The impact of short term, long term and intermittent E. coli infection on male C57BL/6J mouse prostate histology and urinary physiology

Prostatic inflammation and prostatic fibrosis are associated with lower urinary tract dysfunction in men. Prostatic inflammation arising from a transurethral uropathogenic E. coli infection is sufficient to increase prostatic collagen content in male mice. It is not known whether and how the sequence, duration and chronology of prostatic infection influence urinary function, prostatic inflammation and collagen content. We placed a transurethral catheter into adult male C57BL/6J mice to deliver uropathogenic E. coli UTI189 two-weeks prior to study endpoint (to evaluate the short-term impact of infection), 10-weeks prior to study endpoint (to evaluate the long-term impact of infection), or two-, six-, and ten-weeks prior to endpoint (to evaluate the impact of repeated intermittent infection). Mice were catheterized the same number of times across all experimental groups and instilled with sterile saline when not instilled with E. coli to control for the variable of catheterization. We measured bacterial load in free catch urine, body weight and weight of bladder and dorsal prostate; prostatic density of leukocytes, collagen and procollagen 1A1 producing cells, and urinary function. Transurethral E. coli instillation caused more severe and persistent bacteriuria in mice with a history of one or more transurethral instillations of sterile saline or E. coli. Repeated intermittent infections resulted in a greater relative bladder wet weight than single infections. However, voiding function, as measured by the void spot assay, and the density of collagen and ProCOL1A1+ cells in dorsal prostate tissue sections did not significantly differ among infection groups. The density of CD45+ leukocytes was greater in the dorsal prostate of mice infected two weeks prior to study endpoint but not in other infection groups compared to uninfected controls.

Relevance of dog as an animal model for urologic diseases

We utilize animal models in urologic research to improve understanding of urinary physiology, determine the etiology of many urologic diseases, and discover and test novel therapeutic interventions. Dogs have a similar urinary tract anatomy and physiology to human and they develop many urologic diseases spontaneously. This chapter offers detailed comparisons of urinary tract anatomy, physiology, and the most common urologic diseases between humans and dogs. Dogs offer a unique opportunity for urologic research because they can be studied in research colonies and in client owned cohorts. Dogs also are among a limited number of non-human species that require continence and socially appropriate urinary behaviors (ex. going to the bathroom outside, training to not have submissive urination, etc.). These features make dogs unique in the animal kingdom and make them an ideal animal model for urologic research.

A retrospective review of canine benign prostatic hyperplasia with and without prostatitis

Benign prostatic hyperplasia (BPH) is the most common prostatic disorder in older intact male dogs, but despite its prevalence, there are inconsistencies in clinical diagnosis and treatment. Although prostate size was historically considered the hallmark feature of BPH in men, currently, there is only a weak correlation between prostate size and clinical severity. We performed a retrospective cohort study with the primary objective of assessing clinical signs, ultrasonographic findings, treatments, and outcomes in dogs diagnosed with BPH, with and without concurrent prostatitis. We reviewed medical records and obtained data on presenting signs, prostatic imaging, and prevalence of concurrent bacteriuria. Prostate size was determined by ultrasonography and compared to the calculated expected size based on patient age and weight. Treatment and outcome were described for the cases with a minimum 2 months follow-up. Median age of dogs diagnosed with BPH was 8 years. Clinical signs were present in 16/25 dogs and scored as mild to moderate (median Zambelli's Symptom Index for BPH score 12). The median prostatic volume to body mass ratio was 1.60 mm³/kg. Prostate size did not correlate with the symptom severity. Concurrent bacteriuria was confirmed in 4/25 cases via bacterial culture and/or cytology. Treatments pursued and responses were only available in a subpopulation of dogs (n = 9) and were highly variable. Studies are needed to determine if current treatment options for BPH in dogs resolve associated clinical signs in addition to reducing prostate size.

Osteopontin Deficiency Ameliorates Prostatic Fibrosis and Inflammation

Fibrogenic and inflammatory processes in the prostate are linked to the development of lower urinary tract symptoms (LUTS) in men. Our previous studies identified that osteopontin (OPN), a pro-fibrotic cytokine, is abundant in the prostate of men with LUTS, and its secretion is stimulated by inflammatory cytokines potentially to drive fibrosis. This study investigates whether the lack of OPN ameliorates inflammation and fibrosis in the mouse prostate. We instilled uropathogenic E. coli (UTI89) or saline (control) transurethrally to C57BL/6J (WT) or Spp1^tm1Blh/J (OPN-KO) mice and collected the prostates one or 8 weeks later. We found that OPN mRNA and protein expression were significantly induced by E. coli-instillation in the dorsal prostate (DP) after one week in WT mice. Deficiency in OPN expression led to decreased inflammation and fibrosis and the prevention of urinary dysfunction after 8 weeks. RNAseq analysis identified that E. coli-instilled WT mice expressed increased levels of inflammatory and fibrotic marker RNAs compared to OPN-KO mice including Col3a1, Dpt, Lum and Mmp3 which were confirmed by RNAscope. Our results indicate that OPN is induced by inflammation and prolongs the inflammatory state; genetic blockade of OPN accelerates recovery after inflammation, including a resolution of prostate fibrosis.

Genetic background but not prostatic epithelial beta-catenin influences susceptibility of male mice to testosterone and estradiol-induced urinary dysfunction

Urinary voiding dysfunction in aging men can cause bothersome symptoms and irreparable tissue damage. Underlying mechanisms are not fully known. We previously demonstrated that subcutaneous, slow-release testosterone and estradiol implants (T+E2) drive a pattern of urinary voiding dysfunction in male mice that resembles that of aging men. The initial goal of this study was to test the hypothesis that prostatic epithelial beta-catenin (Ctnnb1) is required for T+E2-mediated voiding dysfunction. Targeted Ctnnb1 deletion did not significantly change voiding function in control or T+E2 treated mice but led to the surprising discovery that the C57BL/6J × FVB/NJ × 129S1 mixed genetic background onto which Ctnnb1 loss of function alleles were maintained is profoundly susceptible to voiding dysfunction. The mixed background mice develop a more rapid T+E2-mediated increase in spontaneous urine spotting, are more impaired in ability to initiate bladder contraction, and develop larger and heavier bladders than T+E2 treated C57BL/6J pure bred mice. To better understand mechanisms, we separately evaluated contributions of T and E2 and found that E2 mediates voiding dysfunction. Our findings that genetic factors serve as modifiers of responsiveness to T and E2 demonstrate the need to control for genetic background in studies of male voiding dysfunction. We also show that genetic factors could control severity of voiding dysfunction. We demonstrate the importance of E2 as a key mediator of voiding impairment, and show that the concentration of E2 in subcutaneous implants determines the severity of voiding dysfunction in mice, demonstrating that the mouse model is tunable, a factor which is important for future pharmacological intervention studies.

Clinical profiles of post-load glucose subgroups and their association with glycaemic traits over time: An IMI-DIRECT study

AIM

To examine the hypothesis that, based on their glucose curves during a seven-point oral glucose tolerance test, people at elevated type 2 diabetes risk can be divided into subgroups with different clinical profiles at baseline and different degrees of subsequent glycaemic deterioration.

METHODS

We included 2126 participants at elevated type 2 diabetes risk from the Diabetes Research on Patient Stratification (IMI-DIRECT) study. Latent class trajectory analysis was used to identify subgroups from a seven-point oral glucose tolerance test at baseline and follow-up. Linear models quantified the associations between the subgroups with glycaemic traits at baseline and 18 months.

RESULTS

At baseline, we identified four glucose curve subgroups, labelled in order of increasing peak levels as 1-4. Participants in Subgroups 2-4, were more likely to have higher insulin resistance (homeostatic model assessment) and a lower Matsuda index, than those in Subgroup 1. Overall, participants in Subgroups 3 and 4, had higher glycaemic trait values, with the exception of the Matsuda and insulinogenic indices. At 18 months, change in homeostatic model assessment of insulin resistance was higher in Subgroup 4 (β = 0.36, 95% CI 0.13-0.58), Subgroup 3 (β = 0.30; 95% CI 0.10-0.50) and Subgroup 2 (β = 0.18; 95% CI 0.04-0.32), compared to Subgroup 1. The same was observed for C-peptide and insulin. Five subgroups were identified at follow-up, and the majority of participants remained in the same subgroup or progressed to higher peak subgroups after 18 months.

CONCLUSIONS

Using data from a frequently sampled oral glucose tolerance test, glucose curve patterns associated with different clinical characteristics and different rates of subsequent glycaemic deterioration can be identified.

A uropathogenic E. coli UTI89 model of prostatic inflammation and collagen accumulation for use in studying aberrant collagen production in the prostate

Bacterial infection is one known etiology of prostatic inflammation. Prostatic inflammation is associated with prostatic collagen accumulation and both are linked to progressive lower urinary tract symptoms in men. We characterized a model of prostatic inflammation using transurethral instillations of Escherichia coli UTI89 in C57BL/6J male mice with the goal of determining the optimal instillation conditions, understanding the impact of instillation conditions on urinary physiology, and identifying ideal prostatic lobes and collagen 1a1 prostatic cell types for further analysis. The smallest instillation volume tested (50 µL) distributed exclusively to the bladder, 100- and 200-µL volumes distributed to the bladder and prostate, and a 500-µL volume distributed to the bladder, prostate, and ureter. A threshold optical density of 0.4 E. coli UTI89 in the instillation fluid was necessary for significant (P < 0.05) prostate colonization. E. coli UTI89 infection resulted in a low frequency, high volume spontaneous voiding pattern. This phenotype was due to exposure to E. coli UTI89, not catheterization alone, and was minimally altered by a 50-µL increase in instillation volume and doubling of E. coli concentration. Prostate inflammation was isolated to the dorsal prostate and was accompanied by increased collagen density. This was partnered with increased density of protein tyrosine phosphatase receptor type C+, procollagen type I-α1+ copositive cells and decreased density of α2-smooth muscle actin+, procollagen type I-α1+ copositive cells. Overall, we determined that this model is effective in altering urinary phenotype and producing prostatic inflammation and collagen accumulation in mice.

An immunohistochemical prostate cell identification key indicates that aging shifts procollagen 1A1 production from myofibroblasts to fibroblasts in dogs prone to prostate-related urinary dysfunction

Background

The identity and spatial distribution of prostatic cell types has been determined in humans but not in dogs, even though aging- and prostate-related voiding disorders are common in both species and mechanistic factors, such as prostatic collagen accumulation, appear to be shared between species. In this publication we characterize the regional distribution of prostatic cell types in the young intact dog to enable comparisons with human and mice and we examine how the cellular source of procollagen 1A1 changes with age in intact male dogs.

Methods

A multichotomous decision tree involving sequential immunohistochemical stains was validated for use in dog and used to identify specific prostatic cell types and determine their distribution in the capsule, peripheral, periurethral and urethral regions of the young intact canine prostate. Prostatic cells identified using this technique include perivascular smooth muscle cells, pericytes, endothelial cells, luminal, intermediate, and basal epithelial cells, neuroendocrine cells, myofibroblasts, fibroblasts, fibrocytes, and other hematolymphoid cells. To enhance rigor and transparency, all high resolution images (representative images shown in the figures and biological replicates) are available through the GUDMAP database at https://doi.org/10.25548/16-WMM4.

Results

The prostatic peripheral region harbors the largest proportion of epithelial cells. Aging does not change the density of hematolymphoid cells, fibroblasts, and myofibroblasts in the peripheral region or in the fibromuscular capsule, regions where we previously observed aging- and androgen-mediated increases in prostatic collagen abundance Instead, we observed aging-related changes the procollagen 1A1 positive prostatic cell identity from a myofibroblast to a fibroblast.

Conclusions

Hematolymphoid cells and myofibroblasts are often identified as sources of collagen in tissues prone to aging-related fibrosis. We show that these are not the likely sources of pathological collagen synthesis in older intact male dogs. Instead, we identify an aging-related shift in the prostatic cell type producing procollagen 1A1 that will help direct development of cell type and prostate appropriate therapeutics for collagen accumulation.

Impact of sex, androgens, and prostate size on C57BL/6J mouse urinary physiology: urethral histology

The National Institutes of Health leveled new focus on sex as a biological variable with the goal of understanding sex-specific differences in health and physiology. We previously published a functional assessment of the impact of sex, androgens, and prostate size on C57BL/6J mouse urinary physiology (Ruetten H, Wegner KA, Zhang HL, Wang P, Sandhu J, Sandhu S, Mueller B, Wang Z, Macoska J, Peterson RE, Bjorling DE, Ricke WA, Marker PC, Vezina CM. Am J Physiol Renal Physiol 317: F996-F1009, 2019). Here, we measured and compared five characteristics of urethral histology (urethral lumen diameter and area, epithelial cell count, epithelial and rhabdosphincter thickness, epithelial cell area, and total urethral area) in male and female 9-wk-old C57BL/6J mice using hematoxylin and eosin staining. We also compared male mice with castrated male mice, male and female mice treated with the steroid 5α-reductase inhibitor finasteride or testosterone, or male mice harboring alleles (Pbsn4^cre/+; R26R^Dta/+) that reduce prostate lobe mass. The three methods used to reduce prostate mass (castration, finasteride, and Pbsn4^cre/+; R26R^Dta/+) changed urethral histology, but none feminized male urethral histology (increased urethral epithelial area). Exogenous testosterone caused increased epithelial cell count in intact females but did not masculinize female urethral histology (decrease epithelial area). Our results lay a critical foundation for future studies as we begin to parse out the influence of hormones and cellular morphology on male and female urinary function.

Prostate epithelial-specific expression of activated PI3K drives stromal collagen production and accumulation

We genetically engineered expression of an activated form of P110 alpha, the catalytic subunit of PI3K, in mouse prostate epithelium to create a mouse model of direct PI3K activation (Pbsn-cre4Prb;PI3K^GOF/+ ). We hypothesized that direct activation would cause rapid neoplasia and cancer progression. Pbsn-cre4Prb;PI3K^GOF/+ mice developed widespread prostate intraepithelial hyperplasia, but stromal invasion was limited and overall progression was slower than anticipated. However, the model produced profound and progressive stromal remodeling prior to explicit epithelial neoplasia. Increased stromal cellularity and inflammatory infiltrate were evident as early as 4 months of age and progressively increased through 12 months of age, the terminal endpoint of this study. Prostatic collagen density and phosphorylated SMAD2-positive prostatic stromal cells were expansive and accumulated with age, consistent with pro-fibrotic TGF-β pathway activation. Few reported mouse models accumulate prostate-specific collagen to the degree observed in Pbsn-cre4Prb;PI3K^GOF/+ . Our results indicate a signaling process beginning with prostatic epithelial PI3K and TGF-β signaling that drives prostatic stromal hypertrophy and collagen accumulation. These mice afford a unique opportunity to explore molecular mechanisms of prostatic collagen accumulation that is relevant to cancer progression, metastasis, inflammation and urinary dysfunction. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Insight and Resources From a Study of the "Impact of Sex, Androgens, and Prostate Size on C57BL/6J Mouse Urinary Physiology

The purpose of this symposium report is to summarize information from a session 3 oral presentation at the Society of Toxicologic Pathology Annual Symposium in Raleigh, North Carolina. Mice are genetically tractable and are likely to play an important role in elucidating environmental, genetic, and aging-related mechanisms of urinary dysfunction in men. We and others have made significant strides in developing quantitative methods for assessing mouse urinary function and our collaborators recently showed that aging male mice, like men, develop urinary dysfunction. Yet, it remains unclear how mouse prostate anatomy and histology relate to urinary function. The purpose of this report is to share foundational resources for evaluating mouse prostate histology and urinary physiology from our recent publication "Impact of Sex, Androgens, and Prostate Size on C57BL/6J Mouse Urinary Physiology: Functional Assessment." We will begin with a review of prostatic embryology in men and mice, then move to comparative histology resources, and conclude with quantitative measures of rodent urinary physiology.

Impact of sex, androgens, and prostate size on C57BL/6J mouse urinary physiology: functional assessment

Laboratory mice are used to identify causes of urinary dysfunction including prostate-related mechanisms of lower urinary tract symptoms. Effective use of mice for this purpose requires a clear understanding of molecular, cellular, anatomic, and endocrine contributions to voiding function. Whether the prostate influences baseline voiding function has not been specifically evaluated, in part because most methods that alter prostate mass also change circulating testosterone concentrations. We performed void spot assay and cystometry to establish a multiparameter "baseline" of voiding function in intact male and female 9-wk-old (adult) C57BL/6J mice. We then compared voiding function in intact male mice to that of castrated male mice, male (and female) mice treated with the steroid 5α-reductase inhibitor finasteride, or male mice harboring alleles (Pbsn4^cre/+; R26R^Dta/+) that significantly reduce prostate lobe mass by depleting prostatic luminal epithelial cells. We evaluated aging-related changes in male urinary voiding. We also treated intact male, castrate male, and female mice with exogenous testosterone to determine the influence of androgen on voiding function. The three methods used to reduce prostate mass (castration, finasteride, and Pbsn4^cre/+; R26R^Dta/+) changed voiding function from baseline but in a nonuniform manner. Castration feminized some aspects of male urinary physiology (making them more like intact female mice) while exogenous testosterone masculinized some aspects of female urinary physiology (making them more like intact male mice). Our results provide evidence that circulating testosterone is responsible in part for baseline sex differences in C57BL/6J mouse voiding function while prostate lobe mass in young, healthy adult mice has a lesser influence.

Prostatic collagen architecture in neutered and intact canines

BACKGROUND

Prostate stiffness and increased collagen content both associate with the presence of urinary symptoms in men but mechanisms responsible, including impact of age and androgens, are unknown. Dogs develop prostate-related urinary dysfunction similar to humans, but mechanisms are also unknown. Mice have been used to examine how prostatic collagen accumulation affects voiding but whether mouse prostatic collagen organization resembles human or dog has not been evaluated. Here, we have constructed the first comprehensive, comparative maps of collagen architecture in canine, human, and mouse prostate and test whether canine prostatic collagen content is increased by aging and reduced by castration.

METHODS

Complete transverse prostate sections were stained with picrosirius red and imaged with confocal microscopy to reveal and compare collagen architecture across species. Canine prostatic collagen fiber length, diameter, and density in prostatic urethral, periurethral, peripheral, and capsular regions were quantified and compared among four experimental groups: young intact, young neutered, old intact, and old neutered dogs.

RESULTS

Surprisingly, the majority of collagen was localized to the prostatic urethra in canine, human, and mouse. In canine and human, capsular regions also featured a dense collagen network but it appeared less dense than around prostatic urethra. Older, intact male canines exhibited overall denser prostate collagen fibers and had thicker capsular fibers than young, intact males. Prostatic glandular regions undergo dramatic atrophy and regression following castration, and our finding of neutered animals having increased collagen fiber density in both periurethral and peripheral regions is consistent with glandular contraction and increased proportion of stroma.

CONCLUSIONS

Collagen architecture in dog appears similar to that in humans when cross sections are compared side-by-side. Canine collagen organization is affected by both age and androgen status, suggesting these factors may contribute to collagen accumulation in some males.

Inhibition of caspase-3 improves contractile recovery of stunned myocardium, independent of apoptosis-inhibitory effects

OBJECTIVES

The aim of this study was to investigate whether the caspase-3 inhibitor Ac-DEVD-CHO functionally improves stunned myocardium.

BACKGROUND

Degradation of troponin I contributes to the pathogenesis of myocardial stunning, whereas the role of apoptosis is unknown. Caspase-3 is an essential apoptotic protease that is specifically inhibited by Ac-DEVD-CHO.

METHODS

Isolated working hearts of rats were exposed to 30 min of low-flow ischemia, followed by 30 min of reperfusion. Ac-DEVD-CHO (0.1 to 1 micromol/l) was added 15 min before ischemia/reperfusion or 5 min before reperfusion. Cardiac output, external heart power, left ventricular (LV) developing pressure and contractility (dp/dt(max)) were measured. Apoptosis was assessed by TUNEL staining and internucleosomal deoxyribonucleic acid fragmentation. Caspase-3 processing and troponin I cleavage were determined by immunoblotting. Caspase-3 activity was measured using a fluorogenic substrate.

RESULTS

The addition of Ac-DEVD-CHO before ischemia/reperfusion or before reperfusion dose-dependently and significantly (p < 0.05) improved post-ischemic recovery of cardiac output, external heart power, LV developing pressure and dp/dt(max), compared with the vehicle (0.01% dimethyl sulfoxide). Ac-DEVD-CHO was similarly effective when given before reperfusion. Ac-DEVD-CHO blocked ischemia/reperfusion-induced caspase-3 activation, but cardiomyocyte apoptosis was unaffected. Troponin I cleavage was not inhibited by Ac-DEVD-CHO.

CONCLUSIONS

Caspase-3 is activated in stunned myocardium. Inhibition of caspase-3 by Ac-DEVD-CHO significantly improves post-ischemic contractile recovery of stunned myocardium, even when given after the onset of ischemia. The mechanism(s) of protection by Ac-DEVD-CHO appear to be independent of apoptosis. Inhibition of caspase-3 is a novel therapeutic strategy to improve functional recovery of stunned myocardium.

Effects of the cardioselective KATP channel blocker HMR 1098 on cardiac function in isolated perfused working rat hearts and in anesthetized rats during ischemia and reperfusion

It has been argued that activation of KATP channels in the sarcolemmal membrane of heart muscle cells during ischemia provides an endogenous cardioprotective mechanism. In order to test whether the novel cardioselective KATP channel blocker HMR 1098 affects cardiac function during ischemia, experiments were performed in rat hearts during ischemia and reperfusion. Isolated perfused working rat hearts were subjected to 30 min of low-flow ischemia in which the coronary flow was reduced to 10% of its control value, followed by 30-min reperfusion. In the first set of experiments the hearts were electrically paced at 5 Hz throughout the entire protocol. At the end of the 30-min ischemic period the aortic flow had fallen to 44 +/- 2% (n=8) of its nonischemic value in vehicle-treated hearts, whereas in the presence of 0.3 micromol/l and 3 micromol/l HMR 1098 it had fallen to 29 +/- 7% (n=5, not significant) and 8 +/- 2% (n=12, P<0.05), respectively. Glibenclamide (3 micromol/l) reduced the aortic flow to 9.5 +/- 7% (n=4, P<0.05). In control hearts the QT interval in the electrocardiogram shortened from 63 +/- 6 ms to 36 +/- 4 ms (n=10, P<0.05) within 4-6 min of low-flow ischemia. This shortening was completely prevented by 3 micromol/l HMR 1098 (60 +/- 5 ms before ischemia, 67 +/- 6 ms during ischemia, n=9, not significant). When rat hearts were not paced, the heart rate fell spontaneously during ischemia, and HMR 1,098 (3 micromol/l) caused only a slight, statistically non-significant reduction in aortic flow during the ischemic period. In order to investigate whether HMR 1098 shows cardiodepressant effects in a more pathophysiological model, the left descending coronary artery was occluded for 30 min followed by reperfusion for 60 min in anesthetized rats. Treatment with HMR 1098 (10 mg/kg i.v.) had no statistically significant effects on mean arterial blood pressure and heart rate during the control, ischemia and reperfusion periods. At the end of the reperfusion period, aortic blood flow was slightly reduced by HMR 1098, without reaching statistical significance (two-way analysis of ANOVA, P=0.15). Myocardial infarct size as a percentage of area at risk was not affected by HMR 1098 (vehicle: 75 +/- 3%, HMR 1098: 72 +/- 2%, n=7 in each group). In conclusion, cardiodepressant effects of HMR 1098 were observed only in isolated perfused working rat hearts which were continuously paced during global low-flow ischemia. In the model of anesthetized rats subjected to regional ischemia, HMR 1098 had no significant effect on cardiac function or infarct size.

Cardiovascular abnormalities with normal blood pressure in tissue kallikrein-deficient mice

Tissue kallikrein is a serine protease thought to be involved in the generation of bioactive peptide kinins in many organs like the kidneys, colon, salivary glands, pancreas, and blood vessels. Low renal synthesis and urinary excretion of tissue kallikrein have been repeatedly linked to hypertension in animals and humans, but the exact role of the protease in cardiovascular function has not been established largely because of the lack of specific inhibitors. This study demonstrates that mice lacking tissue kallikrein are unable to generate significant levels of kinins in most tissues and develop cardiovascular abnormalities early in adulthood despite normal blood pressure. The heart exhibits septum and posterior wall thinning and a tendency to dilatation resulting in reduced left ventricular mass. Cardiac function estimated in vivo and in vitro is decreased both under basal conditions and in response to beta-adrenergic stimulation. Furthermore, flow-induced vasodilatation is impaired in isolated perfused carotid arteries, which express, like the heart, low levels of the protease. These data show that tissue kallikrein is the main kinin-generating enzyme in vivo and that a functional kallikrein-kinin system is necessary for normal cardiac and arterial function in the mouse. They suggest that the kallikrein-kinin system could be involved in the development or progression of cardiovascular diseases.

Inhibition of endogenous nitric oxide synthase potentiates ischemia-reperfusion-induced myocardial apoptosis via a caspase-3 dependent pathway

OBJECTIVE

Apoptosis of cardiomyocytes may contribute to ischemia-reperfusion injury. The role of nitric oxide (NO) in apoptosis is controversial. Therefore, we investigated the effect of NO synthase inhibition on apoptosis of cardiomyocytes during ischemia and reperfusion and elucidated the underlying mechanisms.

METHODS AND RESULTS

Isolated perfused rat hearts (n = 6/group) were subjected to ischemia (30 min) and reperfusion (30 min) in the presence or absence of the NO synthase inhibitor NG-mono-methyl-L-arginine. Reperfusion induced cardiomyocyte apoptosis as assessed by immunohistochemistry (TUNEL-staining) and the demonstration of the typical DNA laddering. Apoptosis during reperfusion was associated with the cleavage of caspase-3, the final down-stream executioner caspase, whereas the protein levels of the anti-apoptotic protein Bcl-2 and the pro-apoptotic protein Bax were unchanged. Inhibition of the NO synthase drastically increased ischemia and reperfusion-induced apoptosis of cardiomyocytes. Moreover, the NO synthase inhibitor enhanced the activation of caspase-3, suggesting that NO interferes with the activation of caspases in ischemia-reperfusion.

CONCLUSION

The results of the present study demonstrate that inhibition of endogenous NO synthesis during ischemia and reperfusion leads to an enhanced induction of apoptosis, suggesting that the endogenous NO synthesis protects against apoptotic cell death. Inhibition of NO synthesis thereby activates the caspase cascade, whereas the Bcl-2/Bax protein levels remained unchanged.

Release of nitric oxide from endothelial cells stimulated by YC-1, an activator of soluble guanylyl cyclase

1 In this study we examined the endothelium-dependent effect of YC-1 - a benzyl indazole derivative which directly activates soluble guanylyl cyclase (sGC) - on vascular relaxation and nitric oxide (NO) and guanosine-3',5'-cyclic monophosphate (cyclic GMP) in endothelial cells. 2 In preconstricted rat aortic rings with intact endothelium, YC-1 produced a concentration-dependent relaxation. However, the concentration response curve was shifted rightward to higher concentrations of YC-1, when (i) the aortas were pre-treated with L-NG-nitroarginine methylester (L-NAME) or (ii) the endothelium was removed. 3 Incubation of bovine aortic endothelial cells (BAEC) with YC-1 produced a concentration-dependent NO synthesis and release as assessed using a porphyrinic microsensor. Pre-incubating cells with L-NAME or with 8-bromo-cyclic GMP decreased this effect indicating that the YC-1 stimulation of NO synthesis is due to an activation of nitric oxide synthase, but not to an elevation of cyclic GMP. No direct effect of YC-1 on recombinant endothelial constitutive NO synthase activity was observed. 4 The YC-1 stimulated NO release was reduced by 90%, when extracellular free calcium was diminished. 5 In human umbilical vein endothelial cells (HUVEC), YC-1 stimulated intracellular cyclic GMP production in a concentration- and time-dependent manner. Stimulation of cyclic GMP was greater with a maximum concentration of YC-1 compared to calcium ionophore A23187. Similar effects were observed in BAEC and rat microvascular coronary endothelial cells (RMCEC). 6 When HUVEC and RMCEC were pre-treated with L-NG-nitroarginine (L-NOARG), the maximum YC-1 stimulated cyclic GMP increase was reduced by >/=50%. 7 These results indicate, that beside being a direct activator of sGC, YC-1 stimulates a NO-synthesis and release in endothelial cells which is independent of elevation of cyclic GMP but strictly dependent on extracellular calcium. The underlying mechanism needs to be determined further.

Downregulation of soluble guanylyl cyclase in young and aging spontaneously hypertensive rats

Endothelial dysfunction, as observed in hypertension and atherosclerosis, is associated with a reduction in the bioavailability of endothelium-derived nitric oxide (NO). We tested the hypothesis that alterations in the soluble guanylyl cyclase (sGC) pathway may also contribute to the pathogenesis of hypertension. Therefore, we investigated the expression and activity of sGC in young (6 weeks) and aging (17 months) spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto rats (WKY). Endothelium-independent relaxation of aortic rings in response to the sGC activator YC-1 was attenuated in SHR, and expression of both alpha(1) and beta(1) subunits of heterodimeric sGC and the basal contents of cGMP were reduced specifically in SHR aorta. Moreover, mRNA expression of the cGMP receptor and effector protein cGMP-dependent protein kinase type Ialpha (cGKIalpha) was also reduced. Interestingly, downregulation of both sGC and cGKIalpha expression was observed in young, ie, normotensive SHR, whereas impairment of the endothelium-independent relaxation was found only in aging SHR. Accordingly, similar cGMP levels were reached in response to YC-1 in young SHR and young WKY, suggesting a compensatory increased sensitivity or effectiveness of the sGC pathway in young SHR. In aging SHR, however, increased sensitivity to YC-1 no longer compensated for the impairment of endothelium-independent relaxation, suggesting that other mechanisms were involved. In fact, endothelium-independent relaxations were partially restored by superoxide dismutase, suggesting a pathophysiological role of superoxide production, particularly at later disease stages. Thus, tissue-specific downregulation of components of the sGC/cGMP pathway is an early event in the pathogenesis of hypertension.

Ramiprilat prevents the development of acute coronary endothelial dysfunction in the dog

We investigated the effect of an infusion of ramiprilat on the development of coronary endothelial dysfunction. In anesthetized dogs, the endothelium-dependent vasodilators acetylcholine (ACh, 5 and 10 microg x min(-1) for 1 min) and serotonin (5-HT, 50 and 100 microg x min(-1) for 1 min) and the endothelium-independent vasodilator nitroglycerin (NTG, 50 and 100 microg x min(-1) for 1 min) were given intracoronarily (i.c.) both prior to and after 60 min of ischemia (I) and 180 min of reperfusion (R) of a coronary artery. During I/R the dogs received i.c. either saline (N = 22) or ramiprilat (40 ng/kg x min(-1), N = 14). At the end of the experiment, a biopsy of the most distal coronary bed was processed for scanning electron microscopy (SEM). Prior to I/R all vasodilators induced a similar dose-related increase in coronary flow in both groups. Following I/R, in controls the responses to ACh and 5-HT were significantly blunted (ACh: -39% and -34%; 5-HT: -48% and -49%); those to NTG were unchanged. Ramiprilat significantly prevented the blunting of the responses to ACh (-5%, and -10%) and 5-HT (-11%, and -19%). SEM of control subepicardial arterioles showed adhesion of leukocytes to the endothelium and crater formation. No craters were seen in the ramiprilat-treated dogs. Thus, an acute infusion of ramiprilat significantly prevents the development of coronary endothelial dysfunction. Additionally, the appearance of crater-like changes on the endothelial surface can be taken as a morphological marker of endothelial dysfunction.

Upregulation of ICAM-1 expression on J774.2 macrophages by endotoxin involves activation of NF-kappaB but not protein tyrosine kinase: comparison to induction of iNOS

This study compares the signal transduction pathway which leads to the upregulation of intercellular adhesion molecule-1 (ICAM-1) expression with that of the increase in the expression of inducible nitric oxide synthase (iNOS) protein and activity caused by endotoxin in cultured J774.2 macrophages. Treatment of J774.2 cells with lipopolysaccharide E. coli (LPS) induced a concentration-dependent increase in the expression of ICAM-1 on the cell surface within 4 h and an increase in iNOS protein and activity at 24 h. The upregulation of ICAM-1 expression on J774.2 macrophages caused by LPS was significantly inhibited by pretreatment of the cells with inhibitors of the activation of the nuclear transcription factor NF-kappaB, such as L-1-tosylamido-2-phenylethylchloromethyl ketone (TPCK), pyrrolidine dithiocarbamate (PDTC), rotenone or calpain inhibitor I, but not by the tyrosine kinase inhibitors, tyrphostin AG126 or genistein. In contrast, genistein or tyrphostin AG126 also prevented the induction of iNOS protein and activity in J774.2 macrophages elicited by LPS. Thus, the increase in the expression of ICAM-1 on J774.2 macrophages by endotoxin involves the activation of NFkappaB, but not of protein tyrosine kinase.

Reduction of myocardial reperfusion injury by an inhibitor of poly (ADP-ribose) synthetase in the pig

The effect of the Poly (adenosine 5'-diphosphate ribose) synthetase (PARS) inhibitor 3-aminobenzamide on (i) infarct size caused by regional myocardial ischaemia (60 min) and reperfusion (3 h) in the anaesthetised pig, and (ii) on the cell injury/necrosis of human cardiomyoblasts caused by hydrogen peroxide (3 mM) was investigated. Regional myocardial ischaemia and reperfusion resulted in an infarct size of 66+/-3% of the area at risk, which was reduced by 3-aminobenzamide (to 44+/-2%, n=6), but not 3-aminobenzoic acid (66+/-5%, n=4). 3-aminobenzamide also reduced the postischaemic contractile dysfunction. 3-aminobenzamide, but not 3-aminobenzoic acid, abolished the increase in PARS activity as well as the cell injury/necrosis caused by hydrogen peroxide in the cardiomyoblasts. In conclusion, the PARS inhibitor 3-aminobenzamide reduces myocardial reperfusion injury in the pig, and attenuates the cell injury and death associated with oxidant stress in human cardiomyoblasts. We propose that the activation of PARS plays an important role in the injury associated with oxidant stress of the heart.

Coronary endothelial dysfunction after ischemia and reperfusion in the dog: a functional and morphological investigation

Coronary endothelial dysfunction is characterized by a lower response to endothelium-dependent vasodilators such as acetylcholine (ACh) and serotonin (5HT), but by an unaltered response to endothelium-independent vasodilators such as nitroglycerin (NTG). In the present study, we investigated the vasoreactivity of the coronary bed in vivo, in a dog model of ischemia and reperfusion (I/R). We also assessed the morphology of the subepicardial arterioles and capillary bed by means of scanning electron microscopy (SEM). Anesthetized, instrumented dogs were divided in two groups. One group (N = 27) was submitted to ischemia (60 min) and reperfusion (180 min) of the left circumflex coronary artery, the second group (N = 8) was sham-operated. Prior to and following I/R, ACh, 5-HT, and NTG were given intracoronarily. At the end of the experiment a 1 cm3 myocardial biopsy was processed for SEM. The sham-operated dogs showed a reduction of basal coronary flow of 11%, but the vasoreactivity to ACh and 5-HT remained constant. In the I/R group, basal coronary flow was reduced by 35% (p < 0.05), and the vasoreactivity to ACh and 5-HT, but not to NTG, was significantly blunted. At SEM the arterioles of the dogs submitted to I/R showed a marked adhesion of leukocytes associated with holes on the endothelial surface, while the capillary bed was free of changes and patient. Thus, following I/R, coronary endothelial dysfunction could be demonstrated in vivo by the blunting of the vasoreactive responses to two different endothelium-dependent vasodilators. The responses to NTG were not affected, probably because the function of the smooth muscle cell was preserved, and the capillary bed was patent.

Endothelin-1 stimulates the biosynthesis of tumour necrosis factor in macrophages: ET-receptors, signal transduction and inhibition by dexamethasone

Endothelin-1 (ET-1) enhances the biosynthesis of interleukin-6 (IL-6) in endothelial cells and bone marrow-derived stromal cells of the rat. This study investigates (i) whether ET-1 stimulates the formation of tumour necrosis factor alpha (TNF alpha) or interferon-gamma (IFN gamma) in cultured macrophages or in the anaesthetized rat. Incubation of J774.2 macrophages with ET-1 (0.001-1 microM) caused a concentration- and time-dependent increase in the concentration of TNF alpha, but not of IFN gamma, in the culture medium. The increase in TNF alpha caused by stimulation of J774.2 macrophages was abolished by pretreatment of cells with (i) the protein synthesis inhibitor cycloheximide, (ii) with the selective ETA-receptor antagonists BQ-123 or BQ-485 (but not the selective ETB-receptor antagonist BQ-788), (iii) the tyrosine kinase inhibitors genistein or tyrphostin AG126, or (iv) with the glucocorticoid, dexamethasone. The inhibition by dexamethasone of the formation of TNF alpha by cells activated with ET-1 is not due to the formation of lipocortin-1 (LC1), as it was not reduced by a monoclonal antibody against LC1. Systemic administration (i.v.) of ET-1 (1 nmol.kg-1) to anaesthetized rats caused a rapid and sustained (maximum: 45 min; return to baseline: within 180 min) rise in the plasma levels of TNF alpha. This is the first demonstration that ET-1 can release proinflammatory cytokines in vitro and in vivo. The generation of TNF alpha caused by ET-1 involves (in sequence) the (i) activation of ETA-receptors, (ii) activation of tyrosine kinase resulting in the phosphorylation of intracellular proteins, (iii) the activation of, hitherto, unknown transcription factors, finally resulting in (iv) transcription and translation of the TNF alpha gene. The generation of TNF alpha by cells activated with ET-1 points to a pro-inflammatory role of ET-1 in diseases associated with local (e.g. atherosclerosis, heart failure) or systemic inflammation (circulatory shock), which are associated with high ET-1 plasma levels.

Interleukin-13 is a more potent inhibitor of the expression of inducible nitric oxide synthase in smooth muscle cells than in macrophages: a comparison with interleukin-4 and interleukin-10

This study compares the effects of interleukin (IL)-13, a cytokine with anti-inflammatory properties, with those of IL-4 or IL-10 on the expression of inducible nitric oxide synthase (iNOS) protein and activity in 1) a murine macrophage cell line (J774.2) activated with lipopolysaccharide (LPS) and 2) rat aortic smooth muscle cells (RASM) activated with LPS plus interferon-gamma. Pretreatment of macrophages with IL-4 or IL-13 caused a similar, concentration-dependent inhibition of the formation of nitrite and the expression of iNOS protein elicited by LPS. In contrast, IL-13 was a much more potent inhibitor of the formation of nitrite and the expression of iNOS protein in activated RASM than IL-4. IL-10 caused only a small, but significant, inhibition of the nitrite formation induced by LPS in macrophages and RASM. Pretreatment of J774.2 macrophages, but not of RASM, with the phosphatidylinositol-3-kinase inhibitor, wortmannin (10-100 nM), attenuated the inhibition by either IL-13 or IL-4 of the LPS-induced increase in nitrite in a dose-related fashion. Thus, IL-13 is more potent than IL-4 in preventing the expression of iNOS protein and activity in activated RASM, whereas IL-13 and IL-4 are equipotent in inhibiting the expression of iNOS protein and activity in J774.2 macrophages.

Combination immunotherapy which neutralises the effects of TNF alpha and IL-1 beta attenuates the circulatory failure and multiple organ dysfunction caused by endotoxin in the rat

Pro-inflammatory cytokines such as tumour necrosis factor-alpha (TNF alpha) or interleukin-1 beta (IL-1 beta) are implicated in the pathogenesis of septic shock. Here we investigate the role of endogenous TNF alpha and IL-1 beta on (i) the circulatory failure, (ii) the multiple organ dysfunction syndrome (MODS) and (iii) the induction of the inducible isoform of nitric oxide (NO) synthase (iNOS) caused by endotoxin (LPS) in the anaesthetised rat. Here we demonstrate that (i) a polyclonal antibody against TNF alpha, (ii) a polyclonal antibody against IL-1, (iii) co-administration of polyclonal antibodies against TNF alpha and IL-1 and (iv) neutralisation of the effects of both TNF alpha and IL-1 with one polyclonal antibody directed against both cytokines reduces the circulatory failure, the liver injury/dysfunction, the pancreatic injury (but not the renal dysfunction) caused by endotoxin in the rat. The beneficial effects of these interventions on haemodynamics and organ injury/dysfunction are most likely due to prevention of the induction of iNOS. The two different interventions which neutralised the effects of both TNF alpha and IL-1 were superior in reducing the circulatory failure and the organ injury caused by endotoxin in the rat, than single interventions aimed at neutralising the effects of either cytokine. Thus, we propose that interventions which are able to neutralise the effects of both TNF alpha and IL-1 (combination immunotherapy) may be of benefit in the treatment of patients with septic shock.

Effects of tyrphostins and genistein on the circulatory failure and organ dysfunction caused by endotoxin in the rat: a possible role for protein tyrosine kinase

1 Here we compared the effects of various inhibitors of the activity of protein tyrosine kinase on (i) the expression of the activity of the inducible isoform of nitric oxide (NO) synthase (iNOS) caused by endotoxin (lipopolysaccharide, LPS) in cultured macrophages, (ii) the induction of iNOS and cyclooxygenase 2 (COX-2) protein and activity in rats with endotoxaemia, and (iii) the circulatory failure and organ dysfunction caused by LPS in the anesthetized rat. 2 Activation of murine cultured macrophages with LPS (1 microgram ml-1) resulted, within 24 h, in a significant increase in nitrite (an indicator of the formation of NO) in the cell supernatant. This increase in nitrate was attenuated by the tyrphostins AG126, AG556, AG490 or AG1641 or by genistein in a dose-dependent fashion (IC50: approximately 15 microM). In contrast, tyrphostin A1 (an analogue of tyrphostin AG126) or daidzein (an analogue of genistein) had no effect on the rise in nitrite caused by LPS. 3 Administration of LPS (E. coli, 10 mg kg-1, i.v.) caused hypotension and a reduction of the pressor responses elicited by noradrenaline (NA, 1 microgram kg-1, i.v.). Pretreatment of rats with the tyrphostins AG126, AG490, AG556, AG1641 or A1 attenuated the circulatory failure caused by LPS. Although genistein attenuated the vascular hyporeactivity to NA, it did not affect the hypotension caused by LPS. Daidzein did not affect the circulatory failure caused by LPS. 4 Endotoxaemia for 360 min resulted in rises in the serum levels of (i) urea and creatinine (indicators of renal failure), (ii) alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin and gamma-glutamyl transferase (gamma GT) (indicators of liver injury/dysfunction), lipase (an indicator of pancreatic injury) as well as lactate (an indicator of tissue hypoxia). None of the tyrosine kinase inhibitors tested had a significant effect on the rise i the serum levels of urea, but the tyrphostins AG126, AG556 or A1 significantly attenuated the rises in the serum level of creatinine caused by LPS. In addition, all tyrphostins and genistein attenuated the liver injury/failure, the pancreatic injury, the hypoglycaemia and the lactic acidosis caused by LPS. In contrast, daidzein did not reduce the organ injury/dysfunction or the lactic acidosis caused by LPS. 5 Injection of LPS resulted (within 90 min) in a substantial increase in the serum level of tumor necrosis factor alpha (TNF alpha), which was attenuated by pretreatment of LPS-rats with any of the tyrphostins used. Genistein, but not daidzein, also reduced the rise in the serum levels of TNF alpha caused by LPS. Endotoxaemia for 6 h also resulted in a substantial increase in the expression of iNOS and COX-2 protein and activity in the lung, which was attenuated by pretreatment of LPS-rats with the tyrphostins AG126, AG556 or genistein, but not by daidzein. 6 Thus, tyrphostins (AG126, AG556, AG1641 or A1) and genistein, but not daidzein (inactive analogue of genistein), prevent the (i) circulatory failure, (ii) the multiple organ dysfunction (liver and pancreatic dysfunction/injury lactacidosis, hypoglycaemia), as well as (iii) the induction of iNOS and COX-2 protein and activity in rats with endotoxic shock.

Effect of calpain inhibitor I, an inhibitor of the proteolysis of I kappa B, on the circulatory failure and multiple organ dysfunction caused by endotoxin in the rat

1. We compared the effects of calpain inhibitor I (inhibitor of the proteolysis of I kappa B and, hence, of the activation of nuclear factor kappa B (NF kappa B) and dexamethasone on (i) the circulatory failure, (ii) multiple organ dysfunction and (iii) induction of the inducible isoforms of nitric oxide (NO) synthase (iNOS) and cyclo-oxygenase (COX-2) in anaesthetized rats with endotoxic shock. 2. Injection of lipopolysaccharide (LPS, E. coli, 10 mg kg-1, i.v.) resulted in hypotension and a reduction of the pressor responses elicited by noradrenaline. This circulatory dysfunction was attenuated by pretreatment of LPS-rats with calpain inhibitor I (10 mg kg-1, i.v., 2 h before LPS) or dexamethasone (1 mg kg-1, i.v.). 3. Endotoxaemia also caused rises in the serum levels of (i) urea and creatinine (renal dysfunction), (ii) alanine aminotransferase (ALT), aspartate aminotransferase (AST) (hepatocellular injury), bilirubin and gamma-glutamyl transferase (gamma GT) (liver dysfunction), (iii) lipase (pancreatic injury) and (iv) lactate. Calpain inhibitor I and dexamethasone attenuated the liver injury, the pancreatic injury, the lactic acidosis as well as the hypoglycaemia caused by LPS. Dexamethasone, but not calpain inhibitor I, reduced the renal dysfunction caused by LPS. 4. Endotoxaemia for 6 h resulted in a substantial increase in iNOS and COX-2 protein and activity in lung and liver, which was attenuated in LPS-rats pretreated with calpain inhibitor I or dexamethasone. 5. Thus, calpain inhibitor I and dexamethasone attenuate (i) the circulatory failure, (ii) the multiple organ dysfunction (liver and pancreatic dysfunction/injury, lactic acidosis, hypoglycaemia), as well as (iii) the induction of iNOS and COX-2 protein and activity in rats with endotoxic shock. We propose that prevention of the activation of NF-kappa B in vivo may be useful in the therapy of circulatory shock or of disorders associated with local or systemic inflammation.

Effect of selective blockade of endothelin ETB receptors on the liver dysfunction and injury caused by endotoxaemia in the rat

1. We investigated the effects of the selective endothelin (ET)A receptor antagonist BQ-485 and the selective ETB receptor antagonist BQ-788 on circulatory failure, multiple organ dysfunction syndrome (MODS) and the alterations in acid base balance caused by endotoxaemia in the anaesthetized rat. 2. Male Wistar rats were anaesthetized (thiopentone sodium; 120 mg kg-1, i.p.) and received a continuous infusion of vehicle (saline, 0.6 ml kg-1h-1, i.v.), BQ-485 (10 nmol kg-1 min-1, i.v.) or BQ-788 (10 nmol kg-1 min-1, i.v.). Fifteen min later, animals received a bolus injection of either saline (0.9% NaCl, 1 ml kg-1, i.v.) or E. coli lipopolysaccharide (LPS, 10 mg kg-1, i.v.). 3. Injection of LPS resulted in a fall in blood pressure from 115 +/- 4 mmHg (time 0) to 82 +/- 4 mmHg at 360 min (n = 15) as well as a hyporeactivity to the pressor responses to noradrenaline (NA, 1 microgram kg-1, i.v.). Infusion of BQ-788 attenuated the delayed hypotension (at 360 min: 100 +/- 4 mmHg, n = 7; P < 0.05) and significantly enhanced the pressor responses elicited by NA (at 60 to 240 min). In contrast, treatment of LPS-rats with BQ-485 augmented the hypotension (at 360 min), but did not affect the vascular hyporeactivity elicited by endotoxaemia. 4. Endotoxaemia for 360 min resulted in rises in the serum levels of urea and creatinine (indicators of renal failure), glutamate-oxalate-transferase (GOT) and glutamate-pyruvate-transferase (GPT) (indicators of hepatocellular injury), and bilirubin and gamma-glutamyl transferase (gamma GT) (indicators of liver failure) as well as nitrite (indicator of the induction of nitric oxide synthase; iNOS). Treatment of LPS-rats with BQ-788, but not with BQ-485, attenuated the degree of liver injury and failure, while neither BQ-788 nor BQ-485 affected the acute renal failure or the induction of iNOS caused by endotoxin. 5. Endotoxaemia also caused (within 15 min) an acute metabolic acidosis (falls in pH, HCO3-and base excess) which was compensated by hyperventilation (fall in PaCO2). Treatment of LPS-rats with BQ-788 or BQ-485 did not affect the metabolic acidosis caused by LPS. 6. Thus, the selective ETB receptor antagonist BQ-788 attenuated (i) the delayed hypotension, (ii) the vascular hyporeactivity to NA as well as (iii) the degree of hepatocellular injury and dysfunction caused by endotoxin in the anaesthetized rat. In contrast, the selective ETA receptor antagonist did neither attenuate the circulatory failure nor the liver or renal dysfunction associated with endotoxaemia. We propose that the prevention of the hepatocellular dysfunction and injury caused BQ-788 in endotoxaemia is due to an improvement in oxygen delivery to the liver secondary to (i) inhibition of pre-sinusoidal constriction, (ii) inhibition of sinusoidal constriction, and (iii) improvement in perfusion pressure.

Prevention of the expression of inducible nitric oxide synthase by aminoguanidine or aminoethyl-isothiourea in macrophages and in the rat

An enhanced formation of nitric oxide (NO) following the induction of the inducible isoform of NOS (iNOS) has been implicated in the pathogenesis of circulatory shock and inflammation. This study elucidates the effects of the NOS inhibitors aminoethyl-isothiourea (AE-ITU), aminoguanidine (AG), NG-methyl-L-arginine (L-NMMA) or N omega-Nitro-L-arginine methyl ester (L-NAME) on the expression of iNOS protein lipopolysaccharide (LPS) in macrophages and the rat (lung homogenates). The expression of iNOS protein was detected by Western blot analysis using a specific iNOS antibody. In the absence of LPS, the iNOS protein was expressed neither in macrophages nor in the lung. LPS (1 microgram.ml-1) resulted in the expression of iNOS protein in macrophages, which was significantly inhibited by pretreatment of cells with AE-ITU or AG, but not by L-NMMA or L-NAME. In addition, LPS (10 mg.kg-1, i.v.) also caused an increase in the expression of iNOS protein in lungs obtained from rats at 6 h after LPS, which was significantly reduced by treatment of LPS-rats with AE-ITU or AG, but not with L-NMMA or L-NAME. Thus, AE-ITU or AG inhibit not only iNOS activity, but also the induction of iNOS protein in vitro and in vivo caused by endotoxin.

Effects of the endothelin receptor antagonist, SB 209670, on circulatory failure and organ injury in endotoxic shock in the anaesthetized rat

1. This study investigates the effects of the non-selective ETA/ETB receptor antagonist, SB 209670, on systemic haemodynamics, renal function, liver function, acid-base balance and survival in a rat model of endotoxic shock. 2. Injection of E. coli lipopolysaccharide (LPS, 10 mg kg-1, i.v.) resulted in increases in the serum levels of tumour necrosis factor-alpha (TNF-alpha, maximum 60 min after LPS), endothelin-1, (ET-1; maximum 120 min after LPS), and interferon-gamma (IFN-gamma, maximum 180 min after LPS). 3. Injection of LPS also resulted in a fall in blood pressure from 113 +/- 3 mmHg (time = 0) to 84 +/- 4 mmHg at 360 min (n = 15) as well as a hyporeactivity to the vasoconstrictor responses elicited by noradrenaline (NA, 1 microgram kg-1, i.v.). Pretreatment of rats with a continuous infusion of SB 209670 (3 mg kg-1, i.v. bolus + 100 micrograms kg-1, i.v. infusion commencing 15 min prior to LPS) significantly augmented the hypotension as well as the vascular hyporeactivity to NA caused by endotoxaemia. 4. Pretreatment of LPS-rats with SB 209670 (3 mg kg-1, i.v. bolus given 15 min prior to LPS) or infusion of SB 209670 (bolus dose and infusion as above) resulted in a reduction in 6 h-survival from 71% (control) to 30% and 13%, respectively. 5. Endotoxaemia for 4 h resulted in rises in the serum levels of urea and creatinine (indicators of renal failure), but not in the serum levels of bilirubin, GPT and GOT (indicators of liver dysfunction and/or hepatocellular injury). Pretreatment of LPS-rats with SB 209670 (3 mg kg-1, i.v. bolus 15 min prior to LPS) significantly augmented the serum levels of creatinine, bilirubin, GPT and GOT caused by endotoxin. In addition, endotoxaemia caused, within 15 min, an acute metabolic acidosis (falls in pH, HCO3- and base excess) which was compensated by hyperventilation (fall in PaCO2). Pretreatment of LPS-rats with SB 209670 (3 mg kg-1, i.v. bolus) significantly augmented the metabolic acidosis caused by LPS. 6. Thus, the non-selective ETA/ETB receptor antagonist, SB 209670, augments the degree of (i) hypotension, (ii) vascular hyporeactivity to noradrenaline, (iii) renal dysfunction and (iv) metabolic acidosis caused by endotoxin in the anaesthetized rat. In contrast to rats treated with LPS alone, LPS-rats treated with SB 209670 exhibited liver dysfunction and hepatocellular injury. We propose that the release of endogenous ET-1 serves to maintain blood pressure and subsequently organ perfusion in septic shock.

Attenuation of endotoxin-induced multiple organ dysfunction by 1-amino-2-hydroxy-guanidine, a potent inhibitor of inducible nitric oxide synthase

1. We have investigated the effects of (i) several guanidines on the activity of the inducible isoform of nitric oxide (NO) synthase (iNOS) in murine cultured macrophages and rat aortic vascular smooth muscle cells (RASM); and (ii) 1-amino-2-hydroxy-guanidine, the most potent inhibitor of iNOS activity discovered, on haemodynamics, multiple organ (liver, renal, and pancreas) dysfunction and iNOS activity in rats with endotoxic shock. 2. The synthesized guanidine analogues caused concentration-dependent inhibitions of the increase in nitrite formation caused by lipopolysaccaride (LPS, 1 microgram ml-1) in J774.2 macrophages and RASM cells with the following rank order of potency: 1-amino-2-hydroxy-guanidine > 1-amino-2-methyl-guanidine > 1-amino-1-methyl-guanidine > 1-amino-1,2-dimethyl-guanidine. Interestingly, 1-amino-2-hydroxy-guanidine (IC50: J774.2, 68 microM; RASM, 114 microM) was more potent in inhibiting nitrite formation caused by LPS than NG-methyl-L-arginine, but less potent than aminoethyl-isothiourea. 3. In the anaesthetized rat, LPS caused a fall in mean arterial blood pressure (MAP) from 115 +/- 4 mmHg (time 0) to 98 +/- 5 mmHg at 2 h (P < 0.05, n = 10) and 69 +/- 5 mmHg at 6 h (P < 0.05, n = 10). The pressor effect of noradrenaline (NA, 1 mg kg-1, i.v.) was also significantly reduced at 1 to 6 h after LPS (vascular hyporeactivity). Treatment of LPS-rats with 1-amino-2-hydroxy-guanidine (10 mg kg-1, i.v. plus 10 mg kg-1 h-1 starting at 2 h after LPS) prevented the delayed hypotension and vascular hyporeactivity seen in LPS-rats. However, 1-amino-2-hydroxy-guanidine had no effect on either MAP or the pressor effect elicited by NA in rats infused with saline rather than LPS. 4. Endotoxaemia for 6 h caused a significant rise in the serum levels of aspartate or alanine aminotransferase (i.e. GOT or GPT) and bilirubin, and hence, liver dysfunction. Treatment of LPS-rats with 1-amino-2-hydroxy-guanidine significantly attenuated the liver dysfunction caused by LPS (P < 0.05, n = 10). Injection of LPS also caused a rapid (almost maximal at 2 h) increase in the serum levels of urea and creatinine, and hence, renal dysfunction. This renal dysfunction was not affected by 1-amino-2-hydroxy-guanidine (P > 0.05; n = 10). Endotoxaemia also caused a dysfunction of pancreas (rise in serum levels of lipase) as well as a metabolic acidosis (falls in PCO2, HCO3 and base excess). Both pancreatic dysfunction and metabolic acidosis were largely attenuated by treatment of LPS-rats with 1-amino-2-hydroxy-guanidine. In rats infused with saline rather than LPS, 1-amino-2-hydroxy-guanidine had no effect on liver, renal or pancreatic function (n = 4). 5. Endotoxaemia for 6 h resulted in a rise in the serum levels of nitrite (11.0 +/- 0.8 microM, P < 0.01, n = 10), which was significantly reduced by 1-amino-2-hydroxy-guanidine (6.5 +/- 0.7 microM, P < 0.05, n = 10). Endotoxaemia for 6 h was also associated with a significant increase in iNOS activity in lung and liver, which was significantly reduced in lung or liver homogenates obtained from LPS-rats treated with 1-amino-2-hydroxy-guanidine. In addition, endotoxaemia for 6 h resulted in a significant increase in myeloperoxidase activity (MPO), an indicator of neutrophil infiltration, in the liver. Treatment of LPS-rats with 1-amino-2-hydroxy-guanidine did not affect the rise in MPO-activity in the liver caused by endotoxin. 6. Thus, 1-amino-2-hydroxy-guanidine is a potent inhibitor of iNOS activity in macrophages or RASM in culture as well as in rats with endotoxic shock. Inhibition of iNOS activity with 1-amino-2-hydroxy-guanidine prevents the delayed circulatory failure and attenuates the dysfunction of liver, and pancreas, as well as the metabolic acidosis caused by endotoxaemia.

Comparison of the effects of aminoguanidine and N omega-nitro-L-arginine methyl ester on the multiple organ dysfunction caused by endotoxaemia in the rat

This study compares the effects of aminoguanidine, a relatively selective inhibitor of inducible nitric oxide (NO) synthase, and N omega-nitro-L-arginine methyl ester (L-NAME), a selective inhibitor of endothelial NO synthase, on hypotension and multiple organ dysfunction caused by endotoxaemia in the anaesthetised rat. In the sham-operated rats, L-NAME, but not aminoguanidine, caused a dose-dependent increase in blood pressure. Endotoxin caused hypotension, increased in plasma nitrite (an indicator of inducible NO synthase activity), and dysfunction of kidney, liver and pancreas. Treatment of endotoxic rats with aminoguanidine or L-NAME caused significant and sustained rises in blood pressure. The increase in plasma nitrite caused by endotoxin was inhibited by aminoguanidine, but not by L-NAME. Aminoguanidine, but not L-NAME, attenuated the renal, liver and pancreatic dysfunction caused by endotoxaemia. Thus, selective inhibition of inducible (aminoguanidine), but not endothelial NO synthase (L-NAME) attenuates the circulatory failure and the multiple organ failure caused by endotoxaemia.

The multiple organ dysfunction syndrome caused by endotoxin in the rat: attenuation of liver dysfunction by inhibitors of nitric oxide synthase

1. We have investigated whether (i) endotoxaemia caused by E. coli lipopolysaccharide in the anaesthetized rat causes a multiple organ dysfunction syndrome (MODS; e.g. circulatory failure, renal failure, liver failure), and (ii) an enhanced formation of nitric oxide (NO) due to induction of inducible NO synthase (iNOS) contributes to the MODS. In addition, this study elucidates the beneficial and adverse effects of aminoethyl-isothiourea (AE-ITU), a relatively selective inhibitor of iNOS activity, and NG-methyl-L-arginine (L-NMMA), a non-selective inhibitor of NOS activity on the MODS caused by endotoxaemia. 2. In the anaesthetized rat, LPS caused a fall in mean arterial blood pressure (MAP) from 117 +/- 3 mmHg (time 0) to 97 +/- 4 mmHg at 2 h (P < 0.05, n = 15) and 84 +/- 4 mmHg at 6 h (P < 0.05, n = 15). The pressor effect of noradrenaline (NA, 1 micrograms kg-1, i.v.) was also significantly reduced at 1 to 6 h after LPS (vascular hyporeactivity). Treatment of LPS-rats with AE-ITU (1 mg kg-1, i.v. plus 1 mg kg-1 h-1 starting at 2 h after LPS) caused only a transient rise in MAP, but significantly attenuated the delayed vascular hyporeactivity seen in LPS-rats. Infusion of L-NMMA (3 mg kg-1, i.v. plus 3 mg kg-1 h-1) caused a rapid and sustained rise in MAP and attenuated the delayed vascular hyporeactivity to NA. Neither AE-ITU nor L-NMMA had any effect on either MAP or the pressor effect elicited by NA in rats infused with saline rather than LPS. 3. Endotoxaemia for 6 h was associated with a significant rise in the serum levels of aspartate or alanine aminotransferase (i.e. GOT or GPT), gamma-glutamyl-transferase (gamma GT), and bilirubin, and hence, liver dysfunction. Treatment of LPS-rats with AE-ITU significantly attenuated this liver dysfunction (rise in GOT, GPT, gamma GT and bilirubin) (P < 0.05, n = 10). In contrast, L-NMMA reduced the increase in the serum levels of gamma GT and bilirubin, but not in GOT and GPT (n = 5). Injection of LPS also caused a time-dependent, but rapid (almost maximal at 2 h), increase in the serum levels of urea and creatinine, and hence, renal dysfunction. This renal dysfunction was not affected by either AE-ITU (n = 10) or L-NMMA (n = 5). In rats infused with saline rather than LPS, neither AE-ITU (n = 4) nor L-NMMA (n = 4) had any significant effect on the serum levels of GOT, GPT, gamma GT, bilirubin, creatinine or urea. 4. Endotoxaemia for 6 h resulted in a 4.5 fold rise in the serum levels of nitrite (9.13 +/- 0.77 microM, P < 0.01, n = 15), which was significantly reduced by treatment with AE-ITU (6.32 +/- 0.48 microM, P < 0.05, n = 10) or L-NMMA (5.10 +/- 0.40 microM, P < 0.05, n = 5). In addition, endotoxaemia for 6 h was also associated with a significant increase in iNOS activity in lung and liver homogenates, which was significantly reduced in lung or liver homogenates obtained from LPS-rats treated with either AE-ITU or L-NMMA. 5. Thus, AE-ITU or L-NMMA (i) inhibits iNOS activity in LPS-rats without causing a significant increase in MAP in rats infused with saline and, hence inhibition of endothelial NOS activity, and (ii) attenuates the delayed circulatory failure as well as the liver dysfunction caused by endotoxaemia in the rat. Thus, an enhanced formation of NO may contribute to the development of liver failure in endotoxic shock.