Chronic pulmonary hypertension--the monocrotaline model and involvement of the hemostatic system

Inhibiting IL-6 in medicine: a new twist to sustain inhibition of his cytokine tin the therapy of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a chronic, progressive disease characterized by an increase in blood pressure in the lungs' arteries. It can occur in a variety of species, including humans, dogs, cats, and horses. To date, PAH has a high mortality rate in both veterinary and human medicine, often due to complications such as heart failure. The complex pathological mechanisms of PAH involve multiple cellular signalling pathways at various levels. IL-6 is a powerful pleiotropic cytokine that regulates several phases of immune response, inflammation, and tissue remodelling. The hypothesis of this study was that the use of an IL-6 antagonist in PAH could interrupt or mitigate the cascade of events that leads to the progression of the disease and the worsening of clinical outcome, as well as tissue remodelling. In this study, we used two pharmacological protocols with an IL-6 receptor antagonist in a monocrotaline-induced PAH model in rats. Our results showed that the use of an IL-6 receptor antagonist had a significant protective effect, ameliorating both haemodynamic parameters, lung and cardiac function, tissue remodelling, and the inflammation associated with PAH. The results of this study suggest that the inhibition IL-6 could be a useful pharmacological strategy in PAH, in both human and veterinary medicine.

Inflammation Intensifies Monocrotaline-Induced Liver Injury

Pyrrolizidine alkaloids (PAs) are the most common toxins of plant origin, and it is evident that PAs pollute soil, water, nearby plants, and derived foods. Cases of human poisoning due to ingestion of PA-contaminated foods have been reported in several countries. Monocrotaline (MCT) is a pyrrolizidine alkaloid from the plants of Crotalaria genus that causes hepatic and cardiopulmonary toxicities, and the exhibition of the toxicities requires the metabolic activation by CYP3A4 to form electrophilic dehydro-monocrotaline (DHM). The present study demonstrated that myeloperoxidase (MPO) also participated in the bioactivation of MCT. N-Chloromonocrotaline was detected in both HClO/MCT incubations and MPO/H2O2/MgCl2/MCT incubations. DHM-derived N-acetylcysteine (NAC) conjugates were detected in the above incubations fortified with NAC. Lipopolysaccharide-induced inflammation in mice resulted in an elevated level of hepatic MPO activity, increased metabolic activation of MCT, and intensified elevation of serum ALT and AST activity induced by MCT. MPO inhibitor 4-aminobenzoic acid hydrazide was found to reverse these alterations. Mpo-KO mice were resistant to the observed potentiating effect of inflammation on MCT-induced liver injury. In conclusion, inflammation intensified MCT-induced liver injury. MPO participated in the observed potentiating effect of inflammation on the hepatotoxicity induced by MCT.

Dapagliflozin reduces pulmonary vascular damage and susceptibility to atrial fibrillation in right heart disease

AIMS

Sodium-glucose cotransporter 2 inhibitors (SGLT2is) have made considerable progress in the field of heart failure, but their application in arrhythmia remains to be in-depth. Right heart disease (RHD) often leads to right heart dysfunction and is associated with atrial fibrillation (AF). Here, we explored the possible electrophysiologic effect of dapagliflozin (a type of SGLT2is) in the development of AF in rats with RHD.

METHODS AND RESULTS

Rats in the experimental group were intraperitoneally injected with a single dose of 60 mg/kg monocrotaline (MCT group, n = 32) on the first day of the experiment, whereas rats in the control group were injected with vehicle (CTL group, n = 32). Rats in the treatment subgroup were treated with dapagliflozin solution orally (MCT + DAPA and CTL + DAPA groups) for a total of 4 weeks, whereas rats in the rest of subgroups were given sterile drinking water. After 4 weeks, echocardiography demonstrated that MCT group rats developed obvious pulmonary arterial hypertension and right heart dysfunction. In addition, there were also obvious inflammatory infiltration, fibrosis, and muscularization in right atrial and pulmonary arteries. The P-wave duration (17.00 ± 0.53 ms, vs. 14.43 ± 0.57 ms in CTL; 14.00 ± 0.65 ms in CTL + DAPA; 14.57 ± 0.65 ms in MCT + DAPA; P < 0.05), RR interval (171.60 ± 1.48 ms, vs. 163.10 ± 1.10 ms in CTL; 163.30 ± 1.19 ms in CTL + DAPA; 163.10 ± 1.50 ms in MCT + DAPA; P < 0.05), Tpeak-Tend interval (65.93 ± 2.55 ms, vs. 49.55 ± 1.71 ms in CTL; 48.27 ± 3.08 ms in CTL + DAPA; P < 0.05), and corrected QT interval (200.90 ± 2.40 ms, vs. 160.00 ± 0.82 ms in CTL; 160.40 ± 1.36 ms in CTL + DAPA; 176.6 ± 1.57 ms in MCT + DAPA; P < 0.01) were significantly prolonged in the MCT group after 4 weeks, whereas P-wave amplitude (0.07 ± 0.0011 mV, vs. 0.14 ± 0.0009 mV in CTL; 0.14 ± 0.0011 mV in CTL + DAPA; 0.08 ± 0.0047 mV in MCT + DAPA; P < 0.05) and T-wave amplitude (0.04 ± 0.002 mV, vs. 0.13 ± 0.003 mV in CTL; 0.13 ± 0.003 mV in CTL + DAPA; P < 0.01) were decreased, and atrial 90% action potential duration (47.50 ± 0.93 ms, vs. 59.13 ± 2.1 ms in CTL; 59.75 ± 1.13 ms in CTL + DAPA; 60.63 ± 1.07 ms in MCT + DAPA; P < 0.01) and effective refractory periods (41.14 ± 0.88 ms, vs. 62.86 ± 0.99 ms in CTL; 63.14 ± 0.67 ms in CTL + DAPA; 54.86 ± 0.70 ms in MCT + DAPA; P < 0.01) were shortened. Importantly, the inducibility rate (80%, vs. 0% in CTL; 10% in CTL + DAPA; 40% in MCT + DAPA; P < 0.05) and duration of AF (30.85 ± 22.90 s, vs. 0 ± 0 s in CTL; 0.24 ± 0.76 s in CTL + DAPA; 5.08 ± 7.92 s in MCT + DAPA; P < 0.05) were significantly increased, whereas the expression levels of cardiac ion channels and calcium-handling proteins such as potassium/calcium channels and calmodulin were decreased. Mechanistically, 'NACHT, LRR, and PYD domain-containing protein 3' inflammasome-related pathway was significantly activated in the MCT group. Nevertheless, in the MCT + DAPA group, the above abnormalities were significantly improved.

CONCLUSIONS

Dapagliflozin reduces pulmonary vascular damage and right heart dysfunction, as well as the susceptibility to AF in RHD rats.

Protective and therapeutic effects of Scutellaria baicalensis and its main active ingredients baicalin and baicalein against natural toxicities and physical hazards: a review of mechanisms

OBJECTIVES

Scutellaria baicalensis (SB) has been traditionally used to combat a variety of conditions ranging from ischemic heart disease to cancer. The protective effects of SB are due to the action of two main flavonoids baicalin (BA) and baicalein (BE). This paper aimed to provide a narrative review of the protective and antidotal effects of SB and its main constituents against natural toxicities and physical hazards.

EVIDENCE ACQUISITION

Scientific databases Medline, Scopus, and Web of Science were thoroughly searched, based on different keywords for in vivo, in vitro and clinical studies which reported protective or therapeutic effects of SB or its constituents in natural and physical toxicities.

RESULTS

Numerous studies have reported that treatment with BE, BA, or total SB extract prevents or counteracts the detrimental toxic effects of various natural compounds and physical hazards. The toxic agents include mycotoxins, lipopolysaccharide, multiple plants and animal-derived substances as well as physical factors which negatively affected vital organs such as CNS, liver, kidneys, lung and heart. Increasing the expression of radical scavenging enzymes and glutathione content as well as inhibition of pro-inflammatory cytokines and pro-apoptotic mediators were important mechanisms of action.

CONCLUSION

Different studies on the Chinese skullcap have exhibited that its total root extract, BA or BE can act as potential antidotes or protective agents against the damage induced by natural toxins and physical factors by alleviating oxidative stress and inflammation. However, the scarcity of high-quality clinical evidence means that further clinical studies are required to reach a more definitive conclusion.

Protective effects of Dapagliflozin on the vulnerability of ventricular arrhythmia in rats with pulmonary artery hypertension induced by monocrotaline

Monocrotaline (MCT)-induced pulmonary artery hypertension (PAH) has been reported to cause right heart failure (RHF). Moreover, Right heart diseases have been determined to cause ventricular arrhythmia (VA). So we can conclude that MCT-induced PAH increases the incidence of VA. In addition, Previous studies have determined the benefits of Dapagliflozin (DA) on the cardiac system, but the responses of MCT-induced RHF to DA are not fully reported. So the present study sought to evaluate the effects of DA on the MCT-induced PAH. A dose intraperitoneal injection of MCT (60 mg/kg) was carried out to induce a rat model with PAH. DA (60 mg/l) was administered for 4 weeks following MCT injection. Echocardiography, body weight, blood pressure, blood glucose, electrophysiological study, and Western blot were performed. Four weeks after the MCT injection, MCT-treated rats decreased body weight, blood glucose and blood pressure. In addition, MCT caused the formation of PAH and RHF. Moreover, MCT-induced PAH rats increased the incidence of VA, prolonged action potential duration (APD), and shortened effective refractory period (ERP). Additionally, PAH rats significantly prevented the activated expressions of Ion channel proteins such as potassium channel (Kv1.5, Kv2.1, Kv4.2, Kv4.3) and L-type Ca channel (Cav1.2). As we expected, these changes above in PAH rats were reversed when DA was administered. Mechanistically, DA significantly reduced the levels of toll-like receptor (TLR4), the nuclear factor kappa B (NF-κB) in MCT-treated rats. In conclusion, these findings determine that DA reduces the vulnerability of VA in PAH rats through the TLR4/NF-κB signaling pathway.

Roles of Genetic Predisposition in the Sex Bias of Pulmonary Pathophysiology, as a Function of Estrogens : Sex Matters in the Prevalence of Lung Diseases

In addition to studies focused on estrogen mediation of sex-different regulation of systemic circulations, there is now increasing clinical relevance and research interests in the pulmonary circulation, in terms of sex differences in the morbidity and mortality of lung diseases such as inherent-, allergic- and inflammatory-based events. Thus, female predisposition to pulmonary artery hypertension (PAH) is an inevitable topic. To better understand the nature of sexual differentiation in the pulmonary circulation, and how heritable factors, in vivo- and/or in vitro-altered estrogen circumstances and changes in the live environment work in concert to discern the sex bias, this chapter reviews pulmonary events characterized by sex-different features, concomitant with exploration of how alterations of genetic expression and estrogen metabolisms trigger the female-predominant pathological signaling. We address the following: PAH (Sect.7.2) is characterized as an estrogenic promotion of its incidence (Sect. 7.2.2), as a function of specific germline mutations, and as an estrogen-elicited protection of its prognosis (Sect.7.2.1). More detail is provided to introduce a less recognized gene of Ephx2 that encodes soluble epoxide hydrolase (sEH) to degrade epoxyeicosatrienic acids (EETs). As a susceptible target of estrogen, Ephx2/sEH expression is downregulated by an estrogen-dependent epigenetic mechanism. Increases in pulmonary EETs then evoke a potentiation of PAH generation, but mitigation of its progression, a phenomenon similar to the estrogen-paradox regulation of PAH. Additionally, the female susceptibility to chronic obstructive pulmonary diseases (Sect. 7.3) and asthma (Sect.7.4), but less preference to COVID-19 (Sect. 7.5), and roles of estrogen in their pathogeneses are briefly discussed.

Blood microRNA Signatures Serve as Potential Diagnostic Biomarkers for Hepatic Sinusoidal Obstruction Syndrome Caused by Gynura japonica Containing Pyrrolizidine Alkaloids

Background and Aims: The Gynura japonica-induced hepatic sinusoidal obstruction syndrome (HSOS) is closely related to pyrrolizidine alkaloids (PAs), and its prevalence has been increasing worldwide in recent years. However, no effective therapy for PA-induced HSOS in clinics is available, partially due to the failure of quick diagnosis. This study aims to identify blood microRNA (miRNA) signatures as potential biomarkers for PA-induced HSOS in clinics.

Methods: The microarray-based miRNA profiling was performed on blood samples of the discovery cohort, which consisted of nine patients with HSOS and nine healthy donors. Differentially expressed miRNAs were further confirmed using a validation cohort, which consisted of 20 independent patients with HSOS. In addition, the rat model was established through the oral administration of the total alkaloid extract from G. japonica to investigate the association of miRNA biomarkers with the progression of HSOS. Bioinformatic analyses, including GO and KEGG enrichment, receiver operating characteristics curve, and correlation analyses were conducted to evaluate the accuracy of the potential miRNA biomarkers.

Results: Three miRNAs, namely miR-148a-3p, miR-362-5p, and miR-194-5p, were overexpressed in patients and rats with PA-induced HSOS. These miRNAs were positively related to the severity of liver injury and displayed considerable diagnostic accuracy for patients with HSOS with areas under the curve over 0.87.

Conclusion: In summary, this study demonstrated that three miRNAs, hsa-miR-148a-3p, hsa-miR-362-5p, and hsa-miR-194-5p, might serve as potential biomarkers for PA-induced HSOS in clinics.

Plexiform Lesions in an Experimental Model of Monocrotalin-Induced Pulmonary Arterial Hypertension

Fundamento

O modelo de hipertensão arterial pulmonar induzida por monocrotalina (MCT) é um dos mais reproduzidos atualmente, apresentando como limitação a ausência de lesões plexiformes, manifestações típicas da doença grave em humanos.

Objetivo

Avaliar a gravidade da arteriopatia pulmonar induzida por MCT por meio dos achados anatomopatológicos pulmonares e cardíacos, evolução clínica e sobrevida em 37 dias.

Métodos

Foram utilizados 50 ratos machos Wistar divididos em quatro grupos, sendo um controle (n = 10). Os três grupos restantes foram submetidos à inoculação de MCT (60 mg/kg i.p.) e ficaram sob o seu efeito por 15 (n = 10), 30 (n = 10) e 37 dias (n = 20). Ao final de cada período, os animais foram sacrificados, obtendo-se tecidos pulmonar e cardíaco para análise anatomopatológica e morfométrica. Empregou-se o teste Kruskal-Wallis, considerando nível de significância de 5%.

Resultados

Nos pulmões dos animais MCT foram constatadas lesões referentes à arteriopatia pulmonar, incluindo muscularização das arteríolas, hipertrofia da camada média e lesões neointimais concêntricas. Lesões complexas foram observadas nos grupos MCT, descritas como plexiforme e do “tipo” plexiforme (plexiform-like). A hipertrofia do ventrículo direito foi constatada pelo aumento da espessura e diâmetro dos cardiomiócitos e pelo aumento significativo da espessura da parede do ventrículo direito (p<0,0000).

Conclusão

O modelo foi capaz de gerar arteriopatia pulmonar moderada-grave associada à hipertrofia do ventrículo direito secundária, com sobrevida de 50% em 37 dias. De nosso conhecimento, este estudo foi o primeiro a constatar a presença de lesões vasculares complexas, semelhantes às observadas em pacientes com hipertensão arterial pulmonar grave, em modelo isolado de MCT. (Arq Bras Cardiol. 2020; 115(3):480-490)

Exercise preconditioning prevents left ventricular dysfunction and remodeling in monocrotaline-induced pulmonary hypertension

Background:

Despite pulmonary arterial hypertension (PAH) directly affects the right ventricle (RV), important structural, functional, and molecular changes also occur in left ventricle (LV). The objective of our study was to analyze the hypothetical cardioprotective effects of exercise preconditioning on LV in rats with monocrotaline (MCT)-induced PAH.

Methods:

Forty male Wistar rats were randomly separated in sedentary (SED) and trained group (EX; running sessions of 60 min/day, 5 days/wk, at 25 m/min, for 4 weeks). After 4 weeks, animals were injected with MCT (60 mg/kg; SED + MCT; EX + MCT) or vehicle (SED + V). Following an additional period of 4 weeks where all animals remained sedentary, we completed LV hemodynamic evaluation in baseline and isovolumic conditions and collected LV samples for histological and molecular analysis.

Results:

Preconditioning with exercise was capable to restore LV systolic and diastolic dysfunction in both baseline and isovolumic conditions (P < .05). This improved was paralleled with prevention of LV cardiomyocytes atrophy, fibrosis, and endothelin 1 mRNA levels (P < .05).

Conclusions:

Our findings suggest that exercise preconditioning can prevent LV dysfunction secondary to MCT-induced PAH, which is of particular interest for the familial form of the disease that is manifested by greater severity or earlier onset.

Monocrotaline-induced liver toxicity in rat predicted by a combined in vitro physiologically based kinetic modeling approach

The aim of the present study was to use an in vitro–in silico approach to predict the in vivo acute liver toxicity of monocrotaline and to characterize the influence of its metabolism on its relative toxic potency compared to lasiocarpine and riddelliine. In the absence of data on acute liver toxicity of monocrotaline upon oral exposure, the predicted dose–response curve for acute liver toxicity in rats and the resulting benchmark dose lower and upper confidence limits for 10% effect (BMDL₁₀ and BMDU₁₀) were compared to data obtained in studies with intraperitoneal or subcutaneous dosing regimens. This indicated the predicted BMDL₁₀ value to be in line with the no-observed-adverse-effect levels (NOAELs) derived from availabe in vivo studies. The predicted BMDL₁₀–BMDU₁₀ of 1.1–4.9 mg/kg bw/day also matched the oral dose range of 1–3 mg PA/kg bw/day at which adverse effects in human are reported. A comparison to the oral toxicity of the related pyrrolizidine alkaloids (PAs) lasiocarpine and riddelliine revealed that, although in the rat hepatocytes monocrotaline was less toxic than lasiocarpine and riddelliine, due to its relatively inefficient clearance, its in vivo acute liver toxicity was predicted to be comparable. It is concluded that the combined in vitro-PBK modeling approach can provide insight in monocrotaline-induced acute liver toxicity in rats, thereby filling existing gaps in the database on PA toxicity. Furthermore, the results reveal that the kinetic and metabolic properties of PAs can vary substantially and should be taken into account when considering differences in relative potency between different PAs.

Sugen-morphine model of pulmonary arterial hypertension

Pulmonary arterial hypertension is a fatal disease associated with pulmonary vascular remodeling and right ventricular hypertrophy. Pre-clinical animal models that reproduce the human pulmonary arterial hypertension process and pharmacological response to available therapies are critical for future drug development. The most prevalent animal model reproducing many aspects of angioobliterative forms of pulmonary arterial hypertension is the rat Sugen/hypoxia model in which Sugen, a vascular endothelial growth factor receptor antagonist, primarily causes initiation of endothelial injury and later in the presence of hypoxia promotes proliferation of apoptosis-resistant endothelial cells. We previously demonstrated that exposure of human pulmonary microvascular endothelium to morphine and HIV-proteins results in initial apoptosis followed by increased proliferation. Here, we demonstrate that the double-hit of morphine and Sugen 5416 (Sugen–morphine) in rats leads to the development of pulmonary arterial hypertension with significant medial hypertrophy of pre-acinar pulmonary arteries along with neo-intimal thickening of intra-acinar vessels. In addition, the pulmonary smooth muscle and endothelial cells isolated from Sugen–morphine rats showed hyperproliferation and apoptotic resistance, respectively, in response to serum starvation. Our findings support that the dual hit model of Sugen 5416 and morphine provides another experimental strategy to induce significant pulmonary vascular remodeling and development of severe pulmonary arterial hypertension pathology in rats without exposure to hypoxia.

Aquaporin-2 expression in the kidney and urine is elevated in rats with monocrotaline-induced pulmonary heart disease

Objective

Little is known about how renal aquaporin-2 (AQP2) expression is affected by right heart failure caused by pulmonary heart disease (PHD). Therefore, we examined the expression of AQP2 in a rat model of PHD induced by monocrotaline (MCT).

Methods

After 4 weeks of treatment, urine and blood samples were collected from sham-treated and MCT-treated rats. Plasma arginine vasopressin (AVP) levels were measured by radioimmunoassay, and kidney Aqp2 mRNA expression was detected by reverse transcription (RT)-PCR. Kidney AQP2 protein expression was quantified by immunohistochemistry and western blotting assays. The concentration of urine AQP2 was determined by indirect enzyme-linked immunosorbent assay.

Results

We successfully established an animal model of MCT-induced PHD in rats. MCT-treated rats had significantly higher mRNA and protein levels of AQP2 in their kidney tissue. Following MCT treatment, rats also had markedly increased concentrations of both urine AQP2 and plasma AVP.

Conclusions

AQP2 expression was significantly increased in the kidney tissues and urine of rats with PHD induced by MCT. Our findings suggest that the evaluation of AQP2 expression contributes to an early diagnosis of PHD, and may also be an important reference to improve PHD therapeutics.

β3 adrenergic receptor antagonist SR59230A exerts beneficial effects on right ventricular performance in monocrotaline-induced pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a high mortality rate. Previous studies have revealed the important function of the β3 adrenergic receptor (β3-AR) in cardiovascular diseases, and the potential beneficial effects of numerous β3-AR agonists on pulmonary vasodilation. Conversely, a number of studies have proposed that the antagonism of β3-AR may prevent heart failure. The present study aimed to investigate the functional involvement of β3-AR and the effects of the β3-AR antagonist, SR59230A, in PAH and subsequent heart failure. A rat PAH model was established by the subcutaneous injection of monocrotaline (MCT), and the rats were randomly assigned to groups receiving four weeks of SR59230A treatment or the vehicle control. SR59230A treatment significantly improved right ventricular function in PAH in vivo compared with the vehicle control (P<0.001). Additionally, the expression level of β3-AR was significantly upregulated in the lung and heart tissues of PAH rats compared with the sham group (P<0.01), and SR59230A treatment inhibited this increase in the lung (P<0.05), but not the heart. Specifically, SR59230A suppressed the elevated expression of endothelial nitric oxide and alleviated inflammatory infiltration to the lung under PAH conditions. These results are, to the best of our knowledge, the first to reveal that SR59230A exerts beneficial effects on right ventricular performance in rats with MCT-induced PAH. Furthermore, blocking β3-AR with SR59230A may alleviate the structural changes and inflammatory infiltration to the lung as a result of reduced oxidative stress.

Gynura Rhizoma containing pyrrolizidine alkaloids induces the hepatic sinusoidal obstruction syndrome in mice via upregulating fibrosis-related factors

Recently, hepatic sinusoidal obstruction syndrome (HSOS) caused by herbal preparations containing pyrrolizidine alkaloids (PAs), such as Gynura Rhizoma (Tusanqi), has gained global attention. However, the lack of a reliable and reproducible animal model has greatly hampered mechanistic studies. Therefore, we aimed to establish a reproducible HSOS mouse model and investigate the hepatotoxic mechanism. The model was established by intragastrical administration of Gynura Rhizoma extract, i.e., 1.0 g extract/kg per day (equal to 16.7 g crude drug/kg per day based on extraction rate and 49.1 mg PA/kg per day based on the total PA content in the extract determined) for 40 successive days. Then, the mice were sacrificed, and their blood samples and livers were collected for analyses. Using hematoxylin-eosin (HE) and Masson staining, scanning electron microscopy imaging, clinical biomarkers, and other assays, we showed that the HSOS was successfully induced in our mouse model. Furthermore, we detected the key factors involved in liver fibrosis in the mice, revealing significantly increased hydroxyproline concentration; elevated expression of α-smooth muscle actin (α-SMA) and fibrosis-related genes such as Collagen-1, Collagen-3, Mmp2, Mmp13, Timp1, Timp3, and Activin, upregulated Smad3 phosphorylation, and increased serum TGF-β levels. Moreover, pro-inflammatory cytokines, including Tnf-α, Il-1β, and Il-6, were also increased in the model. All these results demonstrate the key roles of the TGF-β-Smad3 and inflammatory signaling pathways in this Gynura Rhizoma-induced HSOS mouse model, suggesting that blockade of fibrosis and/or inflammation should be an effective treatment for HSOS.

Magnesium isoglycyrrhizinate has hepatoprotective effects in an oxaliplatin‑induced model of liver injury

Oxaliplatin is a core chemotherapeutic agent used for the treatment of colorectal liver metastasis; however, liver injury caused by oxaliplatin increases the risk of peri‑operative morbidity and mortality. Magnesium isoglycyrrhizinate (MgiG) is a magnesium salt of 18‑α glycyrrhizic acid stereoisomer that has demonstrated liver‑protective effects against toxins and hepatitis. In the present study, the liver‑protective effect of MgiG against oxaliplatin‑induced hepatic injury was examined in vitro and in vivo. The results demonstrated that MgiG had a protective effect against oxaliplatin‑induced liver injury, as evidenced by the alleviation of hepatic pathological damage and transaminase levels. The protective effect of MgiG was demonstrated to be correlated with inhibition of oxidative stress, the interleukin‑6 pathway and the coagulation system. Altogether, the present findings suggested that MgiG may have potential value in the clinical prevention and treatment of oxaliplatin‑induced liver injury.

Molecular pathogenesis and current pathology of pulmonary hypertension

Following its initial description over a century ago, pulmonary arterial hypertension (PAH) continues to challenge researchers committed to understanding its pathobiology and finding a cure. The last two decades have seen major developments in our understanding of the genetics and molecular basis of PAH that drive cells within the pulmonary vascular wall to produce obstructive vascular lesions; presently, the field of PAH research has taken numerous approaches to dissect the complex amalgam of genetic, molecular and inflammatory pathways that interact to initiate and drive disease progression. In this review, we discuss the current understanding of PAH pathology and the role that genetic factors and environmental influences share in the development of vascular lesions and abnormal cell function. We also discuss how animal models can assist in elucidating gene function and the study of novel therapeutics, while at the same time addressing the limitations of the most commonly used rodent models. Novel experimental approaches based on application of next generation sequencing, bioinformatics and epigenetics research are also discussed as these are now being actively used to facilitate the discovery of novel gene mutations and mechanisms that regulate gene expression in PAH. Finally, we touch on recent discoveries concerning the role of inflammation and immunity in PAH pathobiology and how they are being targeted with immunomodulatory agents. We conclude that the field of PAH research is actively expanding and the major challenge in the coming years is to develop a unified theory that incorporates genetic and mechanistic data to address viable areas for disease modifying drugs that can target key processes that regulate the evolution of vascular pathology of PAH.

Low dose monocrotaline causes a selective pulmonary vascular lesion in male and female pneumonectomized rats

Purpose/Aim: Low doses (30-80 mg/kg) of monocrotaline are commonly used to create experimental models of pulmonary hypertension in rats. At these doses, monocrotaline causes pulmonary endothelial apoptosis and acute lung injury which ultimately results in pulmonary vascular disease. Higher doses of monocrotaline (300 mg/kg) are known to create severe liver injury, but previous investigations with lower doses have not reported histology in other organs to determine whether the vascular injury with monocrotaline is pulmonary-selective or generalized.

MATERIALS AND METHODS

We therefore sought to determine whether monocrotaline caused extra-pulmonary injury at doses commonly used in pulmonary hypertension studies. We performed left pneumonectomy on young male and female rats before administering 50-60 mg/kg monocrotaline 7 days later. We monitored serum chemistry and urine dipsticks during the first 3 weeks while the animals developed pulmonary hypertension. After 3 weeks, we sacrificed animals and stained the lungs and highly vascular visceral organs (kidney, liver, and spleen) for elastin to evaluate the degree of vascular injury and remodeling.

RESULTS

We did not observe proteinuria or significant transaminitis over the 3 weeks following monocrotaline. As previously published, monocrotaline caused severe pulmonary vascular disease with neointimal lesions and medial hypertrophy. We did not identify significant large or small arterial damage in the kidneys, liver, or spleen. Two external veterinary pathologists did not identify histopathology in the kidneys, liver, or spleen of these rats.

CONCLUSIONS

We conclude that 50-60 mg/kg of monocrotaline causes a selective pulmonary vascular lesion and that male and female rats have little non-pulmonary damage over 3 weeks at these doses of monocrotaline.

Diethylcarbamazine: A potential treatment drug for pulmonary hypertension?

The present study demonstrated the potential effects of diethylcarbamazine (DEC) on monocrotaline (MCT)-induced pulmonary hypertension. MCT solution (600mg/kg) was administered once per week, and 50mg/kg body weight of DEC for 28days. Three C57Bl/6 male mice groups (n=10) were studied: Control; MCT_28, and MCT₂₈/DEC. Echocardiography analysis was performed and lung tissues were collected for light microscopy (hematoxylin-eosin and Masson's trichrome staining), immunohistochemistry (αSMA, FADD, caspase 8, caspase 3, BAX, BCL2, cytochrome C and caspase 9) western blot (FADD, caspase 8, caspase 3, BAX, BCL2, cytochrome C and caspase 9) and qRt-PCR (COL-1α and αSMA). Echocardiography analysis demonstrated an increase in the pulmonary arterial blood flow gradient and velocity in the systole and RV area in the MCT28 group, while treatment with DEC resulted in a significant reduction in these parameters. Deposition of collagen fibers and αSMA staining around the pulmonary arteries was evident in the MCT28 group, while treatment with DEC reduced both. Western blot analysis revealed a decrease in BMPR2 in the MCT28 group, in contrast DEC treatment resulted in a significant increase in the level of BMPR2. DEC also significantly reduced the level of VEGF compared to the MCT28 group. Apoptosis extrinsic and intrinsic pathway markers were reduced in the MCT28 group. After treatment with DEC these levels returned to baseline. The results of this study indicate that DEC attenuates PH in an experimental monocrotaline-induced model by inhibiting a series of markers involved in cell proliferation/death.

Bucindolol improves right ventricle function in rats with pulmonary arterial hypertension through the reversal of autonomic imbalance

Pulmonary arterial hypertension (PAH) is characterised by an elevation in afterload imposed on the right ventricle (RV), leading to hypertrophy and failure. The autonomic nervous system (ANS) plays a key role in the progression to heart failure, and the use of beta-blockers attenuates this process. The aim of this study was to verify the role of bucindolol, aβ1-, β2- and α1-blocker, on the ANS, and its association with RV function in rats with PAH. Male Wistar rats were divided into four groups: control, monocrotaline, control+bucindolol, and monocrotaline+bucindolol. PAH was induced by a single intraperitoneal injection of monocrotaline (60mg/kg). After two weeks, animals were treated for seven days with bucindolol (2mg/kg/day i.p.) or vehicle. At the end of the treatment, animals underwent echocardiographic assessment, catheterisation of the femoral artery and RV, and tissue collection for morphometric and histological evaluation. In the monocrotaline+bucindolol group, there was a decrease in mean pulmonary artery pressure (33%) and pulmonary congestion (21%), when compared to the monocrotaline. Bucindolol treatment also reduced RV pleomorphism, necrosis, fibrosis and infiltration of inflammatory cells. An improvement in RV systolic function was also observed in the monocrotaline+bucindolol group compared to the monocrotaline. In addition, bucindolol promoted a decrease in the cardiac sympathovagal balance (93%) by reducing sympathetic drive (70%) and increasing parasympathetic drive (142%). Bucindolol also reduced blood pressure variability (75%). Our results show that the beneficial effects from bucindolol treatment appeared to be a consequence of the reversal of monocrotaline-induced autonomic imbalance.

Animal models of cardiac cachexia

Cachexia is the loss of body weight associated with several chronic diseases including chronic heart failure (CHF). The cachectic condition is mainly due to loss of skeletal muscle mass and adipose tissue depletion. The majority of experimental in vivo studies on cachexia rely on animal models of cancer cachexia while a reliable and appropriate model for cardiac cachexia has not yet been established. A critical issue in generating a cardiac cachexia model is that genetic modifications or pharmacological treatments impairing the heart functionality and used to obtain the heart failure model might likely impair the skeletal muscle, this also being a striated muscle and sharing with the myocardium several molecular and physiological mechanisms. On the other hand, often, the induction of heart damage in the several existing models of heart failure does not necessarily lead to skeletal muscle loss and cachexia. Here we describe the main features of cardiac cachexia and illustrate some animal models proposed for cardiac cachexia studies; they include the genetic calsequestrin and Dahl salt-sensitive models, the monocrotaline model and the surgical models obtained by left anterior descending (LAD) ligation, transverse aortic constriction (TAC) and ascending aortic banding. The availability of a specific animal model for cardiac cachexia is a crucial issue since, besides the common aspects of cachexia in the different syndromes, each disease has some peculiarities in its etiology and pathophysiology leading to cachexia. Such peculiarities need to be unraveled in order to find new targets for effective therapies.

Metabolic Changes Precede the Development of Pulmonary Hypertension in the Monocrotaline Exposed Rat Lung

There is increasing interest in the potential for metabolic profiling to evaluate the progression of pulmonary hypertension (PH). However, a detailed analysis of the metabolic changes in lungs at the early stage of PH, characterized by increased pulmonary artery pressure but prior to the development of right ventricle hypertrophy and failure, is lacking in a preclinical animal model of PH. Thus, we undertook a study using rats 14 days after exposure to monocrotaline (MCT), to determine whether we could identify early stage metabolic changes prior to the manifestation of developed PH. We observed changes in multiple pathways associated with the development of PH, including activated glycolysis, increased markers of proliferation, disruptions in carnitine homeostasis, increased inflammatory and fibrosis biomarkers, and a reduction in glutathione biosynthesis. Further, our global metabolic profile data compare favorably with prior work carried out in humans with PH. We conclude that despite the MCT-model not recapitulating all the structural changes associated with humans with advanced PH, including endothelial cell proliferation and the formation of plexiform lesions, it is very similar at a metabolic level. Thus, we suggest that despite its limitations it can still serve as a useful preclinical model for the study of PH.

Fast and reliable detection of toxic Crotalaria spectabilis Roth. in Thunbergia laurifolia Lindl. herbal products using DNA barcoding coupled with HRM analysis

Background

Nowadays, medicinal plants are used as a popular alternative to synthetic drugs. Many medicinal plant products have now been commercialized throughout various markets. These products are commonly sold in processed or modified forms such as powders, dried material and capsules, making it almost impossible to accurately identify the constituent species. The herbal plant known as ‘Rang Chuet’ in Thai has been widely used as remedies for various ailments. However, two medicinal plants species, Thunbergia laurifolia and Crotalaria spectabilis share this name. Duo to the similarity in nomenclature, the commercial products labeled as ‘Rang Chuet’ could be any of them. Recently, the evidence of hepatotoxic effects linked to use of C. spectabilis were reported and is now seriously concern. There is a need to find an approach that could help with species identification of these herbal products to ensure the safety and efficacy of the herbal drug.

Methods

Here DNA barcoding was used in combination with High Resolution Melting analysis (Bar-HRM) to authenticate T. laurifolia species. Four DNA barcodes including matK, rbcL, rpoC and trnL were selected for use in primers design for HRM analysis to produce standard melting profiles of the selected species. Commercial products labeled as ‘Rang Chuet’ were purchased from Thai markets and authentication by HRM analyses.

Results

Melting data from the HRM assay using the designed primers showed that the two ‘Rang Chuet’ species could easily be distinguished from each other. The melting profiles of the all four region amplicons of each species are clearly separated in all three replicates. The method was then applied to authenticate products in powdered form. HRM curves of all ten test samples indicated that three of the tested products did not only contain the T. laurifolia species.

Conclusion

The herbal drugs derived from different plants must be distinguished from each other even they share the same vernacular name. The Bar-HRM method developed here proved useful in the identification and authentication of herbal species in processed samples. In the future, species authentication through Bar-HRM could be used to promote consumer trust, as well as raising the quality of herbal products.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-015-0692-6) contains supplementary material, which is available to authorized users.

The effects of gender difference on monocrotaline-induced pulmonary hypertension in rats

The present study aimed to compare the effect of gender difference on hemodynamic consequences in the development of monocrotaline (MCT)-induced pulmonary hypertension in rat. The effect of antioxidant enzyme systems on the development of pulmonary hypertension mediated by the phytotoxin MCT and the effect of gender on these antioxidant systems were also investigated. For this purpose, the right ventricular pressures (RVPs) and right ventricular/heart weight (HW) ratios were compared between groups and the glutathione (GSH) level and superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) activities were determined in lung and liver tissue samples of rats. RVP and right ventricular/HW ratios significantly increased in the MCT group compared to the control group. In the MCT group, RVP was significantly higher in males than females. MCT-induced pulmonary hypertension resulted in decreased GSH level, decreased GST and SOD activities and increased CAT activity in lung and liver tissues of both male and female rats. In addition, the lung and liver GSH level and GST and SOD levels were higher in female control rats compared to male control rats. The results of the present study, that antioxidant enzyme activities were different between the groups, highlight the possible role of oxidative stress in the pathogenesis of MCT-induced pulmonary hypertension in rats. Moreover, the lower antioxidant defense capacity of male rats than female rats may be considered as a cause of more aggressive course of MCT-induced pulmonary hypertension in males compared to females.

Pathogenesis of FOLFOX induced sinusoidal obstruction syndrome in a murine chemotherapy model

BACKGROUND & AIMS

Sinusoidal obstruction syndrome (SOS) following oxaliplatin based chemotherapy can have a significant impact on post-operative outcome following resection of colorectal liver metastases. To date no relevant experimental models of oxaliplatin induced SOS have been described. The aim of this project was to establish a rodent model which could be utilised to investigate mechanisms underlying SOS to aid the development of therapeutic strategies.

METHODS

C57Bl/6 mice, maintained on a purified diet, were treated with intra-peritoneal FOLFOX (n=10), or vehicle (n=10), weekly for five weeks and culled one week following final treatment. Sections of the liver and spleen were fixed in formalin and paraffin embedded for histological analysis. The role of oxidative stress on experimental-induced SOS was determined by dietary supplementation with butylated hydroxyanisole and N-acetylcysteine.

RESULTS

FOLFOX treatment was associated with the development of sinusoidal dilatation and hepatocyte atrophy on H&E stained sections of the liver in keeping with SOS. Immunohistochemistry for p21 demonstrated the presence of replicative senescence within the sinusoidal endothelium. FOLFOX induced endothelial damage leads to a pro-thrombotic state within the liver associated with upregulation of PAI-1 (p<0.001), vWF (p<0.01) and Factor X (p<0.001), which may contribute to the propagation of liver injury. Dietary supplementation with the antioxidant BHA prevented the development of significant SOS.

CONCLUSIONS

We have developed the first reproducible model of chemotherapy induced SOS that reflects the pathogenesis of this disease in patients. It appears that the use of antioxidants alongside oxaliplatin based chemotherapy may be of value in preventing the development of SOS in patients with colorectal liver metastases.

Therapeutic efficacy of AAV1.SERCA2a in monocrotaline-induced pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is characterized by dysregulated proliferation of pulmonary artery smooth muscle cells leading to (mal)adaptive vascular remodeling. In the systemic circulation, vascular injury is associated with downregulation of sarcoplasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) and alterations in Ca(2+) homeostasis in vascular smooth muscle cells that stimulate proliferation. We, therefore, hypothesized that downregulation of SERCA2a is permissive for pulmonary vascular remodeling and the development of PAH.

METHODS AND RESULTS

SERCA2a expression was decreased significantly in remodeled pulmonary arteries from patients with PAH and the rat monocrotaline model of PAH in comparison with controls. In human pulmonary artery smooth muscle cells in vitro, SERCA2a overexpression by gene transfer decreased proliferation and migration significantly by inhibiting NFAT/STAT3. Overexpresion of SERCA2a in human pulmonary artery endothelial cells in vitro increased endothelial nitric oxide synthase expression and activation. In monocrotaline rats with established PAH, gene transfer of SERCA2a via intratracheal delivery of aerosolized adeno-associated virus serotype 1 (AAV1) carrying the human SERCA2a gene (AAV1.SERCA2a) decreased pulmonary artery pressure, vascular remodeling, right ventricular hypertrophy, and fibrosis in comparison with monocrotaline-PAH rats treated with a control AAV1 carrying β-galactosidase or saline. In a prevention protocol, aerosolized AAV1.SERCA2a delivered at the time of monocrotaline administration limited adverse hemodynamic profiles and indices of pulmonary and cardiac remodeling in comparison with rats administered AAV1 carrying β-galactosidase or saline.

CONCLUSIONS

Downregulation of SERCA2a plays a critical role in modulating the vascular and right ventricular pathophenotype associated with PAH. Selective pulmonary SERCA2a gene transfer may offer benefit as a therapeutic intervention in PAH.

Thrombin has biphasic effects on the nitric oxide-cGMP pathway in endothelial cells and contributes to experimental pulmonary hypertension

Background

A potential role for coagulation factors in pulmonary arterial hypertension has been recently described, but the mechanism of action is currently not known. Here, we investigated the interactions between thrombin and the nitric oxide-cGMP pathway in pulmonary endothelial cells and experimental pulmonary hypertension.

Principal Findings

Chronic treatment with the selective thrombin inhibitor melagatran (0.9 mg/kg daily via implanted minipumps) reduced right ventricular hypertrophy in the rat monocrotaline model of experimental pulmonary hypertension. In vitro, thrombin was found to have biphasic effects on key regulators of the nitric oxide-cGMP pathway in endothelial cells (HUVECs). Acute thrombin stimulation led to increased expression of the cGMP-elevating factors endothelial nitric oxide synthase (eNOS) and soluble guanylate cyclase (sGC) subunits, leading to increased cGMP levels. By contrast, prolonged exposition of pulmonary endothelial cells to thrombin revealed a characteristic pattern of differential expression of the key regulators of the nitric oxide-cGMP pathway, in which specifically the factors contributing to cGMP elevation (eNOS and sGC) were reduced and the cGMP-hydrolyzing PDE5 was elevated (qPCR and Western blot). In line with the differential expression of key regulators of the nitric oxide-cGMP pathway, a reduction of cGMP by prolonged thrombin stimulation was found. The effects of prolonged thrombin exposure were confirmed in endothelial cells of pulmonary origin (HPAECs and HPMECs). Similar effects could be induced by activation of protease-activated receptor-1 (PAR-1).

Conclusion

These findings suggest a link between thrombin generation and cGMP depletion in lung endothelial cells through negative regulation of the nitric oxide-cGMP pathway, possibly mediated via PAR-1, which could be of relevance in pulmonary arterial hypertension.

Cross talk between autophagy and apoptosis in pulmonary hypertension

Endothelial cell (EC) apoptosis and apoptosis resistant proliferation have been proposed to play crucial roles in the development of featured plexiform lesions in the pathogenesis of pulmonary hypertension (PH). Subsequently, EC injury associated smooth muscle cell (SMC) proliferation facilitates vascular remodeling and eventually leads to narrowed vascular lumen, increased pulmonary vascular resistance, increased pulmonary arterial pressure, and right heart failure. The imbalance between cell death and proliferation occurs in every stage of pulmonary vascular remodeling and pathogenesis of PH, and involves every cell type in the vasculature including, but not limited to ECs, SMCs, and fibroblasts. Despite extensive studies, the detailed cellular and molecular mechanisms on how the transition from initial apoptosis of ECs to apoptosis resistant proliferation on ECs and SMCs remains unclear. Recent knowledge on autophagy, a conservative and powerful regulatory machinery existing in almost all mammalian cells, has shed light on the complex and delicate control on cell fate in the development of vascular remodeling in PH. In this review, we will discuss the recent understandings on how the cross-talk between apoptosis and autophagy regulates cell death or proliferation in PH pathogenesis, particularly in pulmonary vascular remodeling involving ECs and SMCs.

Assessment of the endothelial functions in monocrotaline-induced pulmonary hypertension

Pulmonary hypertension (PH) is a life-threatening disease that causes endothelial dysfunction in the pulmonary vascular bed. Systemic endothelial dysfunction has also been reported in PH. This study compared the systemic and pulmonary vascular responses and some blood biomarkers of endothelial function in monocrotaline (MCT)-induced PH of rats. It also investigated the effect of sildenafil and iloprost treatment. MCT application induced elevation in the right ventricular pressures of the rat heart that had been reversed by sildenafil and iloprost treatment. Acetylcholine-induced endothelium-dependent relaxations of the isolated pulmonary artery were decreased in the PH group and this failure was reversed by sildenafil and iloprost treatment. Acetylcholine-induced endothelium-dependent relaxations of the isolated thoracic aorta were similar in all groups. Serotonin-induced contractions of the pulmonary artery were augmented by PH. In the isolated aorta, serotonin-stimulated contraction was not different in the control and MCT groups, but sildenafil and iloprost treatment decreased serotonin responses. The nitric oxide (NO) level in systemic circulation was not significantly changed by PH. However, sildenafil and iloprost treatments caused a decrease in the plasma level of NO. Asymmetric dimethylarginine levels in plasma were significantly decreased after MCT application and were not recovered by sildenafil and iloprost treatment. Total antioxidant capacity and H2S level of plasma were similar in all groups. Results of this study showed that MCT-induced PH caused specific toxic effects on pulmonary vasculature without any functional effects on the aorta. In addition, it was also demonstrated that sildenafil and iloprost treatments were effective in the MCT-induced PH.

Croix CM, Watkins SC, Fleming AM, Champion HC, Mason RP, Freeman BA, Kelley EE. Obesity-induced tissue free radical generation: an in vivo immuno-spin trapping study

Assessment of tissue free radical production is routinely accomplished by measuring secondary by-products of redox reactions and/or diminution of key antioxidants such as reduced thiols. However, immuno-spin trapping, a newly developed immunohistochemical technique for detection of free radical formation, is garnering considerable interest as it allows for the visualization of 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-adducted molecules. Yet, to date, immuno-spin trapping reports have utilized in vivo models in which successful detection of free radical adducts required exposure to lethal levels of oxidative stress not reflective of chronic inflammatory disease. To study the extents and anatomic locations of more clinically relevant levels of radical formation, we examined tissues from high-fat (HF) diet-fed mice, a model of low-grade chronic inflammation known to demonstrate enhanced rates of reactive species production. Mice subjected to 20 weeks of HF diet displayed increased free radical formation (anti-DMPO mean fluorescence staining) in skeletal muscle (0.863±0.06 units vs 0.512±0.07 units), kidney (0.076±0.0036 vs 0.043±0.0025), and liver (0.275±0.012 vs 0.135±0.014) compared to control mice fed normal laboratory chow (NC). Western blot analysis of tissue homogenates confirmed these results showing enhanced DMPO immunoreactivity in HF mice compared to NC samples. The obesity-related results were confirmed in a rat model of pulmonary hypertension and right heart failure in which intense immunodetectable radical formation was observed in the lung and right ventricle of monocrotaline-treated rats compared to saline-treated controls. Combined, these data affirm the utility of immuno-spin trapping as a tool for in vivo assessment of altered extents of macromolecule oxidation to radical intermediates under chronic inflammatory conditions.

Cardiac-specific genetic inhibition of nuclear factor-κB prevents right ventricular hypertrophy induced by monocrotaline

Uncontrolled pulmonary arterial hypertension (PAH) results in right ventricular (RV) hypertrophy (RVH), progressive RV failure, and low cardiac output leading to increased morbidity and mortality (McLaughlin VV, Archer SL, Badesch DB, Barst RJ, Farber HW, Lindner JR, Mathier MA, McGoon MD, Park MH, Rosenson RS, Rubin LJ, Tapson VF, Varga J. J Am Coll Cardiol 53: 1573–1619, 2009). Although the exact figures of its prevalence are difficult to obtain because of the diversity of identifiable causes, it is estimated that the incidence of pulmonary hypertension is seven to nine cases per million persons in the general population and is most prevalent in the age group of 20–40, occurring more commonly in women than in men (ratio: 1.7 to 1; Rubin LJ. N Engl J Med 336: 111–117, 1997). PAH is characterized by dyspnea, chest pain, and syncope. Unfortunately, there is no cure for this disease and medical regimens are limited (Simon MA. Curr Opin Crit Care 16: 237–243, 2010). PAH leads to adverse remodeling that results in RVH, progressive right heart failure, low cardiac output, and ultimately death if left untreated (Humbert M, Morrell NW, Archer SL, Stenmark KR, MacLean MR, Lang IM, Christman BW, Weir EK, Eickelberg O, Voelkel NF, Rabinovitch M. J Am Coll Cardiol 43: 13S-24S, 2004; Humbert M, Sitbon O, Simonneau G. N Engl J Med 351: 1425–1436, 2004. LaRaia AV, Waxman AB. South Med J 100: 393–399, 2007). As there are no direct tools to assess the onset and progression of PAH and RVH, the disease is often detected in later stages marked by full-blown RVH, with the outcome predominantly determined by the level of increased afterload (D'Alonzo GE, Barst RJ, Ayres SM, Bergofsky EH, Brundage BH, Detre KM, Fishman AP, Goldring RM, Groves BM, Kernis JT, et al. Ann Intern Med 115: 343–349, 1991; Sandoval J, Bauerle O, Palomar A, Gomez A, Martinez-Guerra ML, Beltran M, Guerrero ML. Validation of a prognostic equation Circulation 89: 1733–1744, 1994). Various studies have been performed to assess the genetic, biochemical, and morphological components that contribute to PAH. Despite major advances in the understanding of the pathogenesis of PAH, the molecular mechanism(s) by which PAH promotes RVH and cardiac failure still remains elusive. Of all the mechanisms involved in the pathogenesis, inflammation and oxidative stress remain the core of the etiology of PAH that leads to development of RVH (Dorfmüller P, Perros F, Balabanian K, Humbert M. Eur Respir J 22: 358–363, 2003).

Cytotoxicity of monocrotaline in isolated rat hepatocytes: effects of dithiothreitol and fructose

Monocrotaline (MCT) is a pyrrolizidine alkaloid present in plants of the Crotalaria species that causes cytotoxicity and genotoxicity, including hepatotoxicity in animals and humans. It is metabolized by cytochrome P-450 in the liver to the alkylating agent dehydromonocrotaline (DHM). In previous studies using isolated rat liver mitochondria, we observed that DHM, but not MCT, inhibited the activity of respiratory chain complex I and stimulated the mitochondrial permeability transition with the consequent release of cytochrome c. In this study, we evaluated the effects of MCT and DHM on isolated rat hepatocytes. DHM, but not MCT, caused inhibition of the NADH-linked mitochondrial respiration. When hepatocytes of rats pre-treated with dexamethasone were incubated with MCT (5 mM), they showed ALT leakage, impaired ATP production and decreased levels of intracellular reduced glutathione and protein thiols. In addition, MCT caused cellular death by apoptosis. The addition of fructose or dithiotreitol to the isolated rat hepatocyte suspension containing MCT prevented the ATP depletion and/or glutathione or thiol oxidation and decreased the ALT leakage and apoptosis. These results suggest that the toxic effect of MCT on hepatocytes may be caused by metabolite-induced mitochondrial energetic impairment, together with a decrease of cellular glutathione and protein thiols.

What has been learnt from the thrombin-activatable fibrinolysis inhibitor-deficient mouse?

SUMMARY

Thrombin-activatable fibrinolysis inhibitor (TAFI) is a circulating zymogen that is activated physiologically by the thrombin/thrombomodulin complex to activated TAFI (TAFIa) which is a basic carboxypeptidase. Substrates include fibrin, leading to a reduction in rate of plasmin generation, and several proinflammatory mediators such as bradykinin, thrombin-cleaved osteopontin and complement factor C5a. TAFI-deficient mice have no phenotype without being challenged and TAFIa appears to play a limited role in physiological fibrinolysis in vivo. In several disease models, the TAFI-deficient mice have different outcomes from the wild type (WT), but whether the difference is beneficial or an exacerbation of the disease depends on the model. The consequences of TAFI deficiency include increased plasmin as a result of enhanced incorporation of plasminogen and tissue plasminogen activator into the fibrin clot, but also loss of its ability to degrade other substrates, with the resultant up-regulation of several proinflammatory mediators, including C5a. Criteria are recommended to demonstrate that a substrate is a physiological substrate of TAFIa.

Possible involvement of mitochondrial energy-producing ability in the development of right ventricular failure in monocrotaline-induced pulmonary hypertensive rats

The present study was undertaken to explore the possible involvement of alterations in the mitochondrial energy-producing ability in the development of the right ventricular failure in monocrotaline-administered rats. The rats at the 6th week after subcutaneous injection of 60 mg/kg monocrotaline revealed marked myocardial hypertrophy and fibrosis, that is, severe cardiac remodeling. The time-course study on the cardiac hemodynamics of the monocrotaline-administered rat by the cannula and echocardiographic methods showed a reduction in cardiac double product, a decrease in cardiac output index, and an increase in the right ventricular Tei index, suggesting that the right ventricular failure was induced at the 6th week after monocrotaline administration in rats. The mitochondrial oxygen consumption rate of the right ventricular muscle isolated from the monocrotaline-administered animal was decreased, which was associated with a reduction in myocardial high-energy phosphates. Furthermore, the decrease in mitochondrial oxygen consumption rate was inversely related to the increase in the right ventricular Tei index of the monocrotaline-administered rats. These results suggest that impairment of the mitochondrial energy-producing ability is involved in the development of the right ventricular failure in monocrotaline-induced pulmonary hypertensive rats.

Engraftment of syngeneic and allogeneic endothelial cells, hepatocytes and cholangiocytes into partially hepatectomized rats previously treated with mitomycin C

BACKGROUND

Pretreatment with retrorsine crosslinks host hepatocyte DNA and prevents proliferation after partial hepatectomy (PH), allowing selective expansion of transplanted progenitors. Shortcomings are length of protocol and carcinogenicity of retrorsine.

METHODS

This report describes a rapid liver repopulation protocol using mitomycin C (MMC) to block proliferation of rat hepatocytes in response to PH. One week post-MMC treatment, dipeptidyl peptidase IV negative host rats were given a PH followed by injection of late gestation, newborn, or adult total liver isolates from dipeptidyl peptidase IV positive rats. For allogeneic transplantation, host rats received injections of anti-CD3 antibody before and after PH.

RESULTS

Host liver staining 2 to 9 weeks posttransplantation revealed well-defined donor hepatocyte colonies with strong canalicular dipeptidyl peptidase IV activity. At the same cell dose, fetal and newborn isolates produced more colonies than adult liver isolates. Hepatocyte colonies also coexpressed marker proteins characteristic of adult hepatocytes and showed polarized localization of plasma membrane proteins. Host livers contained large clusters of sinusoids lined by dipeptidyl peptidase IV positive endothelial cells coexpressing the endothelial cell marker, RECA-1, but lacked the canalicular marker leucine aminopeptidase. Colonies containing donor hepatocytes, endothelial cells, and bile ducts were also observed. Similar levels of engraftment and expansion were achieved with allogeneic liver cell isolates by using anti-CD3 antibody treatment.

CONCLUSIONS

The MMC transplantation model provides a rapid method for engraftment and expansion of hepatocytes, endothelial cells, and cholangiocytes and should be applicable to investigations centering on the role of endothelial cells in liver regeneration and the identification and characterization of putative endothelial, hepatocyte, and cholangiocyte progenitors.

Alterations in pharmacological action of the right ventricle of monocrotaline-induced pulmonary hypertensive rats

The present study was undertaken to elucidate pathophysiological and pharmacological alterations in the right ventricle in monocrotaline-administered (MCT) rats. Examination of tissue weights of the MCT and age-matched control (CON) rats indicated the right ventricular (RV) hypertrophy until 8 weeks after a single subcutaneous administration of 60 mg/kg MCT. Apparent fibrosis in the right ventricle of the MCT rat at the 6th week (6w-MCT) was observed. Echocardiographic measurement of the cardiac and hemodynamic parameters of the MCT rat showed decreases in cardiac output and stroke volume indices at the 6th and 8th weeks. The RV Tei index, which increase represents aggravation of RV function, was augmented at the 4th to 8th week. The results suggest the genesis of cardiac and RV failure until 6 weeks after MCT administration. Injection of dobutamine (300 ng) or colforsin daropate (1 microg) into the perfused right ventricle isolated from CON rat at the 6th week resulted in a marked increase in cardiac double product, whereas injection of either agent into the right ventricle from the 6w-MCT rat elicited a small increase in the double product, followed by a sustained decrease in the developed tension. Infusion of acetylcholine (1 microg) into the RV muscle of the 6w-MCT rat resulted in prolongation of the periods for cardiac arrest and for bradycardia of the right ventricle. The results suggest that MCT administration causes the RV hypertrophy and eventually leads to the RV failure, accompanied by abnormal inotropic and chronotropic actions of the RV muscle.

Protective effects of hydroalcoholic extract from rhizomes of Cynodon dactylon (L.) Pers. on compensated right heart failure in rats

Background

The rhizomes of Cynodon dactylon are used for the treatment of heart failure in folk medicine. In the present study, we investigated the effects of hydroalcoholic extract of C. dactylon rhizomes on cardiac contractility in normal hearts and on cardiac functions in right-heart failure in rats.

Methods

Right-heart failure was induced by intraperitoneal injection of monocrotaline (50 mg/kg). Two weeks later, the animals were treated orally with different doses of the extract for fifteen days. At the end of the experiments cardiac functions and markers of myocardial hypertrophy were measured.

Results

The treated rats showed very less signs of fatigue, peripheral cyanosis and dyspnea. The survival rate was high in the extract treated groups (90%). Administration of C. dactylon in monocrotaline-injected rats led to profound improvement in cardiac functions as demonstrated by decreased right ventricular end diastolic pressure (RVEDP) and elevated mean arterial pressure. RVdP/dt_max, and RVdP/dt/P as indices of myocardial contractility were also markedly (p < 0.001; using one way ANOVA) increased by the extract. The extract reduced heart and lung congestion by decreasing tissue wet/dry and wet/body weight ratios (p < 0.01). In the isolated rat hearts, the extract produced a remarkable (P < 0.001) positive inotropic effect concomitant with a parallel decrease in LVEDP.

Conclusion

The results of this study indicated that C. dactylon exerted a strong protective effect on right heart failure, in part by positive inotropic action and improving cardiac functions.

Endothelin receptor antagonists in preclinical models of pulmonary hypertension

Pulmonary hypertension (PH), a chronic disorder of the pulmonary vasculature, is characterized by progressive elevation in pulmonary artery pressure and the ultimate development of right-sided heart failure and death. Being a rapidly progressive disease with limited therapeutic options, the pathogenesis of PH is complex and multifactorial. The pathogenesis may result from a combination of vasoconstriction, inward vascular wall remodelling and in situ thrombosis that involves dysfunction of underlying cellular pathways and mediators. Among these, the activation of endothelin (ET) system has been shown to be important in the development and perpetuation of PH. Endothelin-1 (ET-1), a potent vasoconstrictor and mitogen, exerts its biological effects by binding to two G-protein-coupled receptor isoforms, endothelin A (ETA) receptor and endothelin B (ETB) receptor. These two receptors are nonredundant and unique because of distinct localization, unique binding locations and affinities for the endothelin peptide and activation of distinct signalling pathways. Importantly, there is now substantial evidence that direct antagonism of ET receptors that can block either ETA- or ETA- and ETB receptors can be beneficial for the treatment of PH in both preclinical and clinical setting. This review provides an overview of endothelin biology, various preclinical models that have been widely used to investigate the pathophysiology of PH as well as the individual roles of the ET receptors (ETA and ETB) and their regulation in disease pathogenesis. We also review current data on the use of selective and nonselective ET receptor antagonism in the preclinical PH models.

Inhibition of the soluble epoxide hydrolase attenuates monocrotaline-induced pulmonary hypertension in rats

OBJECTIVES

The soluble epoxide hydrolase (sEH) metabolizes epoxyeicosatrienoic acids (EETs) to their less active dihydroxy derivatives. Because EETs have antiinflammatory properties, we determined whether or not inhibition of sEH attenuates disease development in the monocrotaline model of pulmonary hypertension in rats.

METHODS

sEH inhibition was achieved using 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (25 mg/l) and cis- 4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (5 mg/l) administered via drinking water starting 3 days prior to monocrotaline injection (60 mg/kg).

RESULTS

Monocrotaline induced the development of progressive pulmonary hypertension. sEH inhibition increased the plasma ratio of EETs to DHETs and attenuated the monocrotaline-induced increase in pulmonary artery medial wall thickness as well as the degree of vascular muscularization. Moreover, right ventricular pressure was significantly lower in the group treated with sEH inhibitors. Pulmonary sEH protein expression and sEH activity, as well as pulmonary cytochrome P450 epoxygenase activity were all impaired in monocrotaline-treated rats as compared with control animals. sEH inhibitors, however, increased the plasma ratio of EETs to dihydroxy epoxyeicosatrienoic acids. Monocrotaline induced the proliferation of pulmonary endothelial and vascular smooth muscle cells in vivo as determined by 5-Bromo-2'-deoxy-Uridine incorporation, and this effect was significantly blunted in animals treated with sEH inhibitors. Proliferation of cultured pulmonary smooth muscle cell, however, was not affected by EETs or sEH inhibitors suggesting that the in-vivo effects are a consequence of a direct EET-mediated protection against the inflammation induced by monocrotaline.

CONCLUSION

sEH inhibition reduces pulmonary vascular remodeling and the development of pulmonary hypertension in the monocrotaline model of primary pulmonary hypertension in rats.

Dehydromonocrotaline induces cyclosporine A-insensitive mitochondrial permeability transition/cytochrome c release

Monocrotaline (MCT) is a pyrrolizidine alkaloid present in plants of the genus Crotalaria that causes cytotoxicity and genotoxicity in animals and humans. It is well established that the toxicity of MCT results from its hepatic bioactivation to dehydromonocrotaline (DHM), an alkylating agent, but the exact mechanism of action remains unknown. In a previous study, we demonstrated DHM's inhibition of mitochondrial NADH-dehydrogenase activity at micromolar concentrations, which is an effect associated with a significant reduction in ATP synthesis. As a follow-up study, we have evaluated the ability of DHM to induce mitochondrial permeability transition (MPT) and its associated processes in isolated rat liver mitochondria. In the presence of 10 microM Ca(2+), DHM (50-250 microM) elicited MPT in a concentration-dependent, but cyclosporine A-independent manner, as assessed by mitochondrial swelling, which is associated with mitochondrial Ca(2+) efflux and cytochrome c release. DHM (50-250 microM) did not cause hydrogen peroxide accumulation but did deplete endogenous glutathione and NAD(P)H, while oxidizing protein thiol groups. These results potentially indicate the involvement of mitochondria, via apoptosis, in the well-documented cytotoxicity of monocrotaline.

Endothelial nitric oxide (NO) and its pathophysiologic regulation

Nitric oxide (NO) is a gaseous lipophilic free radical generated by three distinct isoforms of nitric oxide synthases (NOS), type 1 or neuronal (nNOS), type 2 or inducible (iNOS) and type 3 or endothelial NOS (eNOS). Expression of eNOS is altered in many types of cardiovascular disease, such as atherosclerosis, diabetes and hypertension. The ubiquitous chaperone heat shock protein 90 (hsp90) associates with NOS and is important for its proper folding and function. Current studies point toward a therapeutic potential by modulating hsp90-NOS association in various vascular diseases. Here we review the transcriptional regulation of endothelial NOS and factors affecting eNOS activity and function, as well as the important vascular pathologies associated with altered NOS function, focusing on the regulatory role of hsp90 and other factors in NO-associated pathogenesis of these diseases.

Inflammation, endothelial injury, and persistent pulmonary hypertension in heterozygous BMPR2-mutant mice

Heterozygous bone morphogenetic protein receptor-II-knockout (BMPR2(+/-)) mice have a similar genetic trait like that in some idiopathic pulmonary arterial hypertension patients. To examine the effect of pulmonary endothelial injury in BMPR2(+/-) mice, we challenged the mice with two injections of monocrotaline combined with intratracheal instillation of replication-deficient adenovirus expressing 5-lipoxygenase (MCT+Ad5LO). After the challenge (1 wk), BMPR2(+/-) mice exhibited a doubling of right ventricular systolic pressure that was greater than that of wild-type mice and remained elevated for 3 wk before heart failure developed. Muscularization and thickening of small pulmonary arterioles was evident in the BMPR2(+/-) lungs at 2 wk after the challenge and became severe at 3 wk. Marked perivascular infiltration of T cells, B cells, and macrophages was associated with the remodeled vessels. Real-time PCR analysis showed that the expression of six endothelial cell markers in lung tissue was decreased to 20-40% of original levels at 1 wk after the challenge in both BMPR2(+/-) and wild-type mice and largely recovered in wild-type (50-80%) but not BMPR2(+/-) lungs (30-50%) at 3 wk after the challenge. Macrophage inflammatory protein-1alpha and fractalkine receptor expression doubled in BMPR2(+/-) compared with wild-type lungs. Expression of type I and type II BMP receptors, but not transforming growth factor-beta receptors, in the challenged BMPR2(+/-) and wild-type lungs showed a similar pattern of expression as that of endothelial markers. Apoptotic responses at 1 wk after MCT and Ad5LO challenge were also significantly greater in the BMPR2(+/-) lungs than the wild-type lungs. These data show that BMPR2(+/-) mice are more sensitive to MCT+Ad5LO-induced pulmonary hypertension than wild-type mice. Greater endothelial injury and an enhanced inflammatory response could be the underlying causes of the sensitivity and may work in concert with BMPR2 heterozygosity to promote the development of persistent pulmonary hypertension.

Smad Signaling in the Rat Model of Monocrotaline Pulmonary Hypertension

Mutations in the bone morphogenetic protein receptor type II (BMPrII) gene have been implicated in the development of familial pulmonary artery hypertension (PAH). The function of BMP signal transduction within the pulmonary vasculature and the role BMPrII mutations have in the development of PAH are incompletely understood. We used the monocrotaline (MCT) model of PAH to examine alterations in Smad signal transduction pathways in vivo. Lungs harvested from Sprague-Dawley rats treated with a single 60-mg/kg intraperitoneal (IP) injection of MCT were compared to saline-treated controls 2 weeks following treatment. Smad 4 was localized by immunohistochemistry to endothelial nuclei of the intra-acinar vessels undergoing remodeling. Smad 4, common to both BMP and transforming growth factor β (TGFβ) signaling, and BMP-specific Smad 1 were significantly decreased in western blot from whole lungs of treated animals, while no change was found for TGFβ-specific Smad 2. MCT-treated rats also had increased expression of phosphorylated Smad 1 (P-Smad 1) but not phosphorylated Smad 2 (P-Smad 2). There was a decrease in the expression of the full BMPrII protein but not its short form variant in MCT-treated rat lungs. The type I receptor Alk1 had increased expression. Collectively, our data indicate that vascular remodeling in the MCT model is associated with alterations in BMP receptors and persistent endothelial Smad 1 signaling.

Dehydromonocrotaline inhibits mitochondrial complex I. A potential mechanism accounting for hepatotoxicity of monocrotaline

Monocrotaline is a pyrrolizidine alkaloid present in plants of the Crotalaria species, which causes cytotoxicity and genotoxicity, including hepatotoxicity in animals and humans. It is metabolized by cytochrome P-450 in the liver to the alkylating agent dehydromonocrotaline. We evaluated the effects of monocrotaline and its metabolite on respiration, membrane potential and ATP levels in isolated rat liver mitochondria, and on respiratory chain complex I NADH oxidase activity in submitochondrial particles. Dehydromonocrotaline, but not the parent compound, showed a concentration-dependent inhibition of glutamate/malate-supported state 3 respiration (respiratory chain complex I), but did not affect succinate-supported respiration (complex II). Only dehydromonocrotaline dissipated mitochondrial membrane potential, depleted ATP, and inhibited complex I NADH oxidase activity (IC50=62.06 microM) through a non-competitive type of inhibition (K(I)=8.1 microM). Therefore, dehydromonocrotaline is an inhibitor of the activity of respiratory chain complex I NADH oxidase, an action potentially accounting for the well-documented monocrotaline's hepatotoxicity to animals and humans. The mechanism probably involves change of the complex I conformation resulting from modification of cysteine thiol groups by the metabolite.