Arsenic exposure and pruritus: Evidence from observational, interventional, and mendelian randomization studies

BACKGROUND

Pruritus is identified as an adverse drug reaction to arsenic trioxide, but the association of arsenic exposure with pruritus has not been investigated.

METHODS

A cross-sectional study was conducted in Shimen, China. A Mendelian randomization analysis was conducted to confirm the causal relationship between genetically predicted percentages of monomethylated arsenic (MMA%) and dimethylated arsenic (DMA%) in urine with chronic pruritus in UK Biobank. A case-control study was then conducted to determine the biomarker for pruritus. Arsenite-treated mice were used to confirm the biomarker, and von Frey test was used to induce scratching bouts. Last, a randomized, double-blind, placebo-controlled trial was conducted to test the efficacy of naloxone in arsenic-exposed patients with pruritus in Shimen.

RESULTS

Hair arsenic (μg/g) showed a dose-response relationship with the intensity of itch in 1079 participants, with odds ratios (OR) of 1.11 for moderate-to-severe itch (p = 0.012). The Mendelian randomization analysis confirmed the causal relationship, with ORs of 1.043 for MMA% (p = 0.029) and 0.904 for DMA% (p = 0.077) above versus under median. Serum β-endorphin was identified as a significant biomarker for the intensity of itch (p < 0.001). Consistently, treatment with arsenite upregulated the level of β-endorphin (p = 0.002) and induced scratching bouts (p < 0.001) in mice. The randomized controlled trial in 126 participants showed that treatment with sublingual naloxone significantly relieved the intensity of itch in arsenic-exposed participants in 2 weeks (β = -0.98, p = 0.04).

CONCLUSION

Arsenic exposure is associated with pruritus, and β-endorphin serves as a biomarker of pruritus. Naloxone relieves pruritus in patients with arseniasis.

Arsenite-loaded nanoparticles inhibit the invasion and metastasis of a hepatocellular carcinoma: in vitro and in vivo study

Postoperative recurrence and metastasis are the major problems for the current treatment of hepatocellular carcinomas (HCC) in the clinic, including hepatectomy and liver transplantation. Here, we report that arsentic-loaded nanoparticles (ALNPs) are able to reduce the invasion of HCC cells in vitro, and, more importantly, can strongly suppress the invasion and metastasis of HCC in vivo without adverse side effects. Compared to free drug arsenic trioxide , ALNPs can deliver the drug into cancer cells more efficiently, destroy the structure of microtubules and reduce the aggregation of microfilaments in cell membranes more significantly. Furthermore, our results also reveal that tumor cells in murine blood were reduced remarkably after intravenous injection of ALNPs, indicating that this nano-drug may efficiently kill circulating tumor cells in vivo. In conclusion, our nano-drug ALNPs have great potential for the suppression of metastasis of HCC, which may open up a new avenue for the effective treatment of HCC without metastasis and recurrence.

Fowler's Solution and the Evolution of the Use of Arsenic in Modern Medicine

While arsenic has been used medicinally and as a poison for thousands of years, Fowler's solution, an arsenic compound, has had a fascinating history in medicine during the past 200 years. The use of Fowler's solution was first described and published as a treatment for malaria and syphilis in the late 1700s. Many clinical applications for Fowler's solutions have been studied and utilized over the years, but toxicities have limited its utility. Even so, arsenic trioxide, chemically related to Fowler's solution, was approved by the US Food and Drug Administration for treating acute promyelocytic leukemia. The history of Fowler's solution, its applications and uses, and benefits and risks are discussed.

Disruption of Mitotic Progression by Arsenic

Arsenic is an enigmatic xenobiotic that causes a multitude of chronic diseases including cancer and also is a therapeutic with promise in cancer treatment. Arsenic causes mitotic delay and induces aneuploidy in diploid human cells. In contrast, arsenic causes mitotic arrest followed by an apoptotic death in a multitude of virally transformed cells and cancer cells. We have explored the hypothesis that these differential effects of arsenic exposure are related by arsenic disruption of mitosis and are differentiated by the target cell's ability to regulate or modify cell cycle checkpoints. Functional p53/CDKN1A axis has been shown to mitigate the mitotic block and to be essential to induction of aneuploidy. More recent preliminary data suggest that microRNA modulation of chromatid cohesion also may play a role in escape from mitotic block and in generation of chromosomal instability. Other recent studies suggest that arsenic may be useful in treatment of solid tumors when used in combination with other cytotoxic agents such as cisplatin.

Down-regulation of wt1 expression in leukemia cell lines as part of apoptotic effect in arsenic treatment using two compounds

Arsenic trioxide (As2O3) induces remission in patients with acute promyelocytic leukemia (APL). To better understand molecular mechanisms of arsenic actions, this study investigated the effect of two different arsenic compounds on gene expression of apoptosis and cellular proliferation related genes. The Wilms' tumor gene (wt1) is up-regulated in acute myeloid leukemia (AML) and a variety of leukemia cell lines. The expression of wt1 in these cells is proposed to have an anti-apoptotic effect. HL-60 and K562 were treated with arsenic trioxide (As2O3) and sodium arsenite (NaAsO2) at concentrations between 0 - 10 microM for up to 48 h. The induction of apoptosis was accompanied by down-regulation of hTERT and wt1 mRNA and protein expression but up-regulation of par-4. Low concentrations of 0.1 microM arsenic induced expression of the anti-apoptotic bcl-2 gene in both cell lines HL-60 and K562. There were no major differences encountered between compounds. After arsenic treatment of the leukemia cell lines HL-60 and K562 the up-regulation of par-4 may contribute to the induction of apoptosis rather than down-regulation of bcl-2. The therapeutic effect of arsenic is the induction of apoptosis by modulating the gene expression profile of pro- and anti-apoptotic genes including the wt1 gene.

Role of heat shock protein 70 in hepatic ischemia-reperfusion injury in mice

It is well established that liver ischemia-reperfusion induces the expression of heat shock protein (HSP) 70. However, the biological function of HSP70 in this injury is unclear. In this study, we sought to determine the role of HSP70 in hepatic ischemia-reperfusion injury in mice. Male mice were subjected to 90 min of partial hepatic ischemia followed by up to 8 h of reperfusion. HSP70 was rapidly upregulated after reperfusion. To explore the function of HSP70, sodium arsenite (8 mg/kg iv) was injected before surgery. We found that this dose induced HSP70 expression within 6 h of treatment. Induction of HSP70 with arsenite resulted in a >50% reduction in liver injury as determined by serum transaminases and histology. In addition, arsenite similarly reduced liver neutrophil recruitment and liver nuclear factor-kappaB activation, and attenuated serum levels of tumor necrosis factor-alpha and macrophage inflammatory protein-2, but increased levels of interleukin (IL)-6. In HSP70 knockout mice, arsenite did not protect against liver injury but did reduce liver neutrophil accumulation. Arsenite-induced reductions in neutrophil accumulation in HSP70 knockout mice were found to be mediated by IL-6. To determine whether extracellular HSP70 contributed to the injury, recombinant HSP70 was injected before surgery. Intravenous injection of 10 microg of recombinant HSP70 had no effect on liver injury after ischemia-reperfusion. The data suggest that intracellular HSP70 is directly hepatoprotective during ischemia-reperfusion injury and that extracellular HSP70 is not a significant contributor to the injury response in this model. Targeted induction of HSP70 may represent a potential therapeutic option for postischemic liver injury.

The influence of lead and arsenite on the inhibition of human breast cancer MCF-7 cell proliferation by American ginseng root (Panax quinquefolius L.)

American ginseng root (Panax quinquefolius) has a number of purported therapeutic effects, including inhibition of cancer cell proliferation. The ability of environmentally relevant heavy metals to alter ginseng effects on cancer cell growth was the subject of this study. A water extract of American ginseng root was applied alone or in combination with physiologically relevant doses of either lead (Pb) or arsenite to MCF-7 breast cancer cells in vitro and effects on cell proliferation were determined. Ginseng alone produced a significant dose-dependent inhibition of MCF-7 cell proliferation starting at 0.5 mg ml(-1). Treatment of MCF-7 cells with 2.5 microM arsenite significantly decreased MCF-7 cell proliferation (p < 0.01). When cells were treated with arsenite (1.25 or 2.5 microM) in combination with ginseng extract (0.5 mg ml(-1)), there was an apparent synergistic inhibition of cell proliferation. Treatment of MCF-7 breast cancer cells with 50 microM Pb significantly decreased cell proliferation relative to control (p < 0.01), and concomitant ginseng and Pb treatment did not lead to a further decrease. These results suggest that contaminant heavy metals, some of which have been detected in ginseng root extracts or commercial ginseng preparations, may alter the biological activity of ginseng.

Arsenic-induced alterations in the contact hypersensitivity response in Balb/c mice

Previous studies in our laboratory indicate that arsenic alters secretion of growth promoting and inflammatory cytokines in the skin that can regulate the migration and maturation of Langerhans cells (LC) during allergic contact dermatitis. Therefore, we hypothesized that arsenic may modulate hypersensitivity responses to cutaneous sensitizing agents by altering cytokine production, LC migration, and T-cell proliferation. To investigate this hypothesis, we examined the induction and elicitation phases of dermal sensitization. Mice exposed to 50 mg/l arsenic in the drinking water for 4 weeks demonstrated a reduction in lymph node cell (LNC) proliferation and ear swelling following sensitization with 2,4-dinitrofluorobenzene (DNFB), compared to control mice. LC and T-cell populations in the draining lymph nodes of DNFB-sensitized mice were evaluated by fluorescence-activated cell sorting; activated LC were reduced in cervical lymph nodes, suggesting that LC migration may be altered following arsenic exposure. Lymphocytes from arsenic-treated animals sensitized with fluorescein isothiocyanate (FITC) exhibited reduced proliferative responses following T-cell mitogen stimulation in vitro; however, lymphocyte proliferation from nonsensitized, arsenic-treated mice was comparable to controls. Arsenic exposure also reduced the number of thioglycollate-induced peritoneal macrophages and circulating neutrophils. These studies demonstrate that repeated, prolonged exposure to nontoxic concentrations of sodium arsenite alters immune cell populations and results in functional changes in immune responses, specifically attenuation of contact hypersensitivity.

A possible relationship between bumblefoot responsive to potassium arsenite and micrococci in the blood of three birds of prey

Pododermatitis (bumblefoot) is a major health problem of falcons world-wide because healing processes in the talons are difficult and lengthy. A peregrine (Falco peregrinus), a merlin (Falco columbarius) and a saker falcon (Falco cherrug) with bumblefoot at different stages ranging from III to V, were all found to be carriers of micrococcus-like organisms in the blood and two of them were successfully treated with 0.5% potassium arsenite in low dosage given intravenously. A number of considerations are made on the immune dysfunction aspects of bumblefoot in birds of prey and on the emerging role of arsenic-based medicaments in the treatment of animal and human immune dysfunction syndromes.

Chronic fatigue syndrome (CFS) associated with Staphylococcus spp. bacteremia, responsive to potassium arsenite 0.5% in a veterinary surgeon and his coworking wife, handling with CFS animal cases

Chronic fatigue syndrome (CFS) in human patients remain a controversial and perplexing condition with emerging zoonotic aspects. Recent advances in human medicine seem to indicate a bacterial etiology and the condition has already been described in horses, dogs, cats and birds of prey in association with micrococci-like organisms in the blood. To evaluate the possibility of a chronic bacteremia, a veterinary surgeon (the author) and his coworking wife, both diagnosed with CFS and meeting the CDC working case definition, were submitted to rapid blood cultures and fresh blood smears investigations. Blood cultures proved Staph-positive and micrococci-like organisms in the blood were repeatedly observed in the 3-year period preceding the arsenical therapy, during which several medicaments, including antibiotics, proved unsuccessful. Following treatment with a low dosage arsenical drug (potassium arsenite 0.5%, im., 1 ml/12 h, for 10 days) both patients experienced complete remission. At the post-treatment control made 1 month later, micrococci had disappeared from the blood, and the CD4/CD8 ratio was raising.

Preconditioning with sodium arsenite inhibits apoptotic cell death in rat kidney with ischemia/reperfusion or cyclosporine-induced Injuries. The possible role of heat-shock protein 70 as a mediator of ischemic tolerance

This study was performed to evaluate the effect of heat-shock protein (HSP)70 induction with sodium arsenite (SA) on ischemia/reperfusion (I/R) or cyclosporin A (CsA)-induced injuries in rat kidney. Rats were classified into five groups (sham, I/R, SA+I/R, I/R+CsA and SA+I/R+CsA groups) according to both the status of SA pretreatment and treatment with CsA. SA (6 mg/kg, i.v.) pretreatment was accomplished 12 h before I/R injury, and CsA (20 mg/kg, s.c.) was given subsequent to I/R injury. The effect of SA pretreatment on I/R injury was evaluated using measurements of renal function, the histopathology score, and assays for apoptosis (DNA fragmentation analysis, TUNEL staining, mRNA expressions of the pro-apoptotic genes and caspase activities). In addition, mitochondrial morphology was examined by electron microscopy. Induction of HSP70 with SA improved both renal function and the histopathology score as compared to the group without HSP70 induction. The assays for apoptosis revealed that SA pretreatment decreased the DNA laddering pattern, TUNEL-positive cells, mRNAs expression of pro-apoptotic genes and caspase activities as compared with the group without SA pretreatment. In addition, the mitochondrial morphology was well preserved in the groups with SA pretreatment. In conclusion, SA pretreatment prevents subsequent I/R or CsA-induced injuries in the rat kidney, and this renoprotective effect appears to be mediated by induction of HSP70.