Myoclonic involuntary movement associated with chronic manganese poisoning

Upregulation of the secretory pathway Ca2+/Mn2+-ATPase isoform 1 in LPS-stimulated microglia and its involvement in Mn2+-induced Golgi fragmentation

Microglia play an important protective role in the healthy nervous tissue, being able to react to a variety of stimuli that induce different intracellular cascades for specific tasks. Ca2+ signaling can modulate these pathways, and we recently reported that microglial functions depend on the endoplasmic reticulum as a Ca2+ store, which involves the Ca2+ transporter SERCA2b. Here, we investigated whether microglial functions may also rely on the Golgi, another intracellular Ca2+ store that depends on the secretory pathway Ca2+/Mn2+-transport ATPase isoform 1 (SPCA1). We found upregulation of SPCA1 upon lipopolysaccharide stimulation of microglia BV2 cells and primary microglia, where alterations of the Golgi ribbon were also observed. Silencing and overexpression experiments revealed that SPCA1 affects cell morphology, Golgi apparatus integrity, and phagocytic functions. Since SPCA1 is also an efficient Mn2+ transporter and considering that Mn2+ excess causes manganism in the brain, we addressed the role of microglial SPCA1 in Mn2+ toxicity. Our results revealed a clear effect of Mn2+ excess on the viability and morphology of microglia. Subcellular analysis showed Golgi fragmentation and subsequent alteration of SPCA1 distribution from early stages of toxicity. Removal of Mn2+ by washing improved the culture viability, although it did not effectively reverse Golgi fragmentation. Interestingly, pretreatment with curcumin maintained microglia cultures viable, prevented Mn2+-induced Golgi fragmentation, and preserved SPCA Ca2+-dependent activity, suggesting curcumin as a potential protective agent against Mn2+-induced Golgi alterations in microglia.

Magnetic Resonance Imaging and Manganism: A Narrative Review and Laboratory Recommendations

In recent years, a series of articles has been published concerning magnetic resonance imaging (MRI) studies in a group of patients exposed to manganism, specifically factory workers, welders, and individuals with liver diseases, as well as those abusing home-produced ephedrone. Some potential symptoms of manganese toxicity include motor disturbances, neurocognitive problems, sleep disorders, and psychosocial changes. Despite various publications on MRI research in individuals with an elevated risk of manganism, there is a noticeable absence of a comprehensive review in this field. The detection of the accumulation of manganese in the brain through MRI can confirm the diagnosis and guide appropriate treatment. Due to the high cost of determining manganese ion levels in biological material, an additional aim of the manuscript was to identify simple medical laboratory parameters that, when performed concurrently with MRI, could assist in the diagnosis of manganism. Among these types of parameters are the levels of bilirubin, magnesium, liver enzymes, creatinine, hemoglobin, and hematocrit.

Manganese and Movement Disorders: A Review

Scientific and technological advances achieved with industrial expansion have led to an ever-increasing demand for heavy metals. This demand has, in turn, led to increased contamination of soil, water and air with these metals. Chronic exposure to metals may be detrimental not only to occupational workers but also to the nonoccupational population exposed to these metals. Manganese (Mn), a commonly used heavy metal, is an essential cofactor for many enzymatic processes that drive biological functions. However, it is also a potential source of neurotoxicity, particularly in the field of movement disorders. The typical manifestation of Mn overexposure is parkinsonism, which may be difficult to differentiate from the more common idiopathic Parkinson's disease. In addition to environmental exposure to Mn, other potential etiologies causing hypermanganesemia include systemic health conditions, total parenteral nutrition and genetic mutations causing Mn dyshomeostasis. In this review, we critically analyze Mn and discuss its sources of exposure, pathophysiology and clinical manifestations. We have highlighted the global public health impact of Mn and emphasize that movement disorder specialists should record a detailed social and occupational history to ensure that a toxic etiology is not misdiagnosed as a neurodegenerative disease. In the absence of a definite therapeutic option, early diagnosis and timely institution of preventive measures are the keys to managing its toxic effects.

Ethanol exacerbates manganese-induced oxidative/nitrosative stress, pro-inflammatory cytokines, nuclear factor-κB activation, and apoptosis induction in rat cerebellar cortex

Manganese (Mn) exposure is causing public health concerns as well as heavy alcohol consumption. This study investigates the mechanisms of neurotoxicity associated with Mn and ethanol (EtOH) exposure in the rat cerebellar cortex. Experimental animals received 30 mg/kg of Mn alone, 5 g/kg of EtOH alone, co-exposed with 30 mg/kg of Mn and 1.25 or 5 g/kg EtOH, while control animals received water by oral gavage for 35 days. Subsequently, alterations in the neuronal morphology of the cerebellar cortex, oxidative/nitrosative stress, acetylcholinesterase (AChE) activity, neuro-inflammation and protein expression of p53, BAX, caspase-3, and BCL-2 were investigated. The results indicate that Mn alone and EtOH alone induce neuronal alterations in the cerebellar cortex, decrease glutathione level and antioxidant enzyme activities, along with an increase in AChE activity, lipid peroxidation, and hydrogen peroxide generation. Mn alone and EtOH alone also increased neuro-inflammatory markers, namely nitric oxide, myeloperoxidase activity, interleukin-1β, tumor necrosis factor-α, and nuclear factor-κB (NF-κB) levels in the cerebellar cortex. Immunohistochemistry analysis further revealed that exposure of Mn alone and EtOH alone increases the protein expression of cyclooxygenase-2, BAX, p53, and caspase-3 and decrease BCL-2 in the rat cerebellar cortex. Furthermore, the results indicated that Mn co-exposure with EtOH at 1.25 and 5 g/kg EtOH significantly (p ≤ .05) increases the toxicity in the cerebellum when compared with the toxicity of Mn or EtOH alone. Taken together, co-exposure of Mn and EtOH exacerbates neuronal alterations, oxidative/nitrosative stress, AChE activity, pro-inflammatory cytokines, NF-κB signal transcription, and apoptosis induction in the rat cerebellar cortex.

Manganese-induced neurodegenerative diseases and possible therapeutic approaches

INTRODUCTION

Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis and prion disease represent important public health concerns. Exposure to high levels of  heavy metals such as manganese (Mn) may contribute to their development.

AREAS COVERED

In this critical review, we address the role of Mn in the etiology of neurodegenerative diseases and discuss emerging treatments of Mn overload, such as chelation therapy. In addition, we discuss natural and synthetic compounds under development as prospective therapeutics. Moreover, bioinformatic approaches to identify new potential targets and therapeutic substances to reverse the neurodegenerative diseases are discussed.

EXPERT OPINION

Here, the authors highlight the importance of better understanding the molecular mechanisms of toxicity associated with neurodegenerative diseases, and the role of Mn in these diseases. Additional emphasis should be directed to the discovery of new agents to treat Mn-induced diseases, since present day chelator therapies have limited bioavailability. Furthermore, the authors encourage the scientific community to develop research using libraries of compounds to screen those compounds that show efficacy in regulating brain Mn levels. In addition, bioinformatics may provide novel insight for pathways and clinical treatments associated with Mn-induced neurodegeneration, leading to a new direction in Mn toxicological research.

Manganese-induced neurotoxicity and the potential protective effects of lipoic acid and Spirulina platensis

Manganese (Mn) is essential for many physiological processes; however, its excessive accumulation in the brain causes severe dysfunctions in the nervous system. Oxidative stress is thought to be involved in Mn-induced neurotoxicity. The aim of this study was to evaluate the neurotoxic effects of Mn and the potential protective effects of alpha lipoic acid (ALA) and Spirulina platensis (SP), each alone and in combination. Sixty-four male albino rats were divided into eight equal groups: group 1 was used as control, group 2 received saline, which used as a vehicle, group 3 received ALA (50 mg/kg/day), group 4 received SP (300 mg/kg/day), group 5 received Mn (74 mg/kg, 5 days/week), group 6 received Mn + ALA, group 7 received Mn + SP, group 8 received Mn + ALA + SP. Groups 6, 7 and 8 received the same previously mentioned doses. All treatments were orally gavaged for 8 weeks. Mn administration caused neurobehavioral changes, increases of brain and serum Mn and malondialdehyde (MDA), with decreased glutathione peroxidase (GPx), dopamine and acetylcholine levels. The co-treatment with ALA and SP revealed their ability to protect against oxidative damage, neurobehavioral and biochemical changes induced by Mn.

The impact of manganese on neurotransmitter systems

BACKGROUND

Manganese (Mn) is a metal ubiquitously present in nature and essential for many living organisms. As a trace element, it is required in small amounts for the proper functioning of several important enzymes, and reports of Mn deficiency are indeed rare.

METHODS

This mini-review will cover aspects of Mn toxicokinetics and its impact on brain neurotransmission, as well as its Janus-faced effects on humans and other animal's health.

RESULTS

The estimated safe upper limit of intracellular Mn for physiological function is in anarrow range of 20-53 μM.Therefore, intake of higher levels of Mn and the outcomes, especially to the nervous system, have been well documented.

CONCLUSION

The metal affects mostly the brain by accumulating in specific areas, altering cognitive functions and locomotion, thus severely impacting the health of the exposed organisms.

Iron and manganese-related CNS toxicity: mechanisms, diagnosis and treatment

INTRODUCTION

Iron (Fe) and manganese (Mn) are essential nutrients for humans. They act as cofactors for a variety of enzymes. In the central nervous system (CNS), these two metals are involved in diverse neurological activities. Dyshomeostasis may interfere with the critical enzymatic activities, hence altering the neurophysiological status and resulting in neurological diseases. Areas covered: In this review, the authors cover the molecular mechanisms of Fe/Mn-induced toxicity and neurological diseases, as well as the diagnosis and potential treatment. Given that both Fe and Mn are abundant in the earth crust, nutritional deficiency is rare. In this review the authors focus on the neurological disorders associated with Mn and Fe overload. Expert commentary: Oxidative stress and mitochondrial dysfunction are the primary molecular mechanism that mediates Fe/Mn-induced neurotoxicity. Although increased Fe or Mn concentrations have been found in brain of patients, it remains controversial whether the elevated metal amounts are the primary cause or secondary consequence of neurological diseases. Currently, treatments are far from satisfactory, although chelation therapy can significantly decrease brain Fe and Mn levels. Studies to determine the primary cause and establish the molecular mechanism of toxicity may help to adapt more comprehensive and satisfactory treatments in the future.

Neurotoxic effects of subchronic intratracheal Mn nanoparticle exposure alone and in combination with other welding fume metals in rats

Manganese (Mn) is a toxic heavy metal exposing workers in various occupational settings and causing, among others, nervous system damage. Metal fumes of welding, a typical source of Mn exposure, contain a complex mixture of metal oxides partly in nanoparticle form. As toxic effects of complex substances cannot be sufficiently understood by examining its components separately, general toxicity and functional neurotoxicity of a main pathogenic welding fume metal, Mn, was examined alone and combined with iron (Fe) and chromium (Cr), also frequently found in fumes. Oxide nanoparticles of Mn, Mn + Fe, Mn + Cr and the triple combination were applied, in aqueous suspension, to the trachea of young adult Wistar rats for 4 weeks. The decrease of body weight gain during treatment, caused by Mn, was counteracted by Fe, but not Cr. At the end of treatment, spontaneous and evoked cortical electrical activity was recorded. Mn caused a shift to higher frequencies, and lengthened evoked potential latency, which were also strongly diminished by co-application of Fe only. The interaction of the metals seen in body weight gain and cortical activity were not related to the measured blood and brain metal levels. Fe might have initiated protective, e.g. antioxidant, mechanisms with a more general effect.

Nonmotor Symptoms in Vascular and Other Secondary Parkinsonism

Vascular parkinsonism (VP) is a relatively frequent variant of secondary parkinsonism caused by ischemic or hemorrhagic lesions of basal ganglia, midbrain, or their links with frontal cortex. According to different investigations, various forms of cerebrovascular disease cause 1%-15% of parkinsonism cases. Nonmotor symptoms are frequently found in VP and may negatively influence on quality of life. However, nonmotor symptoms such as hallucinations, orthostatic hypotension, REM-sleep behavior disorder, and anosmia are rarely revealed in VP, which may be noted to another diagnosis or mixed pathology. Clinical value of nonmotor symptoms in normal pressure hydrocephalus, toxic, and drug-induced parkinsonism is also discussed.

Manganese-Enhanced Magnetic Resonance Imaging and Studies of Rat Behavior: Transient Motor Deficit in Skilled Reaching, Rears, and Activity in Rats After a Single Dose of MnCl2

Manganese-enhanced magnetic resonance imaging (MEMRI) has been suggested to be a useful tool to visualize and map behavior-relevant neural populations at large scale in freely behaving rodents. A primary concern in MEMRI applications is Mn²⁺ toxicity. Although a few studies have specifically examined toxicity on gross motor behavior, Mn²⁺ toxicity on skilled motor behavior was not explored. Thus, the objective of this study was to combine manganese as a functional contrast agent with comprehensive behavior evaluation. We evaluated Mn²⁺ effect on skilled reach-to-eat action, locomotion, and balance using a single pellet reaching task, activity cage, and cylinder test, respectively. The tests used are sensitive to the pathophysiology of many neurological and neurodegenerative disorders of the motor system. The behavioral testing was done in combination with a moderate dose of manganese. Behavior was studied before and after a single, intravenous infusion of MnCl₂ (48 mg/kg). The rats were imaged at 1, 3, 5, 7, and 14 days following infusion. The results show that MnCl₂ infusion resulted in detectable abnormalities in skilled reaching, locomotion, and balance that recovered within 3 days compared with the infusion of saline. Because some tests and behavioral measures could not detect motor abnormalities of skilled movements, comprehensive evaluation of motor behavior is critical in assessing the effects of MnCl₂. The relaxation mapping results suggest that the transport of Mn²⁺ into the brain is through the choroid plexus-cerebrospinal fluid system with the primary entry point and highest relaxation rates found in the pituitary gland. Relaxation rates in the pituitary gland correlated with measures of motor skill, suggesting that altered motor ability is related to the level of Mn circulating in the brain. Thus, combined MEMRI and behavioral studies that both achieve adequate image enhancement and are also free of motor skills deficits are difficult to achieve using a single systemic dose of MnCl₂.

Protective effect of green tea against neuro-functional alterations in rats treated with MnO2 nanoparticles

BACKGROUND

Inhalation of manganese-containing metal fumes at workplaces can cause central nervous damage including a Parkinson-like syndrome. Oxidative stress is likely to be involved in the pathomechanism, due to the presence of nano-sized metal oxide particles with high biological and chemical activity. Oxidative damage of the nervous system could be prevented or ameliorated by properly applied antioxidants, preferably natural ones such as green tea, a popular drink. The aim of this work was to see if orally applied green tea brew could diminish the functional neurotoxicity of manganese dioxide nanoparticles introduced into the airways of rats.

RESULTS

Young adult male Wistar rats were treated intratracheally for 6 weeks with a suspension of synthetic MnO₂ nanoparticles (4 mg/kg body weight), and received green tea brew (1 g leaves 200 mL^-1 water) as drinking fluid. Reduced body weight gain, indicating general toxicity of the nanoparticles, was not influenced by green tea. However, in rats receiving green tea the nervous system effects - changes in the spontaneous and evoked cortical activity and peripheral nerve action potential - were diminished.

CONCLUSION

The use of green tea as a neuroprotective functional drink seems to be a viable approach. © 2016 Society of Chemical Industry.

Manganese Toxicity Upon Overexposure: a Decade in Review

Exposure to manganese (Mn) causes clinical signs and symptoms resembling, but not identical to, Parkinson's disease. Since our last review on this subject in 2004, the past decade has been a thriving period in the history of Mn research. This report provides a comprehensive review on new knowledge gained in the Mn research field. Emerging data suggest that beyond traditionally recognized occupational manganism, Mn exposures and the ensuing toxicities occur in a variety of environmental settings, nutritional sources, contaminated foods, infant formulas, and water, soil, and air with natural or man-made contaminations. Upon fast absorption into the body via oral and inhalation exposures, Mn has a relatively short half-life in blood, yet fairly long half-lives in tissues. Recent data suggest Mn accumulates substantially in bone, with a half-life of about 8-9 years expected in human bones. Mn toxicity has been associated with dopaminergic dysfunction by recent neurochemical analyses and synchrotron X-ray fluorescent imaging studies. Evidence from humans indicates that individual factors such as age, gender, ethnicity, genetics, and pre-existing medical conditions can have profound impacts on Mn toxicities. In addition to body fluid-based biomarkers, new approaches in searching biomarkers of Mn exposure include Mn levels in toenails, non-invasive measurement of Mn in bone, and functional alteration assessments. Comments and recommendations are also provided with regard to the diagnosis of Mn intoxication and clinical intervention. Finally, several hot and promising research areas in the next decade are discussed.

Decline of General Intelligence in Children Exposed to Manganese from Mining Contamination in Puyango River Basin, Southern Ecuador

Based on ecosystem approaches to health (Ecohealth), this study sought to identify neurobehavioral disorders in children exposed to several levels of toxic metal pollution from gold mining in the Puyango River Basin, Southern Ecuador. Ninety-three children born or living in the study area participated in the study. A neurobehavioral test battery consisting of 12 tests assessing various functions of the nervous system was applied as well as a questionnaire regarding events of exposure of children's mothers to contaminants during perinatal period. Hair samples were taken from children to determine manganese concentrations. Descriptive and inferential statistics were applied in order to examine possible relationships between exposure events, hair manganese, and neurobehavioral disorders. Having controlled co-variables such as age and educational level, it was found that children with elevated levels of hair manganese (over 2 μg/g) had poor performance in the test of general intelligence (Raven's Progressive Color Matrices Scale PCM). The Ecohealth approach helped to identify that children in the lower Puyango Basin with very elevated levels of manganese in the river water (970 µg/L) are the ones who have the highest levels of hair manganese and the worst performance in the intelligence test.

Myoclonus in the critically ill: Diagnosis, management, and clinical impact

Myoclonus is the second most common involuntary non-epileptic movement in intensive care units following tremor-like gestures. Although there are several types of myoclonus, they remain underappreciated, and their diagnostic and prognostic associations are largely ignored. This review discusses clinical, electrophysiological, neuroanatomical, and neuroimaging characteristics of different types of myoclonus in critically ill adults along with their prognostic impact and treatment options. Myoclonus is characterized by a sudden, brief, and sometimes repetitive muscle contraction of body parts, or a brief and sudden cessation of tonic muscle innervation followed by a rapid recovery of tonus. Myoclonus can resemble physiologic and other pathologic involuntary movements. Neurologic injuries, anesthetics, and muscle relaxants interfere with the typical appearance of myoclonus. Identifying "real myoclonus" and determining the neuroanatomical origin are important, as treatment responses depend on the involved neuroanatomical structures. The identification of the type of myoclonus, the involved neuroanatomical structures, and the associated illnesses is essential to direct treatment. In conclusion, the combined clinical, electrophysiological, and neuroradiological examination reliably uncovers the neuroanatomical sources and the pathophysiology of myoclonus. Recognizing cortical myoclonus is critical, as it is treatable and may progress to generalized convulsive seizures or status epilepticus.

Manganese-Induced Parkinsonism and Parkinson's Disease: Shared and Distinguishable Features

Manganese (Mn) is an essential trace element necessary for physiological processes that support development, growth and neuronal function. Secondary to elevated exposure or decreased excretion, Mn accumulates in the basal ganglia region of the brain and may cause a parkinsonian-like syndrome, referred to as manganism. The present review discusses the advances made in understanding the essentiality and neurotoxicity of Mn. We review occupational Mn-induced parkinsonism and the dynamic modes of Mn transport in biological systems, as well as the detection and pharmacokinetic modeling of Mn trafficking. In addition, we review some of the shared similarities, pathologic and clinical distinctions between Mn-induced parkinsonism and Parkinson’s disease. Where possible, we review the influence of Mn toxicity on dopamine, gamma aminobutyric acid (GABA), and glutamate neurotransmitter levels and function. We conclude with a survey of the preventive and treatment strategies for manganism and idiopathic Parkinson’s disease (PD).

Neurotoxicity of metals

Metals are frequently used in industry and represent a major source of toxin exposure for workers. For this reason governmental agencies regulate the amount of metal exposure permissible for worker safety. While essential metals serve physiologic roles, metals pose significant health risks upon acute and chronic exposure to high levels. The central nervous system is particularly vulnerable to metals. The brain readily accumulates metals, which under physiologic conditions are incorporated into essential metalloproteins required for neuronal health and energy homeostasis. Severe consequences can arise from circumstances of excess essential metals or exposure to toxic nonessential metal. Herein, we discuss sources of occupational metal exposure, metal homeostasis in the human body, susceptibility of the nervous system to metals, detoxification, detection of metals in biologic samples, and chelation therapeutic strategies. The neurologic pathology and physiology following aluminum, arsenic, lead, manganese, mercury, and trimethyltin exposures are highlighted as classic examples of metal-induced neurotoxicity.

Roles of P-glycoprotein and multidrug resistance protein in transporting para-aminosalicylic acid and its N-acetylated metabolite in mice brain

AIM

Para-aminosalicylic acid (PAS) is effective in the treatment of manganism-induced neurotoxicity (manganism). In this study we investigated the roles of P-glycoprotein (MDR1a) and multidrug resistance protein (MRP) in transporting PAS and its N-acetylated metabolite AcPAS through blood-brain barrier.

METHODS

MDR1a-null or wild-type mice were intravenously injected with PAS (200 mg/kg). Thirty minutes after the injection, blood samples and brains were collected, and the concentrations of PAS and AcPAS in brain capillaries and parenchyma were measured using HPLC. Both MDCK-MDR1 and MDCK-MRP1 cells that overexpressed P-gp and MRP1, respectively, were used in two-chamber Transwell transport studies in vitro.

RESULTS

After injection of PAS, the brain concentration of PAS was substantially higher in MDR1a-null mice than in wild-type mice, but the brain concentration of AcPAS had no significant difference between MDR1a-null mice and wild-type mice. Concomitant injection of PAS with the MRP-specific inhibitor MK-571 (50 mg/kg) further increased the brain concentration of PAS in MDR1a-null mice, and increased the brain concentration of AcPAS in both MDR1a-null mice and wild-type mice. Two-chamber Transwell studies with MDCK-MDR1 cells demonstrated that PAS was not only a substrate but also a competitive inhibitor of P-gp, while AcPAS was not a substrate of P-gp. Two-chamber Transwell studies with the MDCK-MRP1 cells showed that MRP1 had the ability to transport both PAS and AcPAS across the BBB.

CONCLUSION

P-gp plays a major role in the efflux of PAS from brain parenchyma into blood in mice, while MRP1 is involved in both PAS and AcPAS transport in the brain.

Human health risk assessment of dissolved metals in groundwater and surface waters in the Melen watershed, Turkey

Determination of metal risk levels in potable water and their effects on human health are vital in assessment of water resources. Risk assessment of metals to human health in a watershed, which has not been studied before, is the main objective of the present study. Surface and groundwater sampling was carried out between September 2010 and August 2011 in the Melen Watershed, Turkey, an important drinking water resource for millions of people. Metals were analyzed in the laboratory using inductively coupled plasma. Of the 26 different metals monitored, Al, B, Ba, Cr, Cu, Fe, Mn, Mo and V were found in surface water and As, B, Ba, Cr, Cu, Mn, Mo, V and Zn in groundwater. In groundwater, unitless hazard quotient (HQ) values were 6 for As, 2.7 for Mn and 1 for Zn, while in surface water all metals were below the risk level (HQ < 1). The ingestion risk was found to be higher than the dermal uptake risk. Arsenic mean concentration was observed to be 0.044 mg/L in groundwater. The As carcinogenic risk (CR) value was higher than the internationally accepted risk level (10(-4)) and with maximum ingestion of groundwater the carcinogenic risk was found to be higher in adults than children. These results show that even unpolluted watersheds can pose a risk to human health and that potential carcinogenic impacts should receive more attention.

Manganese in health and disease

Manganese is an important metal for human health, being absolutely necessary for development, metabolism, and the antioxidant system. Nevertheless, excessive exposure or intake may lead to a condition known as manganism, a neurodegenerative disorder that causes dopaminergic neuronal death and parkinsonian-like symptoms. Hence, Mn has a paradoxal effect in animals, a Janus-faced metal. Extensive work has been carried out to understand Mn-induced neurotoxicity and to find an effective treatment. This review focuses on the requirement for Mn in human health as well as the diseases associated with excessive exposure to this metal.

High levels of Mn²⁺ inhibit secretory pathway Ca²⁺/Mn²⁺-ATPase (SPCA) activity and cause Golgi fragmentation in neurons and glia

Excess Mn(2+) in humans causes a neurological disorder known as manganism, which shares symptoms with Parkinson's disease. However, the cellular mechanisms underlying Mn(2+) -neurotoxicity and the involvement of Mn(2+) -transporters in cellular homeostasis and repair are poorly understood and require further investigation. In this work, we have analyzed the effect of Mn(2+) on neurons and glia from mice in primary cultures. Mn(2+) overload compromised survival of both cell types, specifically affecting cellular integrity and Golgi organization, where the secretory pathway Ca(2+) /Mn(2+) -ATPase is localized. This ATP-driven Mn(2+) transporter might take part in Mn(2+) accumulation/detoxification at low loads of Mn(2+) , but its ATPase activity is inhibited at high concentration of Mn(2+) . Glial cells appear to be significantly more resistant to this toxicity than neurons and their presence in cocultures provided some protection to neurons against degeneration induced by Mn(2+) . Interestingly, the Mn(2+) toxicity was partially reversed upon Mn(2+) removal by wash out or by the addition of EDTA as a chelating agent, in particular in glial cells. These studies provide data on Mn(2+) neurotoxicity and may contribute to explore new therapeutic approaches for reducing Mn(2+) poisoning.

Welding and parkinsonism

Manganese-induced parkinsonism has been recognized since 1837. It has been reported primarily in miners, grinders, and smelters since that time. More recently, isolated case reports involving welders have appeared in the medical literature. Manganism can be distinguished from other forms of parkinsonism by clinical presentation with support from laboratory and radiologic findings. The controversy regarding the risk of parkinsonism in welders is reviewed.

Brain regional pharmacokinetics of p-aminosalicylic acid and its N-acetylated metabolite: effectiveness in chelating brain manganese

para-aminosalicylic acid (PAS; 4-amino-2-hydroxybenzoic acid), an antituberculosis drug in use since the 1950s, has recently been suggested to be an effective agent for treatment of manganese-induced parkinsonian disorders. However, the neuropharmacokinetics of PAS and its metabolite N-acetyl-para-aminosalicylic acid (AcPAS; N-acetyl-4-amino-2-hydroxybenzoic acid) are unknown. This study was designed to investigate the pharmacokinetics of PAS and its distribution in brain to help better design the dosing regimen for clinical trials. Male Sprague-Dawley rats received single femoral artery injections of PAS (200 mg/kg). Plasma, cerebrospinal fluid, and brain tissues were collected, and PAS and AcPAS concentrations were quantified by high-performance liquid chromatography. After administration, the concentrations of PAS declined rapidly in plasma with an elimination t(½) of 34 min; the metabolite AcPAS was detected in plasma and eliminated with a t(½) of 147 min. PAS and AcPAS were detected in brain tissues; AcPAS had a much higher tissue concentration and a longer t(½) than the parent PAS in most tissues examined. Although both were present in blood or tissues as free, unbound molecules, AcPAS appeared to have a higher tissue affinity than PAS. Taken together, our results suggest that a dosing regimen with continuous intravenous infusion of PAS is necessary to achieve therapeutic levels in targeted brain regions. Furthermore, PAS and AcPAS seem to be effective in reducing manganese levels in brain.

Manganese toxicity in a child with iron deficiency and polycythemia

A previously healthy 5-year-old girl presented with pica, emotional lability, and marked gait abnormalities. She had concurrent severe iron deficiency and polycythemia. Her magnetic resonance imaging (MRI) scan showed increased signal in the basal ganglia on T1-weighted images consistent with manganese neurotoxicity. Manganism was subsequently confirmed as her blood manganese levels were extremely elevated. Chelation therapy resulted in improvement in her mobility but she continues to have significant gait impairment. An epidemiological investigation identified well water as the potential source of manganese exposure for our patient, but to date, we have been unable to identify the nature of her neurotoxic susceptibility.

Gender and manganese exposure interactions on mouse striatal neuron morphology

Gender differences in sensitivity and toxicokinetics of multiple metals have been identified in humans. A recent study suggested that young girls performed worse on intellectual exams than young boys exposed to manganese (Mn) in the environment. Animal studies have shown that Mn exposure causes differential effects on behavior in male compared to female mice. We hypothesized that in response to Mn exposure striatal Mn accumulation and/or striatal medium spiny neuron (MSN) morphology show gender-dependent effects. We evaluated the contribution of gender to neuropathology by examining striatal MSN morphology in male and female mice exposed to Mn. We found that gender played a significant role in alterations of striatal MSN morphology in mice exposed to Mn. Gender-dependent changes were strongest when striatal Mn levels were elevated 24h following the final Mn exposure. Nevertheless, gender-dependent alterations in neuron morphology were still present 3 weeks after the final Mn exposure. Gender differences in neuron morphology were not due to differential striatal Mn accumulation between genders. We conclude that although gender does not affect striatal Mn accumulation, MSN morphology is differentially sensitive to elevated Mn levels.

HPLC analysis of para-aminosalicylic acid and its metabolite in plasma, cerebrospinal fluid and brain tissues

Para-aminosalicylic acid (PAS), an approved drug for treatment of tuberculosis, is a promising therapeutic agent for treatment of manganese (Mn)-induced parkinsonian syndromes. Lack of a quantifying method, however, has hindered the clinical evaluation of its efficacy and there upon new drug development. This study was aimed at developing a simple and effective method to quantify PAS and its major metabolite, N-acetyl-para-aminosalicylic acid (AcPAS), in plasma, cerebrospinal fluid (CSF) and tissues. Biological samples underwent one-step protein precipitation. The supernatant was fractionated on a reversed-phase C18 column with a gradient mobile system, followed by on-line fluorescence detection. The lower limits of quantification for both PAS and AcPAS were 50 ng/ml of plasma and 17 ng/g of tissues. The intra-day and inter-day precision values did not exceed 5% and 8%, respectively, in all three matrices. The method was used to quantify PAS and AcPAS in rat plasma and brain following a single iv injection of PAS. Data showed a greater amount of PAS than AcPAS in plasma, while a greater amount of AcPAS than PAS was found in brain tissues. The method has been proven to be sensitive, reproducible, and practically useful for laboratory and clinical investigations of PAS in treatment of Mn Parkinsonism.

Biomarkers of manganese intoxication

Manganese (Mn), upon absorption, is primarily sequestered in tissue and intracellular compartments. For this reason, blood Mn concentration does not always accurately reflect Mn concentration in the targeted tissue, particularly in the brain. The discrepancy between Mn concentrations in tissue or intracellular components means that blood Mn is a poor biomarker of Mn exposure or toxicity under many conditions and that other biomarkers must be established. For group comparisons of active workers, blood Mn has some utility for distinguishing exposed from unexposed subjects, although the large variability in mean values renders it insensitive for discriminating one individual from the rest of the study population. Mn exposure is known to alter iron (Fe) homeostasis. The Mn/Fe ratio (MIR) in plasma or erythrocytes reflects not only steady-state concentrations of Mn or Fe in tested individuals, but also a biological response (altered Fe homeostasis) to Mn exposure. Recent human studies support the potential value for using MIR to distinguish individuals with Mn exposure. Additionally, magnetic resonance imaging (MRI), in combination with noninvasive assessment of γ-aminobutyric acid (GABA) by magnetic resonance spectroscopy (MRS), provides convincing evidence of Mn exposure, even without clinical symptoms of Mn intoxication. For subjects with long-term, low-dose Mn exposure or for those exposed in the past but not the present, neither blood Mn nor MRI provides a confident distinction for Mn exposure or intoxication. While plasma or erythrocyte MIR is more likely a sensitive measure, the cut-off values for MIR among the general population need to be further tested and established. Considering the large accumulation of Mn in bone, developing an X-ray fluorescence spectroscopy or neutron-based spectroscopy method may create yet another novel non-invasive tool for assessing Mn exposure and toxicity.

Effects of p-Aminosalicylic acid on the neurotoxicity of manganese on the dopaminergic innervation of the cilia of the lateral cells of the gill of the bivalve mollusc, Crassostrea virginica

The lateral cilia of the gill of Crassostrea virginica are controlled by a dopaminergic-serotonergic innervation. Dopamine is the neurotransmitter causing cilio-inhibition. High levels of manganese are neurotoxic to people, causing Manganism, a Parkinson-like disease. Clinical interventions for Manganism have not been very successful. Recently, p-Aminosalicylic acid (PAS) was reported as an effective treatment of severe Manganism in humans; however, its mechanism of action is unknown. Previously, we reported that manganese treatments caused disruption of the dopaminergic innervation of gill of C. virginica. Here we compared the effects of manganese on gill innervation in the presence of PAS, EDTA or Acetylsalicylic acid (ASA), and examined whether co-treating animals with PAS could block the deleterious effects of manganese on the oyster's dopaminergic innervation of the gill. Beating rates of the lateral cilia of the gill were measured by stroboscopic microscopy. Pre-treating gill preparations with PAS or EDTA blocked the neurotoxic effects of manganese, while ASA did not. In other experiments, animals exposed to three day treatments with manganese produced a dose dependent impairment of the dopaminergic, cilio-inhibitory system, which was decreased by co-treatment with PAS. The study shows that PAS protects the animal against neurotoxic effects of manganese and the mechanism of action of PAS in alleviating Manganism is more likely related to its chelating abilities than its anti-inflammatory actions.

Neurological risks associated with manganese exposure from welding operations--a literature review

Exposure to manganese dusts and fumes may cause a clinical neurological syndrome called manganism. Welders are frequently exposed to manganese-containing fumes generated by electric arcs and thermal torches. This paper reviews studies on the association between exposure to such welding fumes and neurological disease. Using the IRSST expert panel criteria, 78 cases of probable/possible, and 19 additional cases of possible occupational manganism were identified in the literature among manganese-exposed workers involved in welding processes. Epidemiological evidence linking welding exposures to Parkinson's disease is still controversial. Although more research is needed to clarify the risks of neurological impairment from welding, control measures including ventilation and adequate respiratory protection, should be implemented to minimize welding fume exposures. The significance of fume transport into the central nervous system via the olfactory nerve, which by-passes the blood-brain barrier, also needs to be assessed.

Manganese and its role in Parkinson's disease: from transport to neuropathology

The purpose of this review is to highlight recent advances in the neuropathology associated with Mn exposures. We commence with a discussion on occupational manganism and clinical aspects of the disorder. This is followed by novel considerations on Mn transport (see also chapter by Yokel, this volume), advancing new hypotheses on the involvement of several transporters in Mn entry into the brain. This is followed by a brief description of the effects of Mn on neurotransmitter systems that are putative modulators of dopamine (DA) biology (the primary target of Mn neurotoxicity), as well as its effects on mitochondrial dysfunction and disruption of cellular energy metabolism. Next, we discuss inflammatory activation of glia in neuronal injury and how disruption of synaptic transmission and glial-neuronal communication may serve as underlying mechanisms of Mn-induced neurodegeneration commensurate with the cross-talk between glia and neurons. We conclude with a discussion on therapeutic aspects of Mn exposure. Emphasis is directed at treatment modalities and the utility of chelators in attenuating the neurodegenerative sequelae of exposure to Mn. For additional reading on several topics inherent to this review as well as others, the reader may wish to consult Aschner and Dorman (Toxicological Review 25:147-154, 2007) and Bowman et al. (Metals and neurodegeneration, 2009).

Chelation therapy of manganese intoxication with para-aminosalicylic acid (PAS) in Sprague-Dawley rats

Para-aminosalicylic acid (PAS), an FDA-approved anti-tuberculosis drug, has been used successfully in the treatment of severe manganese (Mn)-induced Parkinsonism in humans [Jiang Y-M, Mo X-A, Du FQ, Fu X, Zhu X-Y, Gao H-Y, et al. Effective treatment of manganese-induced occupational Parkinsonism with p-aminosalicylic acid: a case of 17-year follow-up study. J Occup Environ Med 2006;48:644-9]. This study was conducted to explore the capability of PAS in reducing Mn concentrations in body fluids and tissues of Mn-exposed animals. Sprague-Dawley rats received daily intraperitoneally (i.p.) injections of 6mg Mn/kg, 5 days/week for 4 weeks, followed by a daily subcutaneously (s.c.) dose of PAS (100 and 200mg/kg as the PAS-L and PAS-H group, respectively) for another 2, 3 or 6 weeks. Mn exposure significantly increased the concentrations of Mn in plasma, red blood cells (RBC), cerebrospinal fluid (CSF), brain and soft tissues. Following PAS-H treatment for 3 weeks, Mn levels in liver, heart, spleen and pancreas were significantly reduced by 25-33%, while 3 weeks of PAS-L treatment did not show any effect. Further therapy with PAS-H for 6 weeks reduced Mn levels in striatum, thalamus, choroid plexus, hippocampus and frontal cortex by 16-29% (p<0.05). Mn exposure greatly increased iron (Fe) and copper (Cu) concentrations in CSF, brain and liver. Treatment with PAS-H restored Fe and Cu levels comparable with control. These data suggest that PAS likely acts as a chelating agent to mobilize and remove tissue Mn. A high-dose and prolonged PAS treatment appears necessary for its therapeutic effectiveness.

Brain magnetic resonance imaging (MRI) in parkinsonian disorders

Magnetic resonance imaging (MRI) is increasingly integrated into neurological diagnostics. In addition to functional MRI, a large number of sequences (T1W, T2W, PD, T2W gradient echo, diffusion-weighted imaging (DWI), and diffusion tensor imaging (DTI)), investigate CNS abnormalities. Objective quantification techniques (T1W voxel-based morphometry) can also discern subtle anatomical differences. Parkinsonian conditions such as Parkinson's disease, multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration and manganese-induced parkinsonism can clinically overlap, yet have very different prognoses and treatments. Relatively little radiographic interest has focused on movement disorders. Nevertheless in the past decade, a variety of findings, often subtle and routinely overlooked, have emerged to help the clinician differentiate these conditions. This review will summarize and discuss MRI findings in parkinsonian conditions. Most data concern either structural abnormalities or the imaging sequelae of abnormal iron deposition, common in some parkinsonian conditions.

Contamination of drinking water resources in the Mekong delta floodplains: arsenic and other trace metals pose serious health risks to population

This study presents a transnational groundwater survey of the 62,000 km(2) Mekong delta floodplain (Southern Vietnam and bordering Cambodia) and assesses human health risks associated with elevated concentrations of dissolved toxic elements. The lower Mekong delta generally features saline groundwater. However, where groundwater salinity is <1 g L(-)(1) Total Dissolved Solids (TDS), the rural population started exploiting shallow groundwater as drinking water in replacement of microbially contaminated surface water. In groundwater used as drinking water, arsenic concentrations ranged from 0.1-1340 microg L(-)(1), with 37% of the studied wells exceeding the WHO guidelines of 10 microg L(-)(1) arsenic. In addition, 50% exceeded the manganese WHO guideline of 0.4 mg L(-)(1), with concentrations being particularly high in Vietnam (range 1.0-34 mg L(-)(1)). Other elements of (minor) concern are Ba, Cd, Ni, Se, Pb and U. Our measurements imply that groundwater contamination is of geogenic origin and caused by natural anoxic conditions in the aquifers. Chronic arsenic poisoning is the most serious health risk for the ~2 million people drinking this groundwater without treatment, followed by malfunction in children's development through excessive manganese uptake. Government agencies, water specialists and scientists must get aware of the serious situation. Mitigation measures are urgently needed to protect the unaware people from such health problems.

State-of-the-science review: Does manganese exposure during welding pose a neurological risk?

Recent studies report that exposure to manganese (Mn), an essential component of welding electrodes and some steels, results in neurotoxicity and/or Parkinson's disease (PD) in welders. This "state-of-the-science" review presents a critical analysis of the published studies that were conducted on a variety of Mn-exposed occupational cohorts during the last 100 yr, as well as the regulatory history of Mn and welding fumes. Welders often perform a variety of different tasks with varying degrees of duration and ventilation, and hence, to accurately assess Mn exposures that occurred in occupational settings, some specific information on the historical work patterns of welders is desirable. This review includes a discussion of the types of exposures that occur during the welding process--for which limited information relating airborne Mn levels with specific welding activities exists--and the human health studies evaluating neurological effects in welders and other Mn-exposed cohorts, including miners, millers, and battery workers. Findings and implications of studies specifically conducted to evaluate neurobehavioral effects and the prevalence of PD in welders are also discussed. Existing exposure data indicate that, in general, Mn exposures in welders are less than those associated with the reports of clinical neurotoxicity (e.g., "manganism") in miners and smelter workers. It was also found that although manganism was observed in highly exposed workers, the scant exposure-response data available for welders do not support a conclusion that welding is associated with clinical neurotoxicity. The available data might support the development of reasonable "worst-case" exposure estimates for most welding activities, and suggest that exposure simulation studies would significantly refine such estimates. Our review ends with a discussion of the data gaps and areas for future research.

A preliminary study revealing a new association in patients undergoing maintenance hemodialysis: manganism symptoms and T1 hyperintense changes in the basal ganglia

BACKGROUND AND PURPOSE

Patients undergoing parenteral nutrition and those with portosystemic encephalopathy secondary to chronic liver disease and acquired and congenital portosystemic venous shunts frequently present manganese deposition in the basal ganglia, detected by MR imaging as hyperintense areas on T1-weighted sequences. We also observed similar abnormalities in the basal ganglia of patients with chronic renal failure undergoing maintenance hemodialysis. Our aim was to evaluate the pallidal signal intensity on T1-weighted images in a series of patients undergoing hemodialysis, with further evaluation of serum manganese levels and neurologic correlation, comparing them with patients with chronic renal failure without dialytic treatment.

MATERIALS AND METHODS

We performed MR imaging examinations in 9 patients with chronic renal failure, 5 of whom were undergoing hemodialysis. An experienced neuroradiologist scrutinized the presence of symmetric hyperintensities in the basal ganglia on T1-weighted sequences. We also determined the serum manganese levels and performed the neurologic evaluations in all patients.

RESULTS

All patients undergoing hemodialysis presented elevated serum manganese levels and symmetric hyperintensities within the globus pallidus. In this group, 4 patients presented with parkinsonian symptoms, myoclonus, and syndromes with vestibular and vestibular-auditory symptoms. The patients without dialytic treatment presented with neither bilaterally increased T1 MR imaging signal intensity within the globus pallidus nor symptoms of manganism.

CONCLUSION

Our preliminary results demonstrated the occurrence of bilateral pallidal hyperintensity on T1-weighted images in all patients undergoing hemodialysis associated with high serum manganese levels, revealing a new association.

Manganese accumulation in the brain: MR imaging

Manganese (Mn) accumulation in the brain is detected as symmetrical high signal intensity in the globus pallidi on T1-weighted MR images without an abnormal signal on T2-weighted images. In this review, we present several cases of Mn accumulation in the brain due to acquired or congenital diseases of the abdomen including hepatic cirrhosis with a portosystemic shunt, congenital biliary atresia, primary biliary cirrhosis, congenital intrahepatic portosystemic shunt without liver dysfunction, Rendu-Osler-Weber syndrome with a diffuse intrahepatic portosystemic shunt, and patent ductus venosus. Other causes of Mn accumulation in the brain are Mn overload from total parenteral nutrition and welding-related Mn intoxication.

Manganese: recent advances in understanding its transport and neurotoxicity

The present review is based on presentations from the meeting of the Society of Toxicology in San Diego, CA (March 2006). It addresses recent developments in the understanding of the transport of manganese (Mn) into the central nervous system (CNS), as well as brain imaging and neurocognitive studies in non-human primates aimed at improving our understanding of the mechanisms of Mn neurotoxicity. Finally, we discuss potential therapeutic modalities for treating Mn intoxication in humans.

Progressive motor syndrome in a welder with pallidal T1 hyperintensity on MRI: A two-year follow-up

Chronic exposure to manganese (Mn) fume during welding may lead to mainly extrapyramidal syndrome that is resistant to treatment. We present a 32-year-old patient who developed severe postural instability, Parkinsonism, dystonia, and pyramidal signs in the 10th year of welding. The neurological condition of the patient worsened markedly in the following 3 years, resulting in severe disability rendering him to be assisted in all his daily activities and he did not benefit from any dopaminergic agent. T1 sequences of the MRI of the brain showed pallidal hyperintensity symmetrically. Welders in our country often protect their eyes but ignore to use tools that protect them from inhalation of the fume. Since chronic Mn toxicity may cause serious disability and irreversible neurological disturbances, we strongly believe that it is necessary to inform welders and their employers about this potential hazard.

Effective treatment of manganese-induced occupational Parkinsonism with p-aminosalicylic acid: a case of 17-year follow-up study

OBJECTIVE

Chronic manganese (Mn) intoxication induces syndromes resembling Parkinson disease. The clinical intervention has largely been unsuccessful. We report a 17-year follow-up study of effective treatment of occupational Mn parkinsonism with sodium para-aminosalicylic acid (PAS).

METHODS

The patient, female and aged 50 at the time of treatment, was exposed to airborne Mn for 21 years (1963-1984). The patient had palpitations, hand tremor, lower limb myalgia, hypermyotonia, and a distinct festinating gait. She received 6 g PAS per day through an intravenous drip infusion for 4 days and rested for 3 days as one therapeutic course. Fifteen such courses were carried out between March and June 1987.

RESULTS

At the end of PAS treatment, her symptoms were significantly alleviated, and handwriting recovered to normal. Recent follow-up examination at age 67 years (in 2004) showed a general normal presentation in clinical, neurologic, brain magnetic resonance imaging, and handwriting examinations with a minor yet passable gait.

CONCLUSIONS

This case study suggests that PAS appears to be an effective drug for treatment of severe chronic Mn poisoning with a promising prognosis.

Is electric arc welding linked to manganism or Parkinson's disease?

Manganese and its inorganic compounds are widely used in many industries and have been accepted as occupational neurotoxins that have caused a distinct and disabling clinical entity, manganism, in several types of work, notably where exposure is by way of dust. There is inconclusive and inconsistent evidence that, in these occupations, subclinical neurological effects, detectable only by neurobehavioural studies, may be caused by low doses. This has prompted a re-evaluation of occupational exposure limits. Some countries, including the UK, already demand much higher levels of protection against exposure than 5 years ago. Welding is the most common source of occupational exposure as manganese is an essential component of steel and so its compounds are inevitable components of fume emitted from steel welding processes. There it is found in respirable particles, often as complex oxides (spinels), sometimes within a core protected by a silicon oxide shell - as distinct from the much simpler form of particle formed by disintegration in processes such as mining and ore milling where manganism has been diagnosed convincingly. Millions of workers are at risk of exposure to manganese-containing compounds in fumes from electric arc welding of steel. In recent years it has been asserted that neurological and neurobehavioural disorders may develop consequent to exposure to steel welding fumes and that employment as a welder is associated with the unusually early onset of Parkinson's disease. Causal relationships have been postulated. Welders have been recorded as having been exposed to high levels of manganese-containing fume, especially where they have worked in confined, unventilated spaces, although this appears from limited data to be the exception rather than the rule. Even then the dose received is generally less than in mining or ore crushing. When care is taken to exclude exposures from hardfacing and burning and cutting arc processes, where manganese may form a high percentage of the fume, manganese compounds usually form a relatively low percentage of the composition of welding fume particles, <2.0%, much outweighed by iron. Although these manganese-compound-containing welding fume particles are insoluble in water, the manganese compounds in particles that are retained in the alveoli may be absorbed, at least in part. Manganese concentrations in biological material samples in some exposed groups reflect this relative to unexposed workers. Some of the transfer systems for absorption and transport, including across the blood-brain barrier, are used in competition with iron which is present in abundance in welding fume. This may reduce absorption of manganese in welders and thus reduce the opportunity for sufficient doses to cause neurotoxicological consequences. Scrutiny of the literature covering the last 40 years has revealed only five cases that meet sufficient criteria for manganism to just cross the diagnostic threshold, and even then they carry a degree of doubt with them. This low incidence alone gives notice that welders have not been and are not at high risk of clinically apparent damage from exposure to manganese. If this needs to be further emphasised, there is the fact that the literature contains no confirmed cases of manganism in welders. Assertions of abnormal results in neurobehavioural studies of welders have raised the possibility of there being a subclinical form of manganism with loss of fine motor control as one of its features. While observations of such changes in workers in other industries have caused regulators in some countries to apply more stringent controls of exposure, as yet the results lack convincing consistency and there is no indication of any dose-effect relationship. If welding fume can have these motor effects it would be a heavy and perhaps career-ending blow to those affected. It would not be prudent to dismiss the warnings sounded by the results of studies of welders, no matter how flawed these investigations are, but wiser and better to act with vigour to reduce exposure and monitor the effectiveness of this additional protection whilst conducting high quality research to allow sound conclusions to be drawn as to whether there actually is a subclinical disorder. Idiopathic Parkinson's disease is a common disorder affecting 1-2% of those in the general population aged >65 years. It has been suggested, on flawed and contested evidence, not that welding causes the disease but rather that employment as a welder carries with it the risk of developing this disease at a younger age than if that trade had not been followed. Manganese in welding fume has been nominated as the neurotoxin. This may be biologically feasible if manganese destroys insufficient receptor cells to produce clinical manganism but sufficient to enhance the effects of a reduced supply of dopamine to give the manifestations of already developing idiopathic Parkinson's disease earlier in the course of destruction of the substantia nigra than if all receptors were intact.

Brain magnetic resonance imaging and manganese concentrations in red blood cells of smelting workers: search for biomarkers of manganese exposure

The MRI technique has been used in diagnosis of manganism in humans and non-human primates. This cross-sectional study was designed to explore whether the pallidal signal intensity in T1-weighted MRI correlated with Mn levels in the blood compartment among Mn-exposed workers and to understand to what extent the MRI signal could reflect Mn exposure. A group of 18 randomly selected male Mn-exposed workers of which 13 were smelting workers with high exposure (mean of airborne Mn in work place: 1.26 mg/m3; range: 0.31-2.93 mg/m3), and 5 power distribution control workers with low exposure (0.66 mg/m3 and 0.23-0.77 mg/m3) from a ferroalloy factory, and another group of 9 male subjects as controls from a non-smelting factory who were office or cafeteria workers (0.01 mg/m3 and 0-0.03 mg/m3) were recruited for neurological tests, MRI examination, and analysis of Mn in whole blood (MnB), plasma (MnP) or red blood cells (MnRBC). No clinical symptoms and signs of manganism were observed among these workers. MRI data showed average increases of 7.4% (p<0.05) and 16.1% (p<0.01) in pallidal index (PI) among low- and high-exposed workers, respectively, as compared to controls. Fourteen out of 18 Mn-exposed workers (78%) had intensified PI values, while this proportion was even higher (85%) among the high Mn-exposed workers. Among exposed workers, the PI values were significantly associated with MnRBC (r=0.55, p=0.02). Our data suggest that the workers exposed to airborne Mn, but without clinical symptoms, display an exposure-related, intensified MRI signal. The MRI, as well as MnRBC, may be useful in early diagnosis of Mn exposure.

The use of magnetic resonance imaging (MRI) in the study of manganese neurotoxicity

Manganese (Mn), an element found in many foods, is an important and essential nutrient for proper health and maintenance. It is toxic in high doses, however, and exposure to excessive levels can result in the onset of a neurological disorder similar to, but distinct from, Parkinson's disease. Historically, Mn neurotoxicity was most commonly associated with various occupations, such as Mn mining, welding and steel production. More recently, increases in both blood and brain Mn levels have been observed in persons with liver disease or those receiving prolonged parenteral nutrition. Additionally, rodent data suggest that iron deficiency and anemia may be risk factors for Mn neurotoxicity. Clinically, brain Mn accumulation can be monitored in vivo using non-invasive magnetic resonance imaging (MRI) due to the paramagnetic nature of this element. Indeed, MRI has been used in a variety of settings to evaluate the brain Mn deposition in various populations. This review focuses on the use of MRI technology in studies related specifically to Mn neurotoxicity. Thus, we will examine reports using MRI to confirm brain Mn accumulation in human populations, and conclude with data from non-human primate and rodent models of Mn neurotoxicity.

Follow-up of patients affected by manganese-induced Parkinsonism after treatment with CaNa2EDTA

In the period of 1998-2004, seven workers affected by manganese-induced Parkinsonism were diagnosed, studied and treated with CaNa2EDTA at our Occupational Health Ward. Biological markers, as well as magnetic resonance imaging and clinical examinations, were used to assess the disease trend. Those workers still employed were immediately removed from exposure. Our results seem to confirm that very good clinical, biological and neuroradiological results can be obtained by timely removal from exposure and chelating treatment, and that amelioration can persist in time. Manganism is, however, a severe condition that can also progress independent of further exposure. Therefore, chelating treatment can be a great aid in overt manganism, but particular attention must be paid to primary prevention, as this disease should now be totally preventable and definitely merits eradication.

Searching for a relationship between manganese and welding and Parkinson's disease

Research into the causes of Parkinson disease (PD) has accelerated recently with the discovery of novel gene mutations. The majority of PD cases, however, remain idiopathic and in those cases environmental causes should be considered. Several recent reports have focused on welding and manganese toxicity as potential risk factors for parkinsonism and some have even proposed that welding is a risk factor for PD. The controversy has stimulated this review, the primary aim of which is to critically and objectively examine the evidence or lack of evidence for a relationship among welding, manganese, parkinsonism, and PD.