Neuronal‐NOS adaptor protein expression after spreading depression: implications for NO production and ischemic tolerance

Abstract

Cortical spreading depression (CSD) is characterized by slowly propagating waves of neuronal/astrocytic depolarization and metabolic changes, followed by a period of quiescent neuronal and electroencephalographic activity. CSD acts as a preconditioning stimulus in brain, reducing cell death when elicited up to several days prior to an ischemic insult. Precise mechanisms associated with this neuroprotection are not known, although CSD increases the expression of a number of potentially neuroprotective genes/proteins. The nitric oxide (NO) system may be of particular importance, as it is acutely activated and chronically up-regulated in cerebral cortex by CSD, and NO can ameliorate and exacerbate cell death under different conditions. Several molecules have recently been identified that modulate the production and/or cellular actions of NO, but it is not known whether their expression is altered by CSD. Therefore, the present study examined the effect of CSD on the spatiotemporal expression of PIN, CAPON, PSD-95, Mn-SOD and Cu/Zn-SOD mRNA in the rat brain. In situ hybridization using specific [35 S]-labelled oligonucleotides revealed that levels of PIN mRNA were significantly increased in the cortex and claustrum (30-180%; p £ 0.01) after 6 h and 1 and 2 days, but were again equivalent to contralateral (control) cortical values at 7, 14 and 28 days. CAPON mRNA levels were increased (30-180%; p £ 0.05) in the ipsilateral cortical hemisphere at 6 h and 2 days post treatment, but not at the other times examined. In contrast, levels of PSD-95, Mn-and Cu/Zn-SOD mRNA were not altered at any time after CSD. These results suggest that following CSD, nNOS activity and NO levels may be tightly regulated by both transcriptional and translational alterations in a range of nNOS adaptor proteins, which may contribute to CSD-induced neuroprotection against subsequent ischemia. Obrenovitch et al. 2002). CSD alone does not cause neuronal damage or loss, even when elicited for 4-5 h (Nedergaard and Hansen 1988), but when it occurs in haemodynamically or metabolically compromised tissue, the additional metabolic load induced potentiates the degree of cell damage, both in vivo and in vitro (Back et al. 1996;Busch et al. 1996;Obeidat and Andrew 1998). In contrast, an episode of CSD elicited 1-14 days prior to an ischemic insult significantly reduces Abbreviations used: CAPON, carboxy-terminal PDZ ligand of nNOS; CSD, cortical spreading depression; DHC, dynein heavy-chain; KLC, kinesin light-chain; Mn(Cu/Zn)-SOD, manganese (zinc/copper)-containing isoform of superoxide dismutase; NO, nitric oxide; nNOS, neuronal nitric oxide synthase; PDZ, postsynaptic-density zone; PIN, protein inhibitor of neuronal nitric oxide synthase; PSD-95, postsynaptic density-95; SSC, saline sodium citrate.

Nitric Oxide Synthase (NOS)-Interacting Protein Interacts with Neuronal NOS and Regulates Its Distribution and Activity

“…These results, together with the negative modulation of NOS function by NOSIP, suggest that an activity-dependent upregulation of NOSIP may constitute a protective or compensatory mechanism to counteract excessive production of NO in neurons. Interestingly, this kind of modulation is not unique for NOSIP but is a feature shared by several other proteins interacting with nNOS, including CAPON, PIN, and PSD-95, which are known to be upregulated in models of enhanced neuronal activity and pathology in the central and peripheral nervous systems (Che et al, 2000a,b;Ohnuma et al, 2000;Jiang et al, 2003;Wiggins et al, 2003). Thus, nNOS is likely subject to tight regulatory control via activity-dependent modifications in the expression of several nNOS-interacting proteins.…”

“…The expression of nNOS as well as its interacting proteins such as CAPON, PIN (protein inhibitor of NOS), and PSD-95 has been reported to be upregulated by stimuli triggering long-lasting activation of neurons in the central and peripheral nervous systems (Che et al, 2000a,b;Huh et al, 2000;Lumme et al, 2000;Ohnuma et al, 2000;Sasaki et al, 2000;Jiang et al, 2003;Wiggins et al, 2003). We therefore asked whether the expression of NOSIP is also regulated by neuronal activity in vivo and in vitro.…”

Molecular Physiology of Preconditioning-Induced Brain Tolerance to Ischemia

“…When brain preconditioning was induced in gerbils by an oxidative stress (287) or in rats by LPS (41), SOD brain activity increased with ischemic tolerance. Finally, CSD is a robust stimulus for brain preconditioning, but two separate studies with rats clearly suggested that CSD-induced ischemic tolerance was not mediated through the upregulation of SODs (253,433).…”

A novel endogenous erythropoietin mediated pathway prevents axonal degeneration

“…42,43 Although NO-mediated neurotoxicity has been explored by several groups over the years, NOmediated neuroprotection is poorly understood. In our study, nNOS inhibition exacerbates the axonal degeneration induced by gp120.…”