Administration of antisense DNA for hepatocyte growth factor causes an depressive and anxiogenic response in rats

Abstract

Hepatocyte growth factor (HGF) is induced in neurons during ischemia and is neuroprotective against post-ischemic delayed neuronal death in the hippocampus. HGF might play an important role in the maturation and functioning of these neurons in the hippocampus. Our aim was to determine what effect HGF antisense has on depression and anxiety in rats. HGF antisense was infused at a constant rate into cerebral lateral ventricles and its effect on anxiety in rats was monitored. In forced swimming test, rats that received antisense DNA increased the length of time that they were immobile in the water. In the elevated plus maze test, the black and white box test and conditioned fear test, HGF antisense administration caused all indicators of anxiety to increase. Number of HGF-positive cells in C1 of hippocampus was significantly decreased in the HGF antisense-infused group compared to the vehicle- and scrambled oligonucleotide-treated group. No significant effect on general locomotor activity was seen. These results indicate that inhibition of HGF induces an increase in depression and anxiety-related behaviors suggesting a depressive and anxiogenic-like effect.

Introduction

Hepatocyte growth factor (HGF) is a potent angiogenic growth factor (Morishita et al., 1999, Hayashi et al., 1999, Aoki et al., 2000), although it was originally described as a pleiotropic cytokine with mitogenic, motogenic, and morphogenic activities in a variety of cells (Nakamura et al., 1989). Recently, it was reported that HGF is induced in neurons during ischemia (Hayashi et al., 1999) and is neuroprotective against postischemic delayed neuronal death in the hippocampus (Miyazawa et al., 1998, Yamada et al., 1996). HGF also promotes neural induction, suggesting a broad role for this factor during early development (Streit et al., 1995). HGF and c-Met have been found to be present in the developing and in the mature central nervous system (Tashiro et al., 1990, Zarnegar and Michalopoulos, 1995, De Frances et al., 1992, Di Renzo et al., 1993, Jung et al., 1994, Honda et al., 1995, Hamanoue et al., 1996, Achim et al., 1997). Studies in vitro have shown that HGF is both a survival factor and a chemoattractant for spinal motoneurons in culture (Ebens et al., 1996). Subsequently, HGF was found to co-operate with ciliary neurotrophic factor in promoting motor neuron survival (Wong et al., 1997), and to act on a subpopulation of embryonic motoneurons increasing their survival (Yamamoto et al., 1997). In the peripheral nervous system, HGF promotes survival of dorsal root ganglion neurons in conjunction with nerve growth factor (NGF) (Maina et al., 1997). Recently, HGF/c-Met signaling was shown to have multiple and complex effects on cultured sympathetic neuroblasts-effects that are partly due to an autocrine stimulation of cells by HGF (Maina et al., 1998).

In brain, HGF is expressed by specific classes of neurons in addition to non-neuronal cells in the ependyma and choroid plexus (Jung et al., 1994). In contrast to HGF, c-Met transcripts have been predominantly localized in neurons of the cerebral cortex, hippocampus and septum (Jung et al., 1994, Honda et al., 1995, Achim et al., 1997). HGF elevated the proto-oncogene c-fos mRNA in cultured septal neurons, showing a functional interaction between c-Met and its ligand (Jung et al., 1994). This finding, together with the presence of c-Met in developing brain, raised the possibility that HGF may have a neurotrophic activity on central neurons. In keeping with this hypothesis, Hamanoue et al. (1996) showed that HGF promoted the survival of cultured mesencephalic tyrosine hydroxylase-positive neurons. HGF acts on calbindin D-containing hippocampal neurons and increases their neurite outgrowth, suggesting that HGF plays an important role in the maturation and function of hippocampal neurons (Korhonen et al., 2000). Transfection of HGF gene into the subarachnoid space prevented delayed neuronal death (DND), accompanied by a significant increase in HGF in the cerebrospinal fluid. Prevention of DND by HGF is due to the inhibition of apoptosis through the blockade of bax translocation from the cytoplasm to the nucleus. HGF gene transfer into the subarachnoid space may provide a new therapeutic strategy for cerebrovascular disease (Hayashi et al., 2001).

We already reported that HGF infusion into the lateral ventricle produced an anxiolytic effect in rats (Isogawa et al., 2005). This is the first report to determine what effect HGF antisense-infused into cerebral lateral ventricles has on depression and anxiety in rats.