Enhancement of PAI-1 mRNA in cardiovascular cells after kainate injection is mediated through the sympathetic nervous system.

Plasminogen activator inhibitor-1 (PAI-1) is a major physiological regulator of the fibrinolytic system and is thought to promote vascular diseases. Recently, we have reported that PAI-1 gene expression was markedly enhanced locally in cardiovascular cells immediately after injecting (i.p.) mice with kainate, an analog of glutamate, which is the principal excitatory neurotransmitter in the central nervous system. Here we investigated whether the induction of PAI-1 mRNA by kainate could be mediated through sympathetic versus parasympathetic efferent neurons. To this end, we used a group of drugs known to interfere with the aforementioned pathways. PAI-1 gene expression was monitored in the heart via in situ hybridization using (35)S-labeled PAI-1-specific riboprobes. We have found that the elevation of PAI-1 mRNA levels, as detected 3 h after systemic administration of kainate, was reduced by mecamylamine, guanethidine and phentolamine, but not by propranolol or atropine. In addition, the adrenergic agonists phenylephrine and adrenaline themselves, but not clonidine, induced PAI-1 with a spatial distribution similar to that of kainate (i.e. in coronary arteries throughout the heart, and in cardiocytes in the left ventricular and atrial myocardium). Collectively, these results show that kainate activated the PAI-1 gene in cardiovascular cells primarily through the sympathetic nervous system (SNS), via the alpha1-adrenergic receptor. Hence, the results suggest that PAI-1 is likely to be increased during enhanced sympathetic efferent neuronal activity, such as occurring in heart failure or cardiac hypertrophy. The results also reinforce the previously reported linkage of PAI-1 to physiological stress. Furthermore, to our knowledge, this is the first demonstration that glutamate can enhance gene expression in a peripheral tissue. Thus, these findings raise the possibility that glutamate, acting via the SNS, can affect cardiovascular homeostasis and pathology by modulating gene expression in cardiac myocytes and vascular cells.

Mitochondrion-mediated apoptosis is enhanced in long-lived alphaMUPA transgenic mice and calorically restricted wild-type mice.

Caloric restriction (CR) can extend the life-span of multiple species and is the only intervention known to attenuate aging in mammals. Mechanisms mediating the CR influence are as yet unclear. To get insight into these mechanisms we took advantage of alphaMUPA transgenic mice that have previously been reported to spontaneously eat less and live longer compared with their wild-type (WT) control. Here we report that mitochondria isolated from young adult alphaMUPA livers showed increased susceptibility to calcium-induced high-amplitude swelling, increased cytochrome c release and enhanced glutathione levels. Furthermore, young adult alphaMUPA mice showed significantly enhanced caspase-3 activity in liver homogenates, increased fraction of apoptotic hepatocytes, and a lower level of serum IGF-1. In addition, alphaMUPA mice showed a decreased rate of spontaneously occurring lung tumors at an old age. Short-term (8 weeks) calorically restricted WT mice also showed an increase of mitochondrial swelling and caspase-3 activity compared with ad libitum (AL) fed WT mice. These results provide the first indication that CR can enhance mitochondrion-mediated apoptotic capacity. Collectively, the results are consistent with the possibility that long lasting, moderately increased apoptotic capacity, possibly linked in part to IGF-1 and GSH modulation, could play a role in the CR-induced anti-aging influence in mice.

Plasminogen mRNA induction in the mouse brain after kainate excitation: codistribution with plasminogen activator inhibitor-2 (PAI-2) mRNA.

Plasminogen (Plg), which can be converted to the active protease plasmin by plasminogen activators, has been previously implicated in brain plasticity and in toxicity inflicted in hippocampal pyramidal neurons by kainate. Here we have localized Plg. mRNA through in situ hybridization in brain cryosections derived from normal adult mice or after kainate injection (i.p.). The results indicated that Plg mRNA was undetectable in the normal brain, but after kainate injection it was induced in neuronal cells in multiple, but specific areas, including layers II-III of the neocortex; the olfactory bulb, anterior olfactory nucleus, and the piriform cortex; the caudate/putamen and accumbens nucleus shell; throughout the amygdaloid complex; and in the CAI/CA3 subfields of the hippocampus. Interestingly, this distribution pattern coincided with what we have recently described for the plasminogen activator inhibitor-2 (PAI-2) mRNA, however differing from that of the plasminogen activator inhibitor-1 (PAI-1) mRNA, as also shown here. These results suggest that enhanced Plg gene expression could be involved in events associated with olfactory, striatal, and limbic structures. Furthermore, because PAI-2 is thought to intracellularly counteract cytotoxic events, our results raise the possibility that PAI-2 can act in the brain as an intracellular neuroprotector against potential plasmin-mediated toxicity.