Acetaminophen reduces mitochondrial dysfunction during early cerebral postischemic reperfusion in rats

Role of PI3K/Akt axis in mitigating hippocampal ischemia-reperfusion injury via CB1 receptor stimulation by paracetamol and FAAH inhibitor in rat

AIMS

Acetaminophen or paracetamol (PAR), the recommended antipyretic in COVID-19 and clinically used to alleviate stroke-associated hyperthermia interestingly activates cannabinoid receptor (CB1) through its AM404 metabolite, however, to date, no study reports the in vivo activation of PAR/AM404/CB1 axis in stroke. The current study deciphers the neuroprotective effect of PAR in cerebral ischemia/reperfusion (IR) rat model and unmasks its link with AM404/CB1/PI3K/Akt axis.

MATERIALS AND METHODS

Animals were allocated into 5 groups: (I) sham-operated (SO), (II) IR, (III) IR + PAR (100 mg/kg), (IV) IR + PAR (100 mg/kg) + URB597; anandamide degradation inhibitor (0.3 mg/kg) and (V) IR + PAR (100 mg/kg) + AM4113; CB1 Blocker (5 mg/kg). All drugs were intraperitoneally administered at the inception of the reperfusion period.

KEY FINDINGS

PAR administration alleviated the cognitive impairment in the Morris Water Maze as well as hippocampal histopathological and immunohistochemical examination of GFAP. The PAR signaling was associated with elevation of anandamide level, CB1 receptor expression and survival proteins as p^S473-Akt. P^{(tyr202/thr204)}-ERK1/2 and p^S9-GSK3β. Simultaneously, PAR increased hippocampal BDNF and ß-arrestin1 levels and decreased glutamate level. PAR restores the deranged redox milieu induced by IR Injury, by reducing lipid peroxides, myeloperoxidase activity and NF-κB and increasing NPSH, total antioxidant capacity, nitric oxide and Nrf2 levels. The pre-administration of AM4113 reversed PAR effects, while URB597 potentiated them.

SIGNIFICANCE

PAR poses a significant neuroprotective effect which may be mediated, at least in part, via activation of anandamide/CB1/PI3K/Akt pathway in the IR rat model.

Astilbin ameliorates oxidative stress and apoptosis in D-galactose-induced senescence by regulating the PI3K/Akt/m-TOR signaling pathway in the brains of mice

An increasing amount of evidence has shown that injection of D-galactose (D-gal) can mimic natural aging that typically is associated with brain injury. Oxidative stress and apoptosis has been shown to play an essential role in aging process. The purpose of this study was to investigate the protective effectsof astilbin (ASB) on D-Gal-induced agingin miceand to further explore the underlying mechanisms. We randomly divided 50 mice into 5 groups.To establish this model of aging, 40micewere intraperitoneally administered D-Gal (500 mg/kg). The mice in the treatmentgroupswere intragastricaly administratedASB at doses of 40 and 80 mg/kg. H&E and TUNEL staining were used to determine the effect of ASB on the number of apoptotic cells in the brain. Furthermore, biochemical indices of serum, oxidative stress factors, and apoptosis factors were determined to clarify the underlying mechanism using reagent test kits and western blotting. The results showed that varying doses of ASB could improve D-Gal-induced histopathological damageand significantly alleviatedthe aging induced by D-Galin mice. ASB remarkably decreased the activities of malondialdehyde (MDA)(p < 0.01)and Acetyl cholinesterase (AChE)(p < 0.05) and markedlyincreased the content of catalase (CAT)(p < 0.01)and superoxide dismutase (SOD)(p < 0.01), respectively. In addition, Western blotting revealed thatASB treatment (40 mg/kg)attenuated the D-gal-induced Bax and Caspase 3 protein expression(p < 0.01) and reversed the increase in Bcl-2protein expressionin brain. Moreover, ASB treatment significantly upregulated the protein expression ofp-PI3K/PI3K and altered the p-Akt/Akt ratio (p < 0.05), while inhibiting the expression of p-m-TOR relative to m-TOR(p < 0.05). Moreover, the expression of P53 tended to decreasein the low ASB treatmentgroup (40 mg/kg), whereas no change was observed in the high ASB treatmentgroup (80 mg/kg). In the intestinal flora, the richness of the normal group and the ASB group was higher than that of the D-Gal group. Heat map analysis also showed that ASB promoted Lactobacillus and other probiotics and also confirmed the advantages of ASB. The observed changes in intestinal flora further verified the efficacy of ASB.

Mechanistic insights into the protective effect of paracetamol against rotenone-induced Parkinson's disease in rats: Possible role of endocannabinoid system modulation

Parkinson's disease (PD) is a disabling progressive neurodegenerative disease. So far, PD's treatment remains symptomatic with no curative effects. Aside from its blatant analgesic and antipyretic efficacy, recent studies highlighted the endowed neuroprotective potentials of paracetamol (PCM). To this end: the present study investigated: (1) Possible protective role of PCM against rotenone-induced PD-like neurotoxicity in rats, and (2) the mechanisms underlying its neuroprotective actions including cannabinoid receptors' modulation. A dose-response study was conducted using three doses of PCM (25, 50, and 100 mg/kg/day, i.p.) and their effects on body weight changes, spontaneous locomotor activity, rotarod test, tyrosine hydroxylase (TH) and α-synuclein expression, and striatal dopamine (DA) content were evaluated. Results revealed that PCM (100 mg/kg/day, i.p.) halted PD motor impairment, prevented rotenone-induced weight loss, restored normal histological tissue structure, reversed rotenone-induced reduction in TH expression and striatal DA content, and markedly decreased midbrain and striatal α-synuclein expression in rotenone-treated rats. Accordingly, PCM (100 mg/kg/day, i.p.) was selected for further mechanistic investigations, where it ameliorated rotenone-induced oxidative stress, neuro-inflammation, apoptosis, and disturbed cannabinoid receptors' expression. In conclusion, our findings imply a multi-target neuroprotective effect of PCM in PD which could be attributed to its antioxidant, anti-inflammatory and anti-apoptotic activities, in addition to cannabinoid receptors' modulation.

Comparison of effects of high and low dose paracetamol treatment and toxicity on brain and liver in rats

OBJECTIVE

Paracetamol is thought that it acts by inhibiting the central cyclooxygenase (COX) enzyme; its mechanism of action is still not fully explained. Although its most important side effect is hepatoxicity, it is thought to cause toxicity on the brain in recent years. The present study aims to investigate the treatment and toxic effects of low and high doses of paracetamol on the liver and brain.

METHODS

Wistar-albino rats were used in this study. At doses of 20-500 mg/kg, paracetamol was administered intraperitoneally once a day for one and three days. The brain and liver were used for immunohistochemical evaluation using COX-3, prostaglandin E₂ (PGE₂) and caspase 3 antibodies and for total antioxidant (TAS), total oxidant (TOS) and oxidative stress index (OSI) measurements. Results were evaluated using the Kruskal Wallis test (SPSS ver.24).

RESULTS

The liver COX-3 levels were significantly lower in both groups with higher doses (p<0.05). In the brain, there was no statistically significant difference in COX-3 levels between the groups. There was no statistically significant difference in PGE₂ levels in the liver and brain between the groups (p>0.05). The caspase 3 level in the liver was statistically significantly higher in the low dose group compared to the other groups (p<0.05). In both liver and brain, OSI values were significantly higher in the 3-day high-dose group compared to others (p<0.05). There was no statistically significant difference between the groups in ALT and AST values (p>0.05).

CONCLUSION

The results of our study show that paracetamol inhibits the COX-3 enzyme in the liver but has no effect in the brain, and COX-3 does not have an effect on PGE₂. Paracetamol causes apoptosis in the liver only in low doses; higher doses may cause toxicity by increasing oxidative stress, especially in the brain.

Acetaminophen Mitigates Myocardial Injury Induced by Lower Extremity Ischemia-Reperfusion in Rat Model

OBJECTIVE

The injury-reducing effect of acetaminophen, an effective analgesic and antipyretic on ischemia-reperfusion continues to attract great attention. This study analyzed the protective effect of acetaminophen on myocardial injury induced by ischemia-reperfusion in an experimental animal model from lower extremity ischemia-reperfusion.

METHODS

Twenty-four Sprague-Dawley female rats were randomized into three groups (n=8) as (i) control group (only laparotomy), (ii) aortic ischemia-reperfusion group (60 min of ischemia and 120 min of reperfusion) and (iii) ischemia-reperfusion + acetaminophen group (15 mg/kg/h intravenous acetaminophen infusion starting 15 minutes before the end of the ischemic period and lasting till the end of the reperfusion period). Sternotomy was performed in all groups at the end of the reperfusion period and the heart was removed for histopathological examination. The removed hearts were histopathologically investigated for myocytolysis, polymorphonuclear leukocyte (PMNL) infiltration, myofibrillar edema and focal hemorrhage.

RESULTS

The results of histopathological examination showed that acetaminophen was detected to particularly diminish focal hemorrhage and myofibrillar edema in the ischemia-reperfusion + acetaminophen group (P<0.001, P=0.011), while there were no effects on myocytolysis and PMNL infiltration between the groups (P=1.000, P=0.124).

CONCLUSION

Acetaminophen is considered to have cardioprotective effect in rats, by reducing myocardial injury induced by abdominal aortic ischemia-reperfusion.

Dietary α-Mangostin Provides Protective Effects against Acetaminophen-Induced Hepatotoxicity in Mice via Akt/mTOR-Mediated Inhibition of Autophagy and Apoptosis

Acetaminophen overdose-induced hepatotoxicity is the most common cause of acute liver failure in many countries. Previously, alpha-mangostin (α-MG) has been confirmed to exert protective effects on a variety of liver injuries, but the protective effect on acetaminophen-induced acute liver injury (ALI) remains largely unknown. This work investigated the regulatory effect and underlying cellular mechanisms of α-MG action to attenuate acetaminophen-induced hepatotoxicity in mice. The increased serum aminotransferase levels and glutathione (GSH) content and reduced malondialdehyde (MDA) demonstrated the protective effect of α-MG against acetaminophen-induced hepatotoxicity. In addition, α-MG pretreatment inhibited increases in tumor necrosis factor (TNF-α) and interleukin-1β (IL-1β) caused by exposure of mice to acetaminophen. In liver tissues, α-MG inhibited the protein expression of autophagy-related microtubule-associated protein light chain 3 (LC3) and BCL2/adenovirus E1B protein-interacting protein 3 (BNIP3). Western blotting analysis of liver tissues also proved evidence that α-MG partially inhibited the activation of apoptotic signaling pathways via increasing the expression of Bcl-2 and decreasing Bax and cleaved caspase 3 proteins. In addition, α-MG could in part downregulate the increase in p62 level and upregulate the decrease in p-mTOR, p-AKT and LC3 II /LC3 I ratio in autophagy signaling pathways in the mouse liver. Taken together, our findings proved novel perspectives that detoxification effect of α-MG on acetaminophen-induced ALI might be due to the alterations in Akt/mTOR pathway in the liver.

Acetaminophen attenuates lipopolysaccharide-induced cognitive impairment through antioxidant activity

Background

Considerable evidence has shown that neuroinflammation and oxidative stress play an important role in the pathophysiology of postoperative cognitive dysfunction (POCD) and other progressive neurodegenerative disorders. Increasing evidence suggests that acetaminophen (APAP) has unappreciated antioxidant and anti-inflammatory properties. However, the impact of APAP on the cognitive sequelae of inflammatory and oxidative stress is unknown. The objective of this study is to explore whether APAP could have neuroprotective effects on lipopolysaccharide (LPS)-induced cognitive impairment in mice.

Methods

A mouse model of LPS-induced cognitive impairment was established to evaluate the neuroprotective effects of APAP against LPS-induced cognitive impairment. Adult C57BL/6 mice were treated with APAP half an hour prior to intracerebroventricular microinjection of LPS and every day thereafter, until the end of the study period. The Morris water maze was used to assess cognitive function from postinjection days 1 to 3. Animal behavioural tests as well as pathological and biochemical assays were performed to evaluate LPS-induced hippocampal damage and the neuroprotective effect of APAP.

Results

Mice treated with LPS exhibited impaired performance in the Morris water maze without changing spontaneous locomotor activity, which was ameliorated by treatment with APAP. APAP suppressed the accumulation of pro-inflammatory cytokines and microglial activation induced by LPS in the hippocampus. In addition, APAP increased SOD activity, reduced MDA levels, modulated glycogen synthase kinase 3β (GSK3β) activity and elevated brain-derived neurotrophic factor (BDNF) expression in the hippocampus. Moreover, APAP significantly decreased the Bax/Bcl-2 ratio and neuron apoptosis in the hippocampus of LPS-treated mice.

Conclusions

Our results suggest that APAP may possess a neuroprotective effect against LPS-induced cognitive impairment and inflammatory and oxidative stress via mechanisms involving its antioxidant and anti-inflammatory properties, as well as its ability to inhibit the mitochondrial permeability transition (MPT) pore and the subsequent apoptotic pathway.

Effects of Senegenin against hypoxia/reoxygenation-induced injury in PC12 cells

OBJECTIVE

To investigate the effect and the potential mechanism of Senegenin (Sen) against injury induced by hypoxia/reoxygenation (H/R) in highly differentiated PC12 cells.

METHODS

The cultured PC12 cells were treated with H/R in the presence or absence of Sen (60 μmol/L). Four groups were included in the experiment: control group, H/R group, H/R+Sen group and Sen group. Cell viability of each group and the level of lactate dehydrogenase (LDH) in culture medium were detected for the pharmacological effect of Sen. Hoechst 33258 staining and annexin V/propidium iodide double staining were used to analyze the apoptosis rate. Moreover, mitochondrial membrane potential (△Ψm), reactive oxygen species (ROS) and intracellular free calcium ([Ca(2+)]i) were measured by fluorescent staining and flow cytometry. Cleaved caspase-3 and activity of NADPH oxidase (NOX) were determined by colorimetric protease assay and enzyme linked immunosorbent assay, respectively.

RESULTS

Sen significantly elevated cell viability (P<0.05), decreased the leakage of LDH (P<0.05) and apoptosis rate (P<0.05) in H/R-injured PC12 cells. Sen maintained the value of △Ψm (P<0.05) and suppressed the activity of caspase-3 (P<0.05). Moreover, Sen reduced ROS accumulation P<0.05) and [Ca(2+)]i increment (P<0.05) by inhibiting the activity of NOX (P<0.05).

CONCLUSION

Sen may exert cytoprotection against H/R injury by decreasing the levels of intracellular ROS and [Ca(2+)]i, thereby suppressing the mitochondrial pathway of cellular apoptosis.

Acetaminophen from liver to brain: New insights into drug pharmacological action and toxicity

Acetaminophen (APAP) is a well-known analgesic and antipyretic drug. It is considered to be safe when administered within its therapeutic range, but in cases of acute intoxication, hepatotoxicity can occur. APAP overdose is the leading cause of acute liver failure in the northern hemisphere. Historically, studies on APAP toxicity have been focused on liver, with alterations in brain function attributed to secondary effects of acute liver failure. However, in the last decade the pharmacological mechanism of APAP as a cannabinoid system modulator has been documented and some articles have reported "in situ" toxicity by APAP in brain tissue at high doses. Paradoxically, low doses of APAP have been reported to produce the opposite, neuroprotective effects. In this paper we present a comprehensive, up-to-date overview of hepatic toxicity as well as a thorough review of both toxic and beneficial effects of APAP in brain.

A tetramethylpyrazine piperazine derivate CXC137 prevents cell injury in SH-SY5Y cells and improves memory dysfunction of rats with vascular Dementia

We investigated the effects of CXC137, a tetramethylpyrazine piperazine derivate, on cell damage induced by N-methyl-D-aspartate (NMDA) in human derived neuroblastoma cells (SH-SY5Y) and its effect on memory dysfunction of rats with vascular dementia. It was found that the presence of CXC137 increased SH-SY5Y cells viability by inhibition of cell apoptosis induced by NMDA. These effects of CXC137 were accompanied by increases of the antioxidant superoxide dismutase activity and the level of reduced glutathione, and a decrease of lipid peroxidation product, malondialdehyde. The presence of CXC137 also showed to produce strong inhibition of cellular lactate dehydrogenase leakage, cell apoptosis and intracellular calcium overload. In a vascular dementia rat model established by bilateral common carotid arteries occlusion, treatment with CXC137 from 2 to 35 day of post-operation significantly improves the motor performance, spatial learning and memory capability of rats in both the prehensile traction test and Morris water maze test, an effect that was companied by reductions of the animal glutamic acid levels and the degree of brain mitochondrial swelling. These results suggest that CXC137 can improve the memory dysfunction in dementia and thus has important therapeutic potential for the treatment of dementia.

Use of paracetamol in ischaemic stroke patients: evidence from VISTA

OBJECTIVES

Paracetamol is frequently prescribed for pain and fever control in acute stroke patients, but its effect on stroke outcome is unclear. The aim was to investigate the safety and benefit of paracetamol administration in the acute phase of ischaemic stroke.

METHODS

We analysed the impact of paracetamol exposure on functional outcome at 90 days among ischaemic stroke patients registered in a clinical trials archive. We used an adjusted Cochran-Mantel-Haenszel test to test for significance (P) followed by proportional odds logistic regression analysis to estimate the odds ratios (OR) for more favourable modified Rankin Scale score.

RESULTS

Data were available for 6015 patients, of whom 2435 had received paracetamol. No association of paracetamol-use with overall stroke outcome could be detected among those patients who experienced pain and/or fever (OR 1.03, 95% CI 0.86-1.20, P = 0.931). In patients without recorded pain and/or fever events and a baseline temperature below 37°C, in whom paracetamol was started within 3 days of stroke, paracetamol was associated with worse outcome (OR 0.58, 95% CI 0.47-0.72, P = <0.001).

CONCLUSION

This retrospective analysis is discouraging for prophylactic use of paracetamol in acute stroke patients, but underlines the need for a sufficiently powered randomized controlled trial.

The modern pharmacology of paracetamol: therapeutic actions, mechanism of action, metabolism, toxicity and recent pharmacological findings

Paracetamol is used worldwide for its analgesic and antipyretic actions. It has a spectrum of action similar to that of NSAIDs and resembles particularly the COX-2 selective inhibitors. Paracetamol is, on average, a weaker analgesic than NSAIDs or COX-2 selective inhibitors but is often preferred because of its better tolerance. Despite the similarities to NSAIDs, the mode of action of paracetamol has been uncertain, but it is now generally accepted that it inhibits COX-1 and COX-2 through metabolism by the peroxidase function of these isoenzymes. This results in inhibition of phenoxyl radical formation from a critical tyrosine residue essential for the cyclooxygenase activity of COX-1 and COX-2 and prostaglandin (PG) synthesis. Paracetamol shows selectivity for inhibition of the synthesis of PGs and related factors when low levels of arachidonic acid and peroxides are available but conversely, it has little activity at substantial levels of arachidonic acid and peroxides. The result is that paracetamol does not suppress the severe inflammation of rheumatoid arthritis and acute gout but does inhibit the lesser inflammation resulting from extraction of teeth and is also active in a variety of inflammatory tests in experimental animals. Paracetamol often appears to have COX-2 selectivity. The apparent COX-2 selectivity of action of paracetamol is shown by its poor anti-platelet activity and good gastrointestinal tolerance. Unlike both non-selective NSAIDs and selective COX-2 inhibitors, paracetamol inhibits other peroxidase enzymes including myeloperoxidase. Inhibition of myeloperoxidase involves paracetamol oxidation and concomitant decreased formation of halogenating oxidants (e.g. hypochlorous acid, hypobromous acid) that may be associated with multiple inflammatory pathologies including atherosclerosis and rheumatic diseases. Paracetamol may, therefore, slow the development of these diseases. Paracetamol, NSAIDs and selective COX-2 inhibitors all have central and peripheral effects. As is the case with the NSAIDs, including the selective COX-2 inhibitors, the analgesic effects of paracetamol are reduced by inhibitors of many endogenous neurotransmitter systems including serotonergic, opioid and cannabinoid systems. There is considerable debate about the hepatotoxicity of therapeutic doses of paracetamol. Much of the toxicity may result from overuse of combinations of paracetamol with opioids which are widely used, particularly in USA.

PI3K/Akt Pathway Contributes to Neurovascular Unit Protection of Xiao-Xu-Ming Decoction against Focal Cerebral Ischemia and Reperfusion Injury in Rats

In the present study, we used a focal cerebral ischemia and reperfusion rat model to investigate the protective effects of Xiao-Xu-Ming decoction (XXMD) on neurovascular unit and to examine the role of PI3K (phosphatidylinositol 3-kinase)/Akt pathway in this protection. The cerebral ischemia was induced by 90 min of middle cerebral artery occlusion. Cerebral infarct area was measured by tetrazolium staining, and neurological function was observed at 24 h after reperfusion. DNA fragmentation assay, combined with immunofluorescence, was performed to evaluate apoptosis of neuron, astrocyte, and vascular endothelial cell which constitute neurovascular unit. The expression levels of proteins involved in PI3K/Akt pathway were detected by Western blot. The results showed that XXMD improved neurological function, decreased cerebral infarct area and neuronal damage, and attenuated cellular apoptosis in neurovascular unit, while these effects were abolished by inhibition of PI3K/Akt with LY294002. We also found that XXMD upregulated p-PDKl, p-Akt, and p-GSK3 β expression levels, which were partly reversed by LY294002. In addition, the increases of p-PTEN and p-c-Raf expression levels on which LY294002 had no effect were also observed in response to XXMD treatment. The data indicated the protective effects of XXMD on neurovascular unit partly through the activation of PI3K/Akt pathway.

A variety of mild stresses upregulate stanniocalcin-1 (STC-1) and induce mitohormesis in neural crest-derived cells

We induced upregulation of stanniocalcin-1 (STC-1) by various mild and long lasting stresses and assayed its influence on mitochondrial membrane potential (MMP) in the neural crest-derived cell line Paju. The obtained data showed that starvation (24-96 h), exposure to 10nM TPA, and low concentrations (0.05-1 μM) of As2O3 significantly (3-5 times) upregulated Paju cell STC-1 RNA and stabilized the mitochondrial membrane potential (MMP). However, high concentrations of As2O3 (2.5-5.0 μM) increased intracellular ROS and free calcium levels and, consequently, suppressed STC-1 and MMP. The results show that cells preconditioned by various mild stresses expressed more STC-1 and their MMP were more resistant to a secondary exposure to As2O3 (2.5-5 μM, 96 h) demonstrating mitohormesis. We suggest that MMP deviation from control levels, to an extent innocuous to cell viability, is a general signal for STC-1-induction and MMP-protection. Our findings of Paju cell MMP-regulation may be of great importance for inventing new ways to prevent neurodegenerative diseases and unravel the mechanisms behind drug resistance.

Serum caspase-9 levels are increased in patients with amyotrophic lateral sclerosis

It is known that apoptosis may play a role in the pathophysiology of amyotrophic lateral sclerosis (ALS). Moreover, caspase-9 is implicated in the apoptosis pathway. The aim of the study was to investigate caspase-9 levels in serum of patients with ALS. The study involved 30 patients with ALS and 30 patients from the control group. The serum caspase-9 levels were measured using the enzyme-linked immunosorbent method. The study showed that caspase-9 levels are significantly increased in serum of the patients with ALS comparing to the control group (p < 0.05). There was a significant correlation of serum caspase-9 levels with severity of clinical state of ALS patients and duration of the disease (p < 0.05). The results indicate that caspase-9 may be implicated in pathomechanism of neurodegeneration in ALS.

Tin chloride enhances parvalbumin-positive interneuron survival by modulating heme metabolism in a model of cerebral ischemia

SnCl(2) has been reported to increase the expression of heme-oxygenase 1 (HO-1), a major antioxidant enzyme, and to decrease ischemic injury, in non-nervous tissues. This study examined the neuroprotective effect of SnCl(2) in the hippocampus of rats submitted to cerebral ischemia. SnCl(2) was administered 18 h before bilateral carotids obstruction. Changes in HO-1 expression and activity, heme content, inducible nitric oxide synthase (iNOS) expression and parvalbumin positive interneuron survival were studied. Thereafter both behavior and memory recovery were tested. The administration of SnCl(2) increased the expression of HO-1 protein and HO activity in the hippocampus and concomitantly decreased heme content at both mitochondrial and nuclear level. Furthermore, ischemized animals showed a strong increase in iNOS expression in the hippocampus, where a loss of parvalbumin positive interneurons also occurred. Pre-treatment with SnCl(2), decreased both iNOS expression in ischemized rats and increased cell survival. The beneficial effects of SnCl(2) were prevented by concomitant treatment with SnMP, a strong inhibitor of HO activity. SnCl(2) also caused an improvement in short term memory recovery. Our results showed that following SnCl(2) administration, HO-1 is strongly induced in the hippocampus and modulate iNOS expression, resulting in a strong neuroprotective effect.

Osteopontin expression during early cerebral ischemia-reperfusion in rats: enhanced expression in the right cortex is suppressed by acetaminophen

Osteopontin (OPN) is a pleiotropic protein implicated in various inflammatory responses including ischemia-reperfusion (I-R) injury. Two distinct forms of the protein have been identified: an extensively studied secreted form (sOPN) and a less-well-known intracellular form (iOPN). Studies have shown that increased OPN expression parallels the time course of macrophage infiltration into injured tissue, a late event in the development of cerebral infarcts. sOPN has been suggested to promote remodeling of the extracellular matrix in the brain; the function of iOPN may be to facilitate certain signal transduction processes. Here, we studied OPN expression in adult male Sprague-Dawley rats subjected to global forebrain I-R injury. We found iOPN in the cytoplasm of both cortices and the hippocampus, but unexpectedly only the right cortex exhibited a marked increase in the iOPN level after 45 min of reperfusion. Acetaminophen, a drug recently shown to decrease apoptotic incidence, caspase-9 activation, and mitochondrial dysfunction during global I-R, significantly inhibited the increase in iOPN protein in the right cortex, suggesting a role for iOPN in the response to I-R injury in the right cortex.