Oral aluminum administration during pregnancy and lactation produces gastric and renal lesions in rat mothers and delay in CNS development of their pups

Is the Aluminum Hypothesis dead?

The Aluminum Hypothesis, the idea that aluminum exposure is involved in the etiology of Alzheimer disease, dates back to a 1965 demonstration that aluminum causes neurofibrillary tangles in the brains of rabbits. Initially the focus of intensive research, the Aluminum Hypothesis has gradually been abandoned by most researchers. Yet, despite this current indifference, the Aluminum Hypothesis continues to attract the attention of a small group of scientists and aluminum continues to be viewed with concern by some of the public. This review article discusses reasons that mainstream science has largely abandoned the Aluminum Hypothesis and explores a possible reason for some in the general public continuing to view aluminum with mistrust.

Aluminum induces neurofilament aggregation by stabilizing cross-bridging of phosphorylated c-terminal sidearms

Exposure to neurotoxin aluminum neurotoxicity is accompanied by the perikaryal accumulation of tangles of phosphorylated neurofilaments (NFs). We examined their formation and reversibility under cell-free conditions. AlCl3 induced dose-dependent formation of NF aggregates, ultimately incorporating 100% of detectable NFs. The same concentration of CaCl2 induced approximately 25% of NFs to form longitudinal dimers and did not induce aggregation. AlCl3 induced similar percentages of aggregates in the presence or absence of CaCl2, and CaCl2 could not reduce pre-formed aggregates. CaCl(2)-induced dimers and AlCl(3)-induced aggregates were prevented by prior NF dephosphorylation. While CaCl(2)-induced dimers were dissociated by phosphatase treatment, AlCl(3)-induced aggregates were only reduced by approximately 50%, suggesting that aggregates may sequester phosphorylation sites. Since phosphatases regulate NF phosphorylation within perikarya, inhibition of NF dephosphorylation by aluminum would promote perikaryal NF phosphorylation and foster precocious phospho-dependent NF-NF associations. These findings are consistent with the notion that prolonged interactions induced among phospho-NFs by the trivalent aluminum impairs axonal transport and promotes perikaryal aggregation.

Does aluminum exposure of pregnant animals lead to accumulation in mothers or their offspring?

There is concern that environmental and dietary aluminum (Al) might cause developmental toxicity. To better understand this concern, we reviewed published studies which administered Al compounds to pregnant animals and measured accumulation of Al in mother, fetus, or born offspring. A total of 7 studies were identified which administered Al during gestation and evaluated fetal accumulation. Another 7 studies administered Al at least until birth and then evaluated accumulation in mothers and/or pups. These 14 studies included 4 different Al compounds (hydroxide, chloride, lactate, and citrate) administered by 4 different routes (gavage, feed, intraperitoneal injection, and subcutaneous injection) with total doses ranging from 13.5 to 8,400 mg/kg. Fetal Al levels were not increased in 6 of 7 studies and pup Al levels were not increased in 4 of 5 studies in which they were measured. Maternal Al levels were increased in some studies, but there was no consistent pattern of organ-specific accumulation and several positive studies were contradicted by subsequent reports from the same laboratory. Placental levels were increased in 6 of 9 studies and were greater than corresponding fetal levels. The weight of evidence in these studies suggests that environmental and dietary Al exposures are unlikely to pose risks of Al accumulation to pregnant animals or their fetuses.