Chemistry of Pesticides: Toxic Chemical Lindane and the Blood-Brain Barrier

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Home / Chemistry of Pesticides: Toxic Chemical Lindane and the Blood-Brain Barrier
beta-isomer of Lindane

Lindane’s chemical structure allows it to pass the blood-brain barrier. Image courtesy of the National Library of Medicine.

Pesticides are toxic to pests – but how much damage can they do to humans? In many cases, we depend on the blood-brain barrier to protect our most critical system from the poisonous chemicals.

The blood-brain barrier regulates the natural evolutionary response of defending the brain from toxins. However, the blood-brain-barrier, as a concept, is relatively new and was first ‘observed’ in 1885. It took 100 years of scientific work before the discovery was put on solid footing.

How Does The Blood-Brain Barrier Work?

Simply put, a majority of the substances in our environment are toxic to the human brain, so this barrier is a highly controlled gateway. Unfortunately, the pesticide Lindane, a toxic chemical, can get through.

Lindane Breaches Blood/Brain Barrier: Why?

When Lindane enters the human body, whether it absorbs through the skin or from the gut, it is not metabolized but finds its way throughout the body. It is eventually excreted through feces or urine in many cases.

There are two oft-cited reasons for Lindane’s persistent nature.

One reason for the non-metabolizing nature of this chemical is the lack of bio-chemically recognizable groupings. There are no alcohol-type appendages, nor amino acid type appendages. Lindane does not resemble any natural biochemical. Instead, it possesses carbon, hydrogen, and chlorine atoms.

The second reason for persistence is the few biological entities that are known to metabolize the substance.

For these two cited reasons, lindane can dissolve in fat. As a fat-soluble or highly lipophilic substance, it can and will pass through the blood-brain barrier.

Lindane in the Brain

Once in the brain, Lindane will induce swelling, inflammation and subsequent neural degeneration. When a ‘toxin’ enters the brain it takes a period of time until the body responds. The mechanisms by which neural degeneration takes place are not well understood but most hypotheses rest upon the brain’s immune response.

An avenue of current thinking addresses the immune response of brain’s  microglial cells. These cells attack diseased-or-damaged parts of the brain. Although it seems problematic to think of brain cells devouring other brain cells, that is the case.

Extracellular Histone H1

In an interesting development from mid-2013, researchers from the UK and Sweden identified a potential neural protein (associated with the microglial cell) that serves as a killer-protein. This killer-protein, known as a histone, was sequenced and identified as extracellular histone H1.

Polypeptide H1

Polypeptide H1 is implicated in neural degeneration. Image courtesy of the U.S. National Library of Medicine.

Generally speaking, histones are polypeptide proteins (long chains of amino acids) that are found primarily in the nucleus of a cell. Current research lists five flavors of histone: H1 to H5.

However, according to the cited work of Gilthorpe, histone H1 is not directly associated with the nucleus but resides in the cytoplasm of microglial brain cells.

Researchers cite that interactions between H1 and damaged cells will facilitate the removal of affected brain cells. The idea of ‘removing affected brain cells’ is currently a hypothesis that needs further confirmation. However, if true, it would be a radical departure for H1 polypeptides.

H1 Protein, Lindane, and Neural Degeneration

In the last two decades, increasing evidence points at the H1 protein and  Lindane being found within post-mortem, brain tissue of Parkinson’s patients.

Although there is no ‘real smoking gun’ at present, researchers are focusing their skills upon the blood-brain-barrier, organo-chlorine pesticides, H1, and Parkinson’s disease.

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