The role of eNOS phosphorylation in causing drug-induced vascular injury

Clinical Applications for Gasotransmitters in the Cardiovascular System: Are We There Yet?

Ischemia is the underlying mechanism in a wide variety of acute and persistent pathologies. As such, understanding the fine intracellular events occurring during (and after) the restriction of blood supply is pivotal to improving the outcomes in clinical settings. Among others, gaseous signaling molecules constitutively produced by mammalian cells (gasotransmitters) have been shown to be of potential interest for clinical treatment of ischemia/reperfusion injury. Nitric oxide (NO and its sibling, HNO), hydrogen sulfide (H2S), and carbon monoxide (CO) have long been proven to be cytoprotective in basic science experiments, and they are now awaiting confirmation with clinical trials. The aim of this work is to review the literature and the clinical trials database to address the state of development of potential therapeutic applications for NO, H2S, and CO and the clinical scenarios where they are more promising.

Evaluation of in vivo MRI for detecting midodrine-induced arteritis in rats

There are no specific and sensitive biomarkers for arteritis, and the occurrence of arteritis in nonclinical toxicological studies of a candidate drug makes development of the drug very difficult. However, we showed in a previous study that the high signal intensity region around the artery on magnetic resonance imaging (MRI) could be a candidate biomarker for detection of arteritis. The present study was conducted to clarify the details of midodrine hydrochloride (MH)-induced arteritis lesions and whether arteritis induced by a mechanism other than the vasodilatory effect, which was evaluated in a previous study, could be detected by MRI. MH is a selective peripherally acting alpha-1 adrenergic receptor agonist, known to induce arteritis due to its vasoconstrictor action, but there is not enough information about MH-induced arteritis. Based on the data obtained under multiple dosing conditions, MH was administered subcutaneously to each rat once daily for 2 days at a dose level of 40 mg/kg/day for MRI assessment. The mesenteric arteries were examined using in vivo MRI at 1 day or 7 days after administration of the final dose and examined histopathologically. On the day after the final dose, high signal intensity region around the artery was observed in animals with minimal perivascular lesions confirmed by histopathology and not observed in an animal without histological changes. On the 7th day after the final dose, no abnormality was observed in histopathological examinations and no high signal intensity regions were observed by MRI in any animal. In conclusion, although further investigation is needed to confirm that high signal intensity is a reliable biomarker for humans, it is suggested that high signal intensity around the artery could be a versatile candidate biomarker with high specificity and sensitivity.

Safety issues of compounds acting on adenosinergic signalling

OBJECTIVES

Much research has been performed on the field of identifying the roles of adenosine and adenosinergic signalling, but a relatively low number of marketing authorizations have been granted for adenosine receptor (AdR) ligands. In part, this could be related to their safety issues; therefore, our aim was to examine the toxicological and adverse effects data of different compounds acting on adenosinergic signalling, including different AdR ligands and compounds resembling the structure of adenosine. We also wanted to present recent pharmaceutical developments of experimental compounds that showed promising results in clinical trial setting.

KEY FINDINGS

Safety issues of compounds modulating adenosinergic signalling were investigated, and different mechanisms were presented. Structurally different classes of compounds act on AdRs, the most important being adenosine, adenosine derivatives and other non-nucleoside compounds. Many of them are either not selective enough or are targeting other targets of adenosinergic signalling such as metabolizing enzymes that regulate adenosine levels. Many other targets are also involved that are not part of adenosinergic signalling system such as GABA receptors, different channels, enzymes and others. Some synthetic AdR ligands even showed to be genotoxic.

SUMMARY

Current review presents safety data of adenosine, adenosine derivatives and other non-nucleoside compounds that modulate adenosinergic signalling. We have presented different mechanisms that participate to an adverse effect or toxic outcome. A separate section also deals with possible organ-specific toxic effects on different in-vitro and in-vivo models.

Nitric oxide: what's new to NO?

Nitric oxide (NO) is one of the critical components of the vasculature, regulating key signaling pathways in health. In macrovessels, NO functions to suppress cell inflammation as well as adhesion. In this way, it inhibits thrombosis and promotes blood flow. It also functions to limit vessel constriction and vessel wall remodeling. In microvessels and particularly capillaries, NO, along with growth factors, is important in promoting new vessel formation, a process termed angiogenesis. With age and cardiovascular disease, animal and human studies confirm that NO is dysregulated at multiple levels including decreased production, decreased tissue half-life, and decreased potency. NO has also been implicated in diseases that are related to neurotransmission and cancer although it is likely that these processes involve NO at higher concentrations and from nonvascular cell sources. Conversely, NO and drugs that directly or indirectly increase NO signaling have found clinical applications in both age-related diseases and in younger individuals. This focused review considers recently reported advances being made in the field of NO signaling regulation at several levels including enzymatic production, receptor function, interacting partners, localization of signaling, matrix-cellular and cell-to-cell cross talk, as well as the possible impact these newly described mechanisms have on health and disease.

Sampling the Rat Mesenteric Artery

Vascular injury can be induced by different classes of drug candidates, and it can affect the mesenteric vasculature. Sampling of the mesenteric vessels in the rat is crucial for proper assessment of potential adverse or pharmacologic effects of drugs in nonclinical rodent studies. To date, several sampling and processing techniques for the histopathologic evaluation of the mesenteric artery in rodents have been described and used in studies with candidate drugs that may affect the vascular system. However, most of those techniques require a significant amount of time and effort. A less labor-intensive, time-consuming, and expensive technique that allows examination of the mesentery vasculature with abundant longitudinal and cross sections of the vessels when examined microscopically was developed and presented here.

An in vivo and in vitro study: High-dosage Danshen injection induces peripheral vascular endothelial cells injury

Danshen injection, a pharmaceutical dosage form of Danshen, has been widely used in the treatment of coronary heart diseases, myocardial infarction, and hypertension. With more and more adverse drug reactions linked with Danshen injection, its safety comes under suspicion. To evaluate its safety, mice were divided into four groups: vehicle, low-, middle-, and high-Danshen group, and each group was intravenously administered with Danshen injection at a dose of 0, 0.64, 1.55, and 5.76 g/kg/day for 5 days, respectively (the low dosage was the recommended clinical dosage, the middle dosage was the most commonly used higher dosage, and the high dosage was the highest dosage used in clinic). Peripheral vascular toxicity wasn't observed in the low-dosage group, elevated serum endothelin-1 (ET-1) was observed in the middle-dosage group; and more peripheral vascular toxicities like increased vascular leakage, elevated serum nitrate and ET-1, and vascular endothelial cells apoptosis were detected in the high-dosage group. In vitro study, low-concentration Danshen injection showed protective effect to human umbilical vein endothelial cells (HUVECs), while high concentration displayed strong cytotoxic effects, including increase in nitric oxide and ET-1 production, inhibition of cell viability, and apoptosis induction. Further, the HUVECs' apoptosis induced by high-concentration Danshen injection was found along with the induction of reactive oxygen species. In conclusion, these results suggest that Danshen injection is nontoxic in its recommended clinical dosage, and the 2.4-fold as the recommended clinical dosage might be the highest safety dosage in clinic treatment. In addition, Danshen injection is a potential vascular toxic drug in its high dosage and shouldn't be used far beyond its recommended dosage in clinic treatment.

Tissue-engineered blood vessels as promising tools for testing drug toxicity

Drug-induced vascular injury (DIVI) is a serious problem in preclinical studies of vasoactive molecules and for survivors of pediatric cancers. DIVI is often observed in rodents and some larger animals, primarily with drugs affecting vascular tone, but not in humans; however, DIVI observed in animal studies often precludes a drug candidate from continuing along the development pipeline. Thus, there is great interest by the pharmaceutical industry to identify quantifiable human biomarkers of DIVI. Small-scale endothelialized tissue-engineered blood vessels using human cells represent a promising approach to screen drug candidates and develop alternatives to cancer therapeutics in vitro. We identify several technical challenges that remain to be addressed, including high-throughput systems to screen large numbers of candidates, identification of suitable cell sources and establishing and maintaining a differentiated state of the vessel wall cells. Adequately addressing these challenges should yield novel platforms to screen drugs and develop new therapeutics to treat cardiovascular disease.

Scientific and Regulatory Policy Committee Points-to-consider Paper*

Drug-induced vascular injury (DIVI) is a recurrent challenge in the development of novel pharmaceutical agents. Although DIVI in laboratory animal species has been well characterized for vasoactive small molecules, there is little available information regarding DIVI associated with biotherapeutics such as peptides/proteins or antibodies. Because of the uncertainty about whether DIVI in preclinical studies is predictive of effects in humans and the lack of robust biomarkers of DIVI, preclinical DIVI findings can cause considerable delays in or even halt development of promising new drugs. This review discusses standard terminology, characteristics, and mechanisms of DIVI associated with biotherapeutics. Guidance and points to consider for the toxicologist and pathologist facing preclinical cases of biotherapeutic-related DIVI are outlined, and examples of regulatory feedback for each of the mechanistic types of DIVI are included to provide insight into risk assessment.

Proceedings of the 2014 National Toxicology Program Satellite Symposium

The 2014 annual National Toxicology Program (NTP) Satellite Symposium, entitled "Pathology Potpourri" was held in Washington, D.C., in advance of the Society of Toxicologic Pathology's 33rd annual meeting. The goal of this annual NTP Symposium is to present current diagnostic pathology or nomenclature issues to the toxicologic pathology community. This article presents summaries of the speakers' presentations, including diagnostic or nomenclature issues that were presented, along with select images that were used for audience voting and discussion. Some lesions and topics covered during the symposium included a pulmonary mucinous adenocarcinoma in a male B6C3F1 mouse; plexiform vasculopathy in Wistar Han (Crl:WI[Han]) rats; staging of the estrous cycle in rats and mice; peri-islet fibrosis, hemorrhage, lobular atrophy and inflammation in male Sprague-Dawley (SD) rats; retinal dysplasia in Crl:WI[Han] rats and B6C3F1 mice; multicentric lymphoma with intravascular microemboli and tumor lysis syndrome, and 2 cases of myopathy and vascular anomaly in Tg.rasH2 mice; benign thymomas in Crl:WI[Han] rats; angiomatous lesions in the mesenteric lymph nodes of Crl:WI[Han] rats; an unusual foveal lesion in a cynomolgous monkey; and finally a series of nomenclatures challenges from the endocrine International Harmonization of Nomenclature and Diagnostic Criteria (INHAND) Organ Working Group (OWG).

Nonclinical Safety Biomarkers of Drug-induced Vascular Injury

Better biomarkers are needed to identify, characterize, and/or monitor drug-induced vascular injury (DIVI) in nonclinical species and patients. The Predictive Safety Testing Consortium (PSTC), a precompetitive collaboration of pharmaceutical companies and the U.S. Food and Drug Administration (FDA), formed the Vascular Injury Working Group (VIWG) to develop and qualify translatable biomarkers of DIVI. The VIWG focused its research on acute DIVI because early detection for clinical and nonclinical safety monitoring is desirable. The VIWG developed a strategy based on the premise that biomarkers of DIVI in rat would be translatable to humans due to the morphologic similarity of vascular injury between species regardless of mechanism. The histomorphologic lexicon for DIVI in rat defines degenerative and adaptive findings of the vascular endothelium and smooth muscles, and characterizes inflammatory components. We describe the mechanisms of these changes and their associations with candidate biomarkers for which advanced analytical method validation was completed. Further development is recommended for circulating microRNAs, endothelial microparticles, and imaging techniques. Recommendations for sample collection and processing, analytical methods, and confirmation of target localization using immunohistochemistry and in situ hybridization are described. The methods described are anticipated to aid in the identification and qualification of translational biomarkers for DIVI.