Maria Tiziana Corasaniti

S -nitrosylation regulates apoptosis

Nitric oxide (NO) modulates the biological activity of proteins by direct interactions with their iron centres. It can also S-nitrosylate cysteines to form S-nitrosothiols. Such reactions affect the activity of membrane-bound, cytosolic and nuclear proteins including the NMDA receptor, haemoglobin and transcription factors such as NF-κB and OxyR. NO is potentially toxic, inducing both apoptosis and necrosis. Here we show that NO-mediated S-nitrosylation of the cysteine-containing enzymes that mediate apoptosis (caspases and tissue-transglutaminase, tTG) regulates the balance between apoptosis and necrosis.

Post-ischemic brain damage: pathophysiology and role of inflammatory mediators

Neuroinflammatory mediators play a crucial role in the pathophysiology of brain ischemia, exerting either deleterious effects on the progression of tissue damage or beneficial roles during recovery and repair. Within hours after the ischemic insult, increased levels of cytokines and chemokines enhance the expression of adhesion molecules on cerebral endothelial cells, facilitating the adhesion and transendothelial migration of circulating neutrophils and monocytes. These cells may accumulate in the capillaries, further impairing cerebral blood flow, or extravasate into the brain parenchyma. Infiltrating leukocytes, as well as resident brain cells, including neurons and glia, may release pro‐inflammatory mediators, such as cytokines, chemokines and oxygen/nitrogen free radicals that contribute to the evolution of tissue damage. Moreover, recent studies have highlighted the involvement of matrix metalloproteinases in the propagation and regulation of neuroinflammatory responses to ischemic brain injury. These enzymes cleave protein components of the extracellular matrix such as collagen, proteoglycan and laminin, but also process a number of cell‐surface and soluble proteins, including receptors and cytokines such as interleukin‐1β. The present work reviewed the role of neuroinflammatory mediators in the pathophysiology of ischemic brain damage and their potential exploitation as drug targets for the treatment of cerebral ischemia.

Calpain-mediated cleavage of Beclin-1 and autophagy deregulation following retinal ischemic injury in vivo

Autophagy is the major intracellular degradation pathway that regulates long-lived proteins and organelles turnover. This process occurs at basal levels in all cells but it is rapidly upregulated in response to starvation and cellular stress. Although being recently implicated in neurodegeneration, it remains still unclear whether autophagy has a detrimental or protective role. In this study, we investigated the dynamics of the autophagic process in retinal tissue that has undergone transient ischemia, an experimental model that recapitulates features of ocular pathologies, including glaucoma, anterior ischemic optic neuropathy and retinal vessels occlusion. Retinal ischemia, induced in adult rats by increasing the intraocular pressure, was characterized by a reduction in the phosphatidylethanolamine-modified form of LC3 (LC3II) and by a significant decrease in Beclin-1. The latter event was associated with a proteolytic cleavage of Beclin-1, leading to the accumulation of a 50-kDa fragment. This event was prevented by intravitreal treatment with the non-competitive N-methyl-D-aspartate antagonist MK801 and calpain inhibitors or by calpain knockdown. Blockade of autophagy by pharmacological inhibition or Beclin-1 silencing in RGC-5 increased cell death, suggesting a pro-survival role of the autophagic process in this neuronal cell type. Altogether, our results provide original evidence for calpain-mediated cleavage of Beclin-1 and deregulation of basal autophagy in the rat retina that has undergone ocular ischemia/reperfusion injury.

Cell signaling pathways in the mechanisms of neuroprotection afforded by bergamot essential oil against NMDA-induced cell death in vitro

The effects of bergamot essential oil (BEO; Citrus bergamia, Risso) on excitotoxic neuronal damage was investigated in vitro.

BRAIN REGIONAL AND CELLULAR LOCALIZATION OF GELATINASE ACTIVITY IN RAT THAT HAVE UNDERGONE TRANSIENT MIDDLE CEREBRAL ARTERY OCCLUSION

Matrix metalloproteinases (MMPs) have been implicated in the pathophysiology of ischemic stroke. In particular, the gelatinases MMP-2 and MMP-9 contribute to disruption of the blood-brain barrier and hemorrhagic transformation following ischemic injury. In addition to extracellular matrix degradation, MMPs may directly regulate neuronal cell death through mechanisms that are not completely understood. Here we describe the spatio-temporal distribution of activated MMP-2 and MMP-9 in the brain of rats subjected to 2 h middle cerebral artery occlusion (MCAo) followed by different periods of reperfusion (15 min, 2 h, 6 h and 22 h). By in situ zymography we have observed that gelatinases become activated 15 min and 2 h after the beginning of reperfusion in the ischemic core and penumbra, respectively. In situ zymography signal broadly co-localized with NeuN-positive cells, thus suggesting that proteolysis mainly occurs in neurons. Gelatinolytic activity was mainly detected in cell nuclei, marginally appearing in the cytosol only at later stages following the insult; we did not detect variations in gelatinolysis in the extracellular matrix. Finally, we report that pharmacological inhibition of MMPs by N-[(2R)-2-(hydroxamidocarbonyl-methyl)-4-methylpenthanoyl]-L-tryptophan methylamide (GM6001) significantly reduces brain infarct volume induced by transient MCAo. Taken together our data underscore the crucial role of gelatinases during the early stages of reperfusion and further extend previous observations documenting the detrimental role of these enzymes in the pathophysiology of brain ischemia.

Estradiol reduces cytochrome c translocation and minimizes hippocampal damage caused by transient global ischemia in rat

It is well-established that 17beta-estradiol (17beta-E(2)) confers neuroprotection to male and female rats exposed to focal cerebral ischemia, while less is known about the effects of the hormone under conditions of transient global ischemia. Since translocation of cytochrome c from the mitochondria to the cytosol is a critical step in apoptotic cell death after cerebral ischemia, we have investigated whether 17beta-E(2) interferes with such mechanism to exert neuroprotection. Global ischemia, induced in male Wistar rats by 5-min 4 vessel occlusion (4VO), resulted in a significant increase of cytosolic cytochrome c (cyt-c) levels as detected by Western blotting at 6h after reperfusion. 17beta-E(2) (0.2mg/kg, i.p.) given 1h before ischemia minimized cytochrome c translocation and the latter effect was partially reversed by tamoxifen (0.25mg/kg, i.p.). Bilateral cell counting revealed that delayed hippocampal damage typically caused by 4VO was abolished by 17beta-E(2) and this was partially reversed by tamoxifen in the CA3 subregion, but not in CA1/CA2 or CA4. These findings provide the original observation that 17beta-E(2) reduces delayed hippocampal damage caused by 4VO in male rats and blocks cytochrome c translocation during the early stages of neuronal death, thus providing an important mechanism involved in estrogen-mediated neuroprotection.

Modulation of the endocannabinoid system by focal brain ischemia in the rat is involved in neuroprotection afforded by 17β-estradiol

Endogenous levels of the endocannabinoid anandamide, and the activities of the synthesizing and hydrolyzing enzymes, i.e. N‐acylphosphatidylethanolamine‐hydrolyzing phospholipase D and fatty acid amide hydrolase, respectively, were determined in the cortex and the striatum of rats subjected to transient middle cerebral artery occlusion. Anandamide content was markedly increased (∼ 3‐fold over controls; P < 0.01) in the ischemic striatum after 2 h of middle cerebral artery occlusion, but not in the cortex, and this elevation was paralleled by increased activity of N‐acylphosphatidylethanolamine‐hydrolyzing phospholipase D (∼ 1.7‐fold; P < 0.01), and reduced activity (∼ 0.6‐fold; P < 0.01) and expression (∼ 0.7‐fold; P < 0.05) of fatty acid amide hydrolase. These effects of middle cerebral artery occlusion were further potentiated by 1 h of reperfusion, whereas anandamide binding to type 1 cannabinoid and type 1 vanilloid receptors was not affected significantly by the ischemic insult. Additionally, the cannabinoid type 1 receptor antagonist SR141716, but not the receptor agonist R‐(+)‐WIN55,212‐2, significantly reduced (33%; P < 0.05) cerebral infarct volume detected 22 h after the beginning of reperfusion. A neuroprotective intraperitoneal dose of 17β‐estradiol (0.20 mg·kg−1) that reduced infarct size by 43% also minimized the effect of brain ischemia on the endocannabinoid system, in an estrogen receptor‐dependent manner. In conclusion, we show that the endocannabinoid system is implicated in the pathophysiology of transient middle cerebral artery occlusion‐induced brain damage, and that neuroprotection afforded by estrogen is coincident with a re‐establishment of anandamide levels in the ischemic striatum through a mechanism that needs to be investigated further.

Neurotoxic Effects Induced by Intracerebral and Systemic Injection of Paraquat in Rats

1 The neurotoxic effects elicited by paraquat after systemic and intracerebral injection were studied in rats. 2 Intrahippocampal microinfusion of paraquat (0.1 μmol) produced behavioural stimulation and electrocortical (ECoG) excitation followed, at 24 h, by multifocal brain damage. Similarly, microinfusion of paraquat (0.2-0.4 μmol) into the locus coeruleus, substantia nigra or into the raphe nuclei, where noradrenergic, dopaminergic and serotonergic neurons are present, respectively, elicited potent excitotoxic effects (n=6 rats per dose and area). A lower dose (0.01 μmol) of the herbicide or injection of the vehicle (1.0 μl) did not produce any behavioural, ECoG or neurodegenerative effect. 3 After systemic administration, paraquat (20 mg kg-1 s.c.) evoked limbic motor seizures and ECoG epileptogenic discharges; in 10 out of 15 treated rats neuronal cell death was observed in the pyriform cortex, but not in other brain regions. A dose of 5 mg kg-1 was ineffective. 4 Among the regions of the brain studied, high concentrations of paraquat were detected in the pyriform cortex 24 h after systemic administration (5.0 and 20 mg kg -1 s.c.) lower levels being observed in the caudate nucleus. 5 In conclusion, paraquat, given systemically or intracerebrally in rats produces neurodegenerative effects.

Intraplantar injection of bergamot essential oil induces peripheral antinociception mediated by opioid mechanism.

This study investigated the effect of bergamot essential oil (BEO) containing linalool and linalyl acetate as major volatile components in the capsaicin test. The intraplantar injection of capsaicin (1.6 μg) produced a short-lived licking/biting response toward the injected paw. The nociceptive behavioral response evoked by capsaicin was inhibited dose-dependently by intraplantar injection of BEO. Both linalool and linalyl acetate, injected into the hindpaw, showed a significant reduction of nociceptive response, which was much more potent than BEO. Intraperitoneal (i.p.) and intraplantar pretreatment with naloxone hydrochloride, an opioid receptor antagonist, significantly reversed BEO- and linalool-induced antinociception. Pretreatment with naloxone methiodide, a peripherally acting μ-opioid receptor preferring antagonist, resulted in a significant antagonizing effect on antinociception induced by BEO and linalool. Antinociception induced by i.p. or intrathecal morphine was enhanced by the combined injection of BEO or linalool. The enhanced effect of combination of BEO or linalool with morphine was antagonized by pretreatment with naloxone hydrochloride. Our results provide evidence for the involvement of peripheral opioids, in the antinociception induced by BEO and linalool. Combined administration of BEO or linalool acting at the peripheral site, and morphine may be a promising approach in the treatment of clinical pain.

17β-Estradiol prevents retinal ganglion cell loss induced by acute rise of intraocular pressure in rat

Glaucoma, is a progressive optic neuropathy often associated with increased intraocular pressure (IOP) and characterized by progressive death of retinal ganglion cells (RGCs). High acute rise of IOP is a model for retinal ischemia and may represent a model of acute angle closure glaucoma. Here we have used this experimental model in combination with a neurochemical and neuropathological approach to gain more insight in the neuroprotective profile of 17beta-estradiol (E2), a steroid hormone, which has been shown to increase the viability, survival, and differentiation of primary neuronal cultures from different brain areas including amygdala, hypothalamus, and neocortex. Our data demonstrate that systemic administration of E2 significantly reduces RGC loss induced by high IOP in rat. In addition, pretreatment with E2, 30 min before ischemia, minimizes the elevation of glutamate observed during the reperfusion period. These effects seem to be in part mediated by the activation of the estrogen receptor, since a pretreatment with ICI 182-780, a specific estrogen receptor antagonist, partially counteracts the neuroprotection afforded by the estrogen.