Effects of bacterial melanin on motor recovery and regeneration after unilateral destruction of Substantia Nigra pars compacta in rats

Melanin: Production from Cheese Bacteria, Chemical Characterization, and Biological Activities

Pigments are compounds of importance to several industries, for instance, the food industry, where they can be used as additives, color intensifiers, and antioxidants. As the current trend around the world is shifting to the use of eco-friendly commodities, demand for natural dyes is increasing. Melanins are pigments that are produced by several microorganisms. Pseudomonas putida ESACB 191, isolated from goat cheese rind, was described as a brown pigment producer. This strain produces a brown pigment via the synthetic Müeller-Hinton Broth. This brown compound was extracted, purified, analyzed by FTIR and mass spectrometry, and identified as eumelanin. The maximum productivity was 1.57 mg/L/h. The bioactivity of eumelanin was evaluated as the capacity for scavenging free radicals (antioxidant activity), EC₅₀ 74.0 ± 0.2 μg/mL, and as an acetylcholinesterase inhibitor, with IC₅₀ 575 ± 4 μg/mL. This bacterial eumelanin did not show cytotoxicity towards A375, HeLa Kyoto, HepG2, or Caco2 cell lines. The effect of melanin on cholesterol absorption and drug interaction was evaluated in order to understand the interaction of melanin present in the cheese rind when ingested by consumers. However, it had no effect either on cholesterol absorption through an intestinal simulated barrier formed by the Caco2 cell line or with the drug ezetimibe.

[Changes in iron content in brain structures during aging and associated neurodegenerative diseases]

The literature data on changes in the content of iron and its metabolites in brain structures during aging and neurodegenerative diseases (Parkinson's disease - PD and Alzheimer's disease - AD) are analyzed. It was revealed that with aging, the iron content in nigrostriatal formations of brain changes: the level of non-heme iron and ferritin increases and neuromelanin also accumulates in neurons of black substance. The accumulation of neuromelanin in combination with increase in ferritin content can be considered as a morphochemical sign of neuroprotective effect of nervous tissue during aging. The iron level in PD and AD compared with that during physiological aging continues to increase, and the ability of chelating agents to bind iron decreases (ferritin in neuroglia cells and neuromelanin in neurons), which activates the mechanisms of cell destruction. As a result, in PD, the aggregation of α-synuclein is disrupted, which leads to the formation of Levi bodies, and in AD, the amyloid beta precursor protein (APP) undergoes proteolysis and this leads to the formation of amyloid plaques, which triggers subsequent neurodegenerative changes, including the death of neurons.

[Morphochemical changes in the substantia nigra cellular structures in Parkinson's disease]

AIM

to clarify the features of morphochemical changes in the substantia nigra cellular structures in Parkinson's disease.

MATERIAL AND METHODS

The structural characteristics of the substantia nigra were studied microscopically and quantified using computer morphometric methods at brain autopsies of individuals with Parkinson's disease who had died from intercurrent diseases and those who had no evidence of neurological disorders in their history (a control group).

RESULTS

This investigation could clarify the features of morphochemical changes in both the neural network structures and the glial populations of the substantia nigra in Parkinson's disease. The number of neurons containing tyrosine hydroxylase (a marker of dopamine neurons) in the compact part of the substantia nigra (a ventral region) was smaller and the density distribution of Lewy bodies was higher in the patients with Parkinson's disease than in the control group. The accumulation of iron (II) compounds in the cellular elements and neuropile and the increased expression of glial fibrillary acidic protein in Parkinson's disease were more pronounced than those in the controls.

CONCLUSION

Postmortem diagnosis in Parkinson's disease should be based on a full description of a set of neuronal and glial morphochemical and structural changes in the substantia nigra rather than on the identification of cellular markers for the neurodegenerative process.

Detection of Ca(2+)-dependent acid phosphatase activity identifies neuronal integrity in damaged rat central nervous system after application of bacterial melanin

The study aims to confirm the neuroregenerative effects of bacterial melanin (BM) on central nervous system injury using a special staining method based on the detection of Ca(2+)-dependent acid phosphatase activity. Twenty-four rats were randomly assigned to undergo either unilateral destruction of sensorimotor cortex (group I; n = 12) or unilateral rubrospinal tract transection at the cervical level (C3-4) (group II; n = 12). In each group, six rats were randomly selected after surgery to undergo intramuscular injection of BM solution (BM subgroup) and the remaining six rats were intramuscularly injected with saline (saline subgroup). Neurological testing confirmed that BM accelerated the recovery of motor function in rats from both BM and saline subgroups. Two months after surgery, Ca(2+)-dependent acid phosphatase activity detection in combination with Chilingarian's calcium adenoside triphosphate method revealed that BM stimulated the sprouting of fibers and dilated the capillaries in the brain and spinal cord. These results suggest that BM can promote the recovery of motor function of rats with central nervous system injury; and detection of Ca(2+)-dependent acid phosphatase activity is a fast and easy method used to study the regeneration-promoting effects of BM on the injured central nervous system.

Bacterial melanin promotes recovery after sciatic nerve injury in rats

Bacterial melanin, obtained from the mutant strain of Bacillus Thuringiensis, has been shown to promote recovery after central nervous system injury. It is hypothesized, in this study, that bacterial melanin can promote structural and functional recovery after peripheral nerve injury. Rats subjected to sciatic nerve transection were intramuscularly administered bacterial melanin. The sciatic nerve transected rats that did not receive intramuscular administration of bacterial melanin served as controls. Behavior tests showed that compared to control rats, the time taken for instrumental conditioned reflex recovery was significantly shorter and the ability to keep the balance on the rotating bar was significantly better in bacterial melanin-treated rats. Histomorphological tests showed that bacterial melanin promoted axon regeneration after sciatic nerve injury. These findings suggest that bacterial melanin exhibits neuroprotective effects on injured sciatic nerve, contributes to limb motor function recovery, and therefore can be used for rehabilitation treatment of peripheral nerve injury.

Bacterial melanin improves cognitive impairment induced by cerebral hypoperfusion in rats

The effect of bacterial melanin (BM) solution on learning and memory impairment induced by chronic cerebral hypoperfusion in rats was studied. Male rats were injected intramuscularly with BM solution on the second day after bilateral permanent occlusion of the common carotid artery. Rats received 6 mg/ml (170 mg/kg) BM and performed significantly better in cognition tests compared with controls. The present findings demonstrate that the beneficial effects of BM injection on cognitive functions may be due to preventing neuropathological alterations, suppressing the inflammation process, stimulating vascularization and inhibiting oxidative damage. Obtained data suggest that BM has therapeutic potential for the treatment of neurodegeneration caused by ischemia.