An experimental model of peripheral neuropathy induced in rats by Karwinskia humboldtiana (buckthorn) fruit

Update on Toxic Neuropathies

Purpose of Review

Toxic neuropathies are an important preventable and treatable form of peripheral neuropathy. While many forms of toxic neuropathies have been recognized for decades, an updated review is provided to increase vigilant in this area of neurology. A literature review was conducted to gather recent information about toxic neuropathies, which included the causes, clinical findings, and treatment options in these conditions.

Recent Findings

Toxic neuropathies continue to cause significant morbidity throughout the world and the causative agents, particularly with regards to medications, do not appear to be diminishing. A wide variety of causes of toxic neuropathies exist, which include alcohol, industrial chemicals, biotoxins, and medications. Unfortunately, no breakthrough treatments have been developed and prevention and symptom management remain the standard of care.

Summary

A detailed medication, occupational and hobby exposure history is critical to identifying toxic neuropathies. Increased research is warranted to identify mechanisms of neurotoxic susceptibility and potential common pathomechanistic pathways for treatment across diverse toxic neuropathies.

Neuropathic or systemic chronic intoxication with Karwinskia humboldtiana (Buckthorn) fruit? Histopathological effect in myocardial and skeletal muscle

In accidental intoxicated animals and humans, Karwinskia humboldtiana (Kh) causes lesions in the central and peripheral nervous system and organs like the kidney, liver, and lung. The objective was to evaluate the histology of myocardium and skeletal muscle after experimental chronic intoxication with mature fruit of Kh in Wistar rat. Twenty-five rats were used and divided into five groups (n = 5): four intoxicated and one control. Kh fruit was ground, dried, sieved, and administered by an orogastric tube. Intoxicated rats received 3.5 g/kg body weight fractionated in 5 doses. Control rats received only water. Animals were euthanized at 24, 48, 58, and 112 days, respectively. Samples of the myocardium and skeletal muscle were obtained and processed for light microscopy evaluation. Morphological analyses were performed, including a microdensitometric analysis. Results showed areas of necrosis in the muscle fibers, fibers with vacuolated cytoplasm, and disorganization of myofilaments, as well as staining variations in both myocardium and skeletal muscle time-depending. Zones with loss of continuity of the external lamina were identified with PAS with the diastase histochemical method. Immunolabeling with specific antibodies demonstrated diminution of actin and desmin myofilaments. The microdensitometric analysis showed a statistically significant difference between the intoxicated vs control group. These findings demonstrate that chronic intoxication of Kh fruit also causes damage in myocardial and skeletal muscle, these alterations will be useful to understand that the toxic effects of Kh fruit in accidently intoxicated humans are systemic, and not only over the nervous system.

Toxicity and Anticancer Potential of Karwinskia: A Review

Karwinskia genus consists of shrubs and small trees. Four toxic compounds have been isolated from Karwinskia plants, which were typified as dimeric anthracenones and named T496, T514, T516, and T544. Moreover, several related compounds have been isolated and characterized. Here we review the toxicity of the fruit of Karwinskia plants when ingested (accidentally or experimentally), as well as the toxicity of its isolated compounds. Additionally, we analyze the probable antineoplastic effect of T514. Toxins cause damage mainly to nervous system, liver, lung, and kidney. The pathophysiological mechanism has not been fully understood but includes metabolic and structural alterations that can lead cells to apoptosis or necrosis. T514 has shown selective toxicity in vitro against human cancer cells. T514 causes selective and irreversible damage to peroxisomes; for this reason, it was renamed peroxisomicine A1 (PA1). Since a significant number of malignant cell types contain fewer peroxisomes than normal cells, tumor cells would be more easily destroyed by PA1 than healthy cells. Inhibition of topoisomerase II has also been suggested to play a role in the effect of PA1 on malignant cells. More research is needed, but the evidence obtained so far indicates that PA1 could be an effective anticancer agent.

Peroxisomicine A1, a potential antineoplastic agent, causes micropexophagy in addition to macropexophagy

Peroxisomicine A1 (PA1) is a potential antineoplastic agent with high and selective toxicity toward peroxisomes of tumor cells. Pexophagy is a selective autophagy process that degrades damaged peroxisomes; this process has been studied mainly in methylotrophic yeasts. There are two main modes of pexophagy in yeast: macropexophagy and micropexophagy. Previous studies showed that peroxisomes damaged by a prolonged exposition to PA1 are eliminated by macropexophagy. In this work, Candida boidinii was grown in methanol-containing media, and PA1 was added to the cultures at 2 µg/mL after they reached the mid-exponential growth phase. Samples were taken at 5, 10, 15, 20, and 25 min after the addition of PA1 and processed for ultrastructural analysis. Typical morphological characteristics of micropexophagy were observed: the direct engulfment of peroxisomes by the vacuolar membrane and the presence of the micropexophagic membrane apparatus (MIPA), which mediates the fusion between the opposing tips of the vacuole to complete sequestration of peroxisomes from the cytosol. In conclusion, here we report that, in addition to macropexophagy, peroxisomes damaged by PA1 can be eliminated by micropexophagy. This information is useful to deepen the knowledge of the mechanism of action of PA1 and of that of pexophagy per se.

Peroxisomicine A1 (toxin T-514) induces cell death of hepatocytes in vivo by triggering the intrinsic apoptotic pathway

Karwinskia parvifolia possesses the highest concentration levels of the anthracenone T-514 (PA1). Studies have demonstrated the induction of apoptosis by PA1 in cancer cell lines. The aim was to investigate the effects of PA1 on the apoptosis of the mouse liver in vivo and its underlying pathway. Sixty CD-1 mice were divided into three groups: untreated, vehicle, and treated with PA1. The animals were euthanized at 4, 8, 12, and 24 h post-treatment. To confirm the toxic effect of PA1 we determined the activity of catalase. Liver sections were prepared for morphological examination and for immunohistochemical evaluation of anti and pro-apoptotic markers. DNA fragmentation was detected by TUNEL assay and electrophoresis. Pre-apoptotic mitochondrial alterations and cytochrome c oxidase activity were analyzed by transmission electron microscopy. PA1 induced pre-apoptotic mitochondrial alterations, a high activity of the cytochrome oxidase, and apoptosis in hepatocytes. PA1 caused p53 over-expression and down regulation of PCNA. PA1 also increased the expression levels of the pro-apoptotic markers Bax and Bak, whereas the anti-apoptotic molecule Bcl-2 was decreased. PA1 induces apoptosis by activating the intrinsic mitochondrial apoptotic pathway. These results will be useful for studies regarding the use of PA1 as an antineoplastic agent.

Mitochondrial ATPase activity and membrane fluidity changes in rat liver in response to intoxication with buckthorn (Karwinskia humboldtiana)

Background

Karwinskia humboldtiana (Kh) is a poisonous plant of the rhamnacea family. To elucidate some of the subcellular effects of Kh toxicity, membrane fluidity and ATPase activities as hydrolytic and as proton-pumping activity were assessed in rat liver submitochondrial particles. Rats were randomly assigned into control non-treated group and groups that received 1, 1.5 and 2 g/Kg body weight of dry powder of Kh fruit, respectively. Rats were euthanized at day 1 and 7 after treatment.

Results

Rats under Kh treatment at all dose levels tested, does not developed any neurologic symptoms. However, we detected alterations in membrane fluidity and ATPase activity. Lower dose of Kh on day 1 after treatment induced higher mitochondrial membrane fluidity than control group. This change was strongly correlated with increased ATPase activity and pH gradient driven by ATP hydrolysis. On the other hand, membrane fluidity was hardly affected on day 7 after treatment with Kh. Surprisingly, the pH gradient driven by ATPase activity was significantly higher than controls despite an diminution of the hydrolytic activity of ATPase.

Conclusions

The changes in ATPase activity and pH gradient driven by ATPase activity suggest an adaptive condition whereby the fluidity of the membrane is altered.

Karwinskia humboldtiana (buckthorn) fruit causes central nervous system damage during chronic intoxication in the rat

Karwinskia humboldtiana fruit (Kh) causes a neurological disorder 3-4 weeks after ingestion, characterized by flaccid, symmetrical, ascending paralysis, similar to the Guillain-Barre syndrome. In this polyneuropathy the lesion (demyelization) in peripheral nerves has been described in several animal species, both in acute and in chronic intoxication. However, no reports exist about the presence of lesions in the Central Nervous System (CNS), in chronic intoxication. We considered it important to evaluate, with histological techniques, the possible presence of lesions in the brain, by using a model of chronic intoxication that reproduces the same stages present in the human intoxication, to better understanding of this pathological process. In our present work we fed the ground Kh fruit to Wistar rats and samples of brain, cerebellum, and pons were embedded in paraffin. Sections were stained with Hematoxylin & Eosin (HE) and special stains for nerve tissue. Histopathological changes were evaluated in the CNS through the different stages of the polyneuropathy and comparison to a control group. With this methodology, we found lesions in the motor pathway. This is the first report about the presence of neuronal damage caused by Kh in the Central Nervous System in chronic intoxication.