth factor, mesangial interleukin-1 (IL-1), and new synthesis of cellular proteins were assessed as markers of MC activation. All bacterial cell wall components evaluated were active in varying degrees as stimulants of prostaglandin secretion. In general, PGE was the predominant product. TPP and protein 1 also induced substantial secretion of thromboxane. Each cell-wall component was effective in stimulating mesangial IL-1 secretion. The activation of MC was associated with the enhanced synthesis of many cellular proteins in addition to IL-1. Stimulation by these bacterial components was dependent on the state of the mesangial cell cycle, because nonproliferating cells did not respond to these factors. Activation of MC by gram-negative bacterial cell wall components, with release of vasoactive prostaglandins and peptide mitogens, may be responsible for some of the glomerular hemodynamic alterations and cellular proliferative events associated with sepsis or chronic bacterial infection.

Neuropeptide Y prevents the blood pressure fall induced by endotoxin in conscious rats with adrenal medullectomy

Neuropeptide Y (NPY) is a vasoconstrictor peptide known to be present in the adrenal medulla, the terminal nerve endings, and in plasma. This study was designed to test whether NPY could prevent the acute blood pressure fall induced by endotoxin administration. Normotensive rats were subjected to adrenal demedullation on the right side and were either adrenalectomized or sham-operated on the left side. Eight to ten days later, NPY (0.07 microgram/min i.v.) or its vehicle were infused for 95 minutes into these conscious, semirestrained rats. The same experiments were performed with rats that received an infusion of epinephrine (0.1 microgram/min). These doses of NPY and epinephrine when given alone had no blood pressure effect. During the last 75 minutes of the 95-minute infusion, endotoxin (lipopolysaccharide Escherichia coli 0.111:B4, 10 micrograms/min i.v.) or its vehicle were administered. In rats with an intact adrenal gland, endotoxin failed to induce hypotension. In rats lacking a functioning adrenal medulla, however, endotoxin induced a pronounced mean blood pressure fall of 55 +/- 11.6 mm Hg (mean +/- SEM). This blood pressure drop could be prevented equally well with NPY and with epinephrine infusion and averaged 11 +/- 2.3 and 16 +/- 2.4 mm Hg, respectively, at the end of the experiment. Additional rats were biadrenalectomized and supplemented with an excess of glucocorticoids and mineralocorticoids. In these rats also, NPY markedly attenuated the blood pressure fall resulting from endotoxemia. These data taken together indicate that in conscious rats with no adrenal medulla, the acute blood pressure fall induced by endotoxin administration is greatly enhanced.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute renal failure in six horses resulting from haemodynamic causes

Six horses had been admitted to the hospital because of illness other than renal failure; diarrhoea, myositis, abdominal pain and/or suspected bacterial sepsis. Hypotension and disseminated intravascular coagulopathy were frequent findings in the horses. Abnormally high serum creatinine concentration and urine specific gravity of less than 1.022 were found in the horses with acute renal failure. Hyponatraemia and hypochloraemia were the most common abnormal electrolyte findings. Pronounced hyperkalaemia was not found. Variable degrees of tubular necrosis were seen in three of the four horses that had kidney sections submitted for microscopic examination. Renal cortical necrosis occurred in one horse. Intravenous fluid and electrolyte replacement was the most important therapy in those cases that were non-oliguric. Furosemide, mannitol and dopamine were used in horses with oliguria. The prognosis was generally good if the predisposing cause could be corrected and the acute renal failure was not oliguric.

Current perspectives on septic shock

Although septic shock may be initiated by invading microbes, it is the metabolic and immunologic host responses that determine the true pathophysiology of this common critical care illness. Currently, septic shock therapeutics emphasize empiric and symptomatic treatment. Biochemical elucidation of the septic process will ultimately result in specific interventions for this ominous intensive care syndrome.

Roles for thromboxane A2 and leukotrienes in endotoxin-induced acute renal failure

Bolus i.v. administration of 100 micrograms/kg of E. Coli lipopolysaccharide endotoxin (LPS) to adult male Munich-Wistar rats (N = 18) resulted in a progressive fall in RBF and GFR from 6.9 +/- 0.2 SE and 1.1 +/- 0.05 ml/min to minimal values at 50 minutes of 3.8 +/- 0.4 and 0.32 +/- 0.08 (P less than 0.05), respectively, without a fall in mean arterial pressure. At 50 minutes, renal cortical generation rates of PGE2 (1075 +/- 108 pg/mg tissue), 6 keto PGF1 alpha (221 +/- 41 pg/mg), and TxB2 (106 +/- 12 pg/mg) were significantly higher than those of vehicle-treated control rats (N = 10, PGE2 = 466 +/- 107, 6 keto PGF1 alpha = 94 +/- 3, and TxB2 = 35 +/- 3 pg/mg), and morphologic examination revealed normal histology with notable absence of leukocytes and platelets. Pretreatment of a third group of nine rats with TxA2 synthetase inhibitor UK-37.248 (dazoxiben, 10 mg/kg) selectively abolished the LPS-induced rise in TxB2 (29 +/- 3 pg/mg), but not PGE2 (837 +/- 62 pg/mg) or 6 keto PGF1 alpha (179 +/- 5 pg/mg), prevented the fall in RBF at 50 minutes (6.3 +/- 0.4 ml/min), and allowed for significant preservation of GFR (0.67 +/- 0.08 ml/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Considerations in the therapy of septic shock

In summary, gram-negative sepsis is unique among infectious illnesses in that it is a disorder that recruits endogenous physiologic processes to mediate tissue injury. This host damage frequently occurs in the absence of microbial invasion of affected organs. The resultant hypotension, coagulation defects, and organ dysfunction may be associated with serious morbidity or may contribute to mortality. Ultimately, however, mortality in patients with septic shock depends on the nature of the infectious process and the severity of the underlying illnesses. Unfortunately, attempts to aggressively treat septic patients with a formidable array of antimicrobial and pharmaceutical agents have not remarkably reduced mortality. Nor does it seem likely that future elucidation of the inflammatory mechanisms of sepsis will lead to the generation of therapeutic agents that will significantly improve survival. On the other hand, prophylactic or therapeutic modalities that deter colonization or invasion by pathogenetic organisms or that alter the ability of pathogens to evoke adverse host responses may be more likely to impact on the incidence and morbidity of gram-negative bacillary infections. Until modifications in the initial interactions of gram-negative pathogens with human hosts can be realized, the mortality of gram-negative sepsis is likely to remain high.

Renal hemodynamic effects of therapeutic plasma levels of sulindac sulfide during hemorrhage

There is continued debate over any renal sparing effects of sulindac (S): such a property would be of benefit and be unique among nonsteroidal anti-inflammatory drugs (NSAIDS). S undergoes a distinct metabolism whereby the active drug (sulindac sulfide (SS)) does not appear in the urine. Accordingly, we tested the effect of a plasma concentration of SS in the therapeutic range on renal blood flow (RBF), glomerular filtration rate (GFR), and renal prostaglandin (PG) concentrations during sudden renal ischemic stress. The ischemic stress was produced by a 15 to 20% reduction in arterial pressure by arterial hemorrhage (H) in four separate groups of anesthetized dogs: control, SS (0.4 mg/kg i.v. bolus followed by 0.03 mg/kg/min constant infusion), indomethacin (I, 10 mg/kg), and benoxaprofen (B, 75 mg/kg). A plasma concentration of 3.69 micrograms/ml of SS was achieved by the infusion, and no SS appeared in the urine. H reduced GFR (by 46%) and RBF (by 38%) in control dogs; in SS-treated dogs, a 60% decline in GFR and a 73% decrease in RGF occurred. These decreases in renal hemodynamics in the SS group during H were significantly greater than in the control group. Further, these decrements in GFR and RBF were similar to those observed in the I- and B-treated dogs. Finally, SS reduced baseline arterial and renal PG concentrations, and prevented any increase in renal PG release during H. Thus, we conclude that a concentration of SS in the therapeutic range, which does not appear in the urine, is capable of enhancing the decline in GFR and RBF during a sudden ischemic stress such as H.

Low-dose dopamine preserves renal blood flow in endotoxin shocked dogs treated with ibuprofen

Drugs that inhibit prostaglandin (PG) biosynthesis improve hemodynamics and survival in experimental endotoxic and septic shock. The therapeutic utility of these agents in the management of septic patients may be limited, however, by their tendency to decrease renal blood flow (RBF) in animals and humans stressed by experimental manipulations or disease states that promote renal vasoconstriction. In the present study, we addressed this question: can low-dose intravenous (iv) dopamine (4 micrograms/kg/min), a known renal vasodilator, improve renal perfusion in endotoxin-shocked dogs treated with the PG synthesis inhibitor, ibuprofen. RBF was measured in pentobarbital anesthetized dogs using an electromagnetic flow meter. After obtaining baseline hemodynamics, Escherichia coli endotoxin (1.5 mg/kg) was given iv. The dogs were randomized 30 min later into three groups: Group I received saline; Group II received ibuprofen (12.5 mg/kg, iv); Group III received ibuprofen plus dopamine. Comparison of Groups I and II revealed that ibuprofen increased mean arterial pressure (MAP) and systemic vascular resistance (SVR) (P less than 0.0001 and P = 0.002, respectively) and decreased RBF (P = 0.019). Adding low-dose dopamine (Group II vs Group III) did not significantly affect MAP or SVR, but did augment RBF (P less than 0.001). We conclude that low-dose dopamine improves renal hemodynamics in ibuprofen-treated endotoxemic dogs.

Measurement of urine prostaglandin E2 as a predictor of acute renal transplant rejection: preliminary findings

A radioimmunoassay for prostaglandin E2 (PGE2) in urine was developed and validated. It was used to provide serial measurements in eight renal transplant patients. Urine PGE2 concentration was increased between 1 and 7 days before any changes in the conventional biochemical indicators of acute rejection, serum creatinine and creatinine clearance. The increases in PGE2 concentration varied from 3 to 50 times that of the previous day. These results suggest that measurement of urinary PGE2 may be useful as an early indicator of acute renal transplant rejection.

Effects of nonsteroidal anti-inflammatory drugs on renal function in septic dogs

The effects of nonsteroidal anti-inflammatory drugs on renal function were studied in 15 chronically instrumented, unanesthetized beagles. In 9 dogs, bacterial peritonitis was induced by implanting in the peritoneal cavity a fibrin clot containing viable Escherichia coli. Six (control) dogs were subjected to laparotomy but were not implanted with an infected clot. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were estimated using standard clearance methods. All measurements were performed after resuscitation with Ringer's lactate to a pulmonary capillary wedge pressure of 6 Torr. When measured 24 hr after laparotomy, there were no significant changes (relative to baseline) in GFR or ERPF in either the septic or control groups. In septic dogs, 60 min after the administration of either indomethacin (2 mg/kg) or ibuprofen (25 mg/kg), GFR decreased an average of 26 +/- 11 ml/min (P = 0.043) and ERPF decreased an average of 100 +/- 27 ml/min (P = 0.02). In controls, administration of indomethacin (2 mg/kg) did not significantly affect either GFR or ERPF. These results suggest that renal function should be carefully monitored in clinical trials of nonsteroidal anti-inflammatory drugs in septic patients.

Diuresis and respiratory distress syndrome: physiologic mechanisms and therapeutic implications

Previous studies have suggested that spontaneous diuresis may be important to the recovery from respiratory distress syndrome in preterm infants. Daily quantification of fluid intake (1) and urine output (O) were recorded, and O/I and alveolar-arterial oxygen gradients (AaDO2) were determined for sequential eight-hour periods in 10 inborn premature infants with RDS. Sequential timed-urine-plasma collections were obtained during the first four days of life to evaluate the role of hormonal and vasoactive factors in the acute phase of RDS. Diuresis (O/I greater than 0.80) occurred at 25 to 32 hours, preceded any significant improvement in AaDO2 (which occurred at 57 to 64 hours), and was associated with a 6.2 +/- 1.4% decrease in body weight. Although there was no significant change in glomerular filtration rate, plasma AVP concentrations, or urinary excretion of AVP in the infants, there were significant decreases in both plasma concentrations and urinary excretion of 6-keto-PGF1 alpha (stable metabolite of prostacyclin) in sequential studies. These results suggest that changes in renal function or AVP may not be of primary importance in the diuresis associated with RDS, and that decreasing levels of prostacyclin, a prostaglandin that increases vascular permeability and lowers blood pressure, may have an important physiologic role.

Raised plasma thromboxane B2 levels in alcoholic liver disease

In experimental animals endotoxin administration causes increased levels of thromboxane B2 and prostaglandins. Liver cirrhosis is often complicated by endotoxemia. In sixteen patients with alcoholic liver cirrhosis, we measured plasma thromboxane B2 levels. In twelve patients we found on one or more occasions raised plasma thromboxane B2 levels. Raised plasma thromboxane B2 levels were associated with significantly higher serum levels of urea, alkaline phosphatase, gamma glutamyl transpeptidase and lower antiplasmin and antithrombin III levels. It is possible that some of the complications in patients with alcoholic liver cirrhosis are mediated by thromboxanes.