Manganese Induces Oxidative Impairment in Cultured Rat Astrocytes

B63. Experimental Models in Pulmonary Hypertension I

et al. 2012

AimsPulmonary arterial endothelial cells (PAECs) express the enzymes needed for generation of L-arginine from intracellular L-citrulline but do not express the enzymes needed for de novo L-citrulline synthesis. Hence, L-citrulline levels in PAECs are dependent on L-citrulline transport. Once generated, L-arginine can be converted to L-citrulline and nitric oxide (NO) by the enzyme NO synthase. We sought to determine whether hypoxia, a condition aetiologically linked to pulmonary hypertension, alters the transport of L-citrulline and the expression of the sodium-coupled neutral amino acid transporters (SNATs) in PAECs from newborn piglets. Methods and resultsPAECs isolated from newborn piglets were cultured under normoxic and hypoxic conditions and used to measure SNAT1, 2, 3, and 5 protein expression and 14 C-L-citrulline uptake. SNAT1 protein expression was increased, while SNAT2, SNAT3, and SNAT5 expression was unaltered in hypoxic PAECs. 14 C-L-citrulline uptake was increased in hypoxic PAECs. Studies with inhibitors of System A (SNAT1/2) and System N (SNAT3/5) revealed that the increased 14 C-L-citrulline uptake was largely due to System A-mediated transport. Additional studies were performed to evaluate SNAT protein expression and L-citrulline levels in lungs of piglets with chronic hypoxia-induced pulmonary hypertension and comparable age controls. Lungs from piglets raised in chronic hypoxia exhibited greater SNAT1 expression and higher L-citrulline levels than lungs from controls. ConclusionIncreased SNAT1 expression and the concomitant enhanced ability to transport L-citrulline in PAECs could represent an important regulatory mechanism to counteract NO signalling impairments known to occur during the development of chronic hypoxia-induced pulmonary hypertension in newborns. ----------------------------------------------------------------------- KeywordsPulmonary hypertension † Sodium-coupled neutral amino acid transporters † Nitric oxide

Section: Figure 4 (A -D)mentioning

confidence: 58%

Prolonged Hypoxia Augments L-Citrulline Transport By System A In The Newborn Piglet Pulmonary Circulation

Fike

Sidoryk‐Węgrzynowicz

B63. Experimental Models in Pulmonary Hypertension I

et al. 2012

“…The effects of the Mn-induced release of LDH and reduction of MTT can be sustained for 24 hr, with the peak occurring between 2 and 6 hr. Our previous study demonstrated that Mn-induced oxidative stress leads to mitochondrial dysfunction in astrocytes (Milatovic et al, 2007). Other authors have also reported that Mn exerts oxidative stress and increases free radical production in experimental models of Mn neurotoxicity (Brenneman et al, 1999;HaMai and Bondy 2004).…”

Section: Discussionmentioning

confidence: 81%

“…Mitochondrial Mn-SOD uses Mn for scavenging and detoxifying free radicals. Furthermore, Mn-SOD is critical in preventing or limiting apoptotosis and necrosis resulting from cellular damage caused by reactive oxygen species (ROS) (Raha and Robinson 2000;Halliwell 2001;Kitazawa et al, 2002;Milatovic et al, 2007). Changes in Mn-containing proteins have been observed in many neurodegenerative diseases, including Alzheimer's disease, amyotrophic lateral sclerosis and Parkinsonian-like syndrome (Frankel et al, 2000;Malecki 2001;Recette et al, 2001;Zelko et al, 2002;Olanow 2004;Petrozzi et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…Our results are also in agreement with an earlier study by Rama Rao and Norenberg (2004), which found that Mn causes a dissipation of the ΔΨm in a concentration-and time-dependent manner in astrocytes. The mechanism(s) by which Mn induces the MPT in astrocytes is not completely understood; however, increased production of ROS and associated oxidative stress are generally considered major contributing factors (Castilho et al, 1995;Rama Rao and Norenberg, 2004;Milatovic et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…Mitochondria are intracellular target for Mn toxicity (Gunter et al, 2006;Milatovic et al, 2007;Rama Rao et al, 2007). Intracellular Mn 2+ is sequestered by mitochondria via the Ca 2+ uniporter (Mela and Chance, 1968;Gunter et al, 1975;Gavin et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mitochondrial-dependent manganese neurotoxicity in rat primary astrocyte cultures

Yin

Santos³

et al. 2008

Brain Research

116

Chronic exposure to excessive levels of Mn results in a movement disorder termed manganism, which resembles Parkinson's disease (PD). The pathogenic mechanisms underlying this disorder are not fully understood. Several lines of evidence implicate astrocytes as an early target of Mn neurotoxicity. In the present study, we investigated the effects of Mn on mitochondrial function. Primary astrocyte cultures were prepared from cerebral cortices of one-day-old Sprague-Dawley rats. We have examined the cellular toxicity of Mn and its effects on the phosphorylation of extracellular signalregulated kinase (ERK) and activation of the precursor protein of caspase-3. The potentiometric dye, tetramethylrhodamine ethyl ester (TMRE), was used to assess the effect of Mn on astrocytic mitochondrial inner membrane potential (ΔΨ m ). Our studies show that, in a concentration-dependent manner, Mn induces significant (p<0.05) activation of astrocyte caspase-3 and phosphorylated extracellular signal-regulated kinase (p-ERK). Mn treatment (1 and 6 hrs) also significantly (p<0.01) dissipates the ΔΨm in astrocytes as evidenced by a decrease in mitochondrial TMRE fluorescence. These results suggest that activations of astrocytic caspase-3 and ERK are involved in Mn-induced neurotoxicity via mitochondrial-dependent pathways.

Measurement of Isoprostanes as Markers of Oxidative Stress in Neuronal Tissue

Milatović

2009

CP Toxicology

Oxidative stress is implicated in the pathogenesis of a variety of human diseases, including neurodegenerative disease, atherosclerosis and cancer, as well as progressive and even normal aging processes. Increased generation of free radicals derived primarily from molecular oxygen has also been associated with neuronal damage induced by a variety of environmental agents. However, measuring oxidative stress in biological systems is complex and requires accurate quantification of either free radicals or damaged biomolecules. One method to quantify oxidative injury is to measure lipid peroxidation. Lipids are readily attacked by free radicals, resulting in the formation of a number of peroxidation products. F 2 -isoprostanes (F 2 -IsoPs) are one group of these compounds, which are derived by the free radical peroxidation of arachidonic acid (AA). The F 2 -IsoPs, prostaglandine F 2 -like compounds, have been shown as the most accurate measure of oxidative damage in vivo. This review summarizes current methodology used to quantify F 2 -IsoPs and discusses the utility of these and other prostaglandine (PG)-like compounds as in vivo biomarkers of oxidative stress in neuronal tissues.