Pharmacogenomics and therapeutic target validation in cerebral vasospasm

Protective effects of heme oxygenase-1 against MPP(+)-induced cytotoxicity in PC-12 cells

Heme oxygenase-1 (HO-1) catalyses the rate-limiting step of heme degradation to biliverdin, which is in turn reduced to bilirubin, CO and free iron. HO-1 can be induced by several harmful stimuli including oxidative stress, and it has a protective role against the cytotoxicity in different cells. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridinium (MPP(+)) is a neurotoxic substance that induces the degeneration of dopaminergic neurons. This study examined whether HO-1 can be induced by MPP(+) and whether HO-1 has a protective role against the MPP(+)-induced cytotoxicity in PC-12 cells. MPP(+) triggered a relatively rapid induction of HO-1. The MPP(+)-induced cytotoxicity and reactive oxygen species (ROS) production markedly increased by HO-1 inhibitor, zinc protoporphyrin-IX (ZnPP-IX). The increase of ROS production by ZnPP-IX was completely abrogated by either two products of HO (biliverdin or bilirubin) while the increase of cytotoxicity by ZnPP-IX was attenuated partially. These suggest that HO-1 expression might have some cytoprotective effect against MPP(+)-induced cytotoxicity.

Pharmacogenomics of cardiovascular pharmacology: pharmacogenomic network of cardiovascular disease models

The most important strategies in pharmacogenomics are gene expression profiling and the network analysis of human disease models. We have previously discovered novel drug target candidates in cardiovascular diseases through investigations of these pharmacogenomics. The significant induction of S100C mRNA and protein expression was detected in the rat pulmonary hypertension and myocardial infarction model. We also found increased taurine in hypoxia, a calcium-associated cytoprotective compound, to suppress the hypoxia-induced S100C gene expression and vascular remodeling. These results suggest that S100C may be one of the potential novel drug targets in hypoxic or ischemic diseases. Delayed cerebral vasospasm after aneurysmal subarachnoid hemorrhage causes cerebral ischemia and infarction. Using a DNA microarray, a prominant upregulation of heme oxygenase-1 (HO-1) and heat shock protein (HSP) 72 mRNAs were observed in the basilar artery of a murine vasospasm model. Antisense HO-1 and HSP 72 oligodeoxynucleotide inhibited HO-1 and HSP 72 induction, respectively, and significantly aggravated cerebral vasospasm. Moreover, we have also developed a unique heart failure model in zebrafish and identified several candidate genes as novel drug targets. These results suggest that pharmacogenomic network analysis has the potential to bridge the gap between in vitro and in vivo studies and could define strategies for identifying novel drug targets in various cardiovascular diseases.

Heme regulation in traumatic brain injury: relevance to the adult and developing brain

Intracranial bleeding is one of the most prominent aspects in the clinical diagnosis and prognosis of traumatic brain injury (TBI). Substantial amounts of blood products, such as heme, are released because of traumatic subarachnoid hemorrhages, intraparenchymal contusions, and hematomas. Despite this, surprisingly few studies have directly addressed the role of blood products, in particular heme, in the setting of TBI. Heme is degraded by heme oxygenase (HO) into three highly bioactive products: iron, bilirubin, and carbon monoxide. The HO isozymes, in particular HO-1 and HO-2, exhibit significantly different expression patterns and appear to have specific roles after injury. Developmentally, differences between the adult and immature brain have implications for endogenous protection from oxidative stress. The aim of this paper is to review recent advances in the understanding of heme regulation and metabolism after brain injury and its specific relevance to the developing brain. These findings suggest novel clinical therapeutic options for further translational study.

Prediction of Cerebral Vasospasm in Patients Presenting with Aneurysmal Subarachnoid Hemorrhage: A Review

OBJECTIVE:

Cerebral vasospasm is a devastating medical complication of aneurysmal subarachnoid hemorrhage (SAH). It is associated with high morbidity and mortality rates, even after the aneurysm has been treated. A substantial amount of experimental and clinical research has been conducted in an effort to predict and prevent its occurrence. This research has contributed to significant advances in the understanding of the mechanisms leading to cerebral vasospasm. The ability to accurately and consistently predict the onset of cerebral vasospasm, however, has been challenging. This topic review describes the various methodologies and approaches that have been studied in an effort to predict the occurrence of cerebral vasospasm in patients presenting with SAH.

METHODS:

The English-language literature on the prediction of cerebral vasospasm after aneurysmal SAH was reviewed using the MEDLINE PubMed (1966–present) database.

RESULTS:

The risk factors, diagnostic imaging, bedside monitoring approaches, and pathological markers that have been evaluated to predict the occurrence of cerebral vasospasm after SAH are presented.

CONCLUSION:

To date, a large blood burden is the only consistently demonstrated risk factor for the prediction of cerebral vasospasm after SAH. Because vasospasm is such a multifactorial problem, attempts to predict its occurrence will probably require several different approaches and methodologies, as is done at present. Future improvements in the prevention of cerebral vasospasm from aneurysmal SAH will most likely require advances in our understanding of its pathophysiology and our ability to predict its onset.

Heme oxygenase expression in human central nervous system disorders

In the normal mammalian CNS, heme oxygenase-2 (HO-2) is constitutively, abundantly, and fairly ubiquitously expressed, whereas heme oxygenase-1 (HO-1) mRNA and protein are confined to small populations of scattered neurons and neuroglia. Unlike ho-2, the ho-1 gene in neural (and many systemic) tissues is exquisitely sensitive to upregulation by a host of pro-oxidant and other noxious stimuli. In Alzheimer disease, HO-1 immunoreactivity is significantly augmented in neurons and astrocytes of the hippocampus and cerebral cortex relative to age-matched, nondemented controls and colocalizes to senile plaques, neurofibrillary tangles, and corpora amylacea. In Parkinson disease, HO-1 decorates Lewy bodies of affected dopaminergic neurons and is highly overexpressed in astrocytes residing within the substantia nigra. The ho-1 gene is also upregulated in glial cells within multiple sclerosis plaques; in the vicinity of human cerebral infarcts, hemorrhages, and contusions; and in various other degenerative and nondegenerative human CNS disorders. The products of the heme oxygenase reaction, free ferrous iron, carbon monoxide, and biliverdin/bilirubin, are all biologically active molecules that may profoundly influence tissue redox homeostasis under a wide range of pathophysiological conditions. Evidence adduced from whole animal and in vitro studies indicates that enhanced HO-1 activity may either ameliorate or exacerbate neural injury, effects likely contingent upon the specific model employed, the duration and intensity of HO-1 induction, and the chemistry of the local redox microenvironment. HO-1 hyperactivity also promotes mitochondrial sequestration of nontransferrin iron in oxidatively challenged astroglia and may thereby contribute to the pathological iron deposition and bioenergetic failure amply documented in aging and degenerating human neural tissues.

Pharmacogenomics: the frontiers of genome medicine

The Human Genome Project provides insights so profound that it has the ability to change everything we know about medicine and how medicines are developed. Pharmacogenomics is defined as studies to identify the genes that are involved in determining the responsiveness to a given drug and to distinguish responders and non-responders to a given drug. Genome sequencing, transcriptome, and proteome analysis are of particular significance in pharmacogenomics. Transcriptome analysis can be done by methods of random cDNA sequencing, mRNA display and, differential hybridization (i.e., cDNA microarray and associated methods). Our results suggest that the pharmacogenomic transcriptome analysis and pharmainformatics have potential as strategies for defining novel drug targets in various diseases. Pharmacogenomics enhances the development, commercialization, and clinical use of conventional pharmaceutical products for common diseases, and it will eventually become a powerful tool for Evidence-Based Medicine. It is also important to predict interindividual pharmacokinetic differences by genetic polymorphisms of transporters or pharmacokinetic changes by transporter-mediated drug interactions during drug development. Pharmacogenomics and pharmainformatics enable us to move quickly and efficiently from targets to appropriate medicines.