Low copper and brain abnormalities in fetus from triethylene tetramine dihydrochloride-treated pregnant mouse

Triethylenetetramine (TETA)

The WEEL for triethylenetetramine (TETA; CAS No. 112-24-3) was originally established in 1991 and updated in 1998 and 2009. Recent literature searches to identify new toxicity information were performed in 2016 and January 2021. No new studies or data relevant to the WEEL were identified. TETA is used in manufacturing; the hydrochloride salt of TETA is used as a copper-chelating drug in the treatment of Wilson's disease. TETA is severely irritating to the skin and eyes and produces skin sensitization; however, it is of low to moderate acute toxicity via the oral and dermal routes of exposure. In subchronic studies, signs of toxicity included multi-organ effects (lung, liver, and spleen) in mice, but not rats. TETA was genotoxic/mutagenic in short-term in vitro assays but not in in vivo assays. No data on reproductive toxicity were available. Embryo/fetal toxicity occurred at maternally toxic doses and was associated with copper deficiency. In humans, the use of TETA·2HCl for treatment of Wilson's disease during pregnancy resulted in no miscarriages or fetal abnormalities. No evidence of carcinogenicity was noted in a lifetime dermal study in mice. Based on a subchronic drinking water study in mice, 600 ppm (95 mg/kg-day) was determined to be the no-observed-adverse-effect level (NOAEL) and the point of departure (POD). This NOAEL was converted to an equivalent inhalation concentration by adjusting for respiratory rate, interindividual variability, and uncertainty. The resulting 8-h time-weighted average WEEL value of 1 ppm is expected to provide a significant margin of safety against any potential adverse health effects in workers exposed to airborne TETA.

Novel therapeutic approaches to the treatment of Wilson’s disease

The treatment of Wilson's disease has changed considerably in recent times, from the use of penicillamine (Cuprimine, Merck) for all stages and types of disease, to the use of three other anticopper drugs at appropriate times for appropriate patients. Each type and stage of the disease can be considered as a therapeutic target, for which specialised therapy is appropriate. This paper systematically reviews the various types and stages of Wilson's disease presentation, and provides opinion on the appropriate therapy for each. For patients presenting with neurological disease, the use of tetrathiomolybdate is optimum; for patients presenting with mild-to-moderate hepatic failure, a combination of trientine (Syprine, Merck) and zinc is recommended, whereas liver transplantation is necessary for those with severe failure; zinc therapy alone or trientine alone as second choice is recommended for patients presenting with hepatitis or cirrhosis without liver failure, for maintenance therapy, for treatment of presymptomatic patients and for treatment of paediatric and pregnant patients.

The copper chelator trientine has an antiangiogenic effect against hepatocellular carcinoma, possibly through inhibition of interleukin-8 production

Recent studies have revealed that copper is an important cofactor for several angiogenic agents. We examined the antiangiogenic effect against hepatocellular carcinoma (HCC) of the copper chelator trientine, especially focusing on the relationship between copper and interleukin-8 (IL-8), a potent angiogenic factor produced by hepatoma cells. HuH-7 hepatoma cells were transplanted into nude mice and the growth of xenograft tumors was compared to and without administration of trientine. Using the resected tumor, microvessel density, apoptotic potential and proliferative activity were analyzed histologically and IL-8 mRNA was semiquantified by RT-PCR. In addition, HuH-7 cells were cultured in control medium, medium supplemented with copper, medium supplemented with trientine and medium supplemented with both copper and trientine. Human IL-8 levels were measured in the supernatants by ELISA. Using the extracts from cultured cells, IL-8 mRNA was semiquantified by RT-PCR. Trientine suppressed the growth of xenograft tumors significantly. Histologically, apoptotic potential was increased significantly and microvessel density, decreased. The production of IL-8 from the tumor was suppressed by trientine. In vitro, IL-8 production by HuH-7 cells in copper-containing medium was significantly greater than that in copper-free medium, and this effect was weakened when trientine was added. However, no significant change was apparent when trientine was added to the medium alone. In conclusion, the chelating effect of trientine prevented copper from functioning as a cofactor in angiogenesis, which resulted in reduced IL-8 production from HuH-7 cells.

Increased susceptibility of copper-deficient neuroblastoma cells to oxidative stress-mediated apoptosis

Treatment of neuroblastoma cells with the copper chelator triethylene tetramine tetrahydrochloride induced intracellular decrease of copper content paralleled by diminished activity of the enzymes Cu, Zn superoxide dismutase, and cytochrome c oxidase. This effect appears to be specific for copper-enzymes and the treatment affects neither viability nor growth capability of cells. However, molecular markers of apoptosis Bcl-2, p53, and caspase-3 were slightly affected in these cells. When copper-deficient cells were challenged with oxidative stress generated by paraquat or puromycin, they underwent a higher degree of apoptosis with respect to copper-adequate control cells. The mechanism underlying paraquat-triggered apoptosis implies dramatic activation of caspase-3 and induction of the transcription factor p53. These results demonstrate that impairment of copper balance predisposes neuronal cells to apoptosis induced by oxidative stress. Overall findings represent a contribution to the comprehension of the link between copper-imbalance and neurodegeneration, which has recently been repeatedly suggested for the most invalidating pathologies of the central nervous system.

Treatment of Wilson's disease with zinc. XVII: treatment during pregnancy

Therapy of Wilson's disease continues to evolve. In 1997, zinc acetate was added to the list of drugs approved by the Food and Drug Administration, which includes penicillamine and trientine. The mechanism of zinc's anticopper action is unique. It induces intestinal cell metallothionein, which binds copper and prevents its transfer into blood. As intestinal cells die and slough, the contained copper is eliminated in the stool. Thus, zinc prevents the intestinal absorption of copper. It is universally agreed that pregnant Wilson's disease patients should remain on anticopper therapy during pregnancy. There are numerous reports of such patients stopping penicillamine therapy to protect their fetus from teratogenicity, only to undergo serious deterioration and even death from renewed copper toxicity. Penicillamine and trientine have teratogenic effects in animals, and penicillamine has known teratogenic effects in humans. In this report we discuss the results of 26 pregnancies in 19 women who were on zinc therapy throughout their pregnancy. The evidence is good that zinc protects the health of the mother during pregnancy. Fetal outcomes were generally quite good, although one baby had a surgically correctable heart defect and one had microcephaly.