The BMC Med-Dai Fangyin team has made important progress in constructing a Parkinson's syndrome model and evaluating efficacy by using silkworms

Parkinson's disease (PD) is the most common neurodegenerative disease other than Alzheimer's disease, PD, in middle-aged and elderly people The pathology is characterized by degeneration and death of dopaminergic neurons in the substantia nigra, as well as a significant reduction in dopamine content [1, 2], inducing a large number of movement disorders (eg, limb weakness, stiffness, tachycardia, and postural instability) and non-movement disorders (eg, autoimmune diseases) [3, 4].

。 The nervous system of PD patients usually exhibits high oxidative damage, and excessive accumulation of free radicals is known to lead to oxidative damage of endogenous macromolecules, thereby inducing a series of cell death events [5].

Studies have shown that more than 12 million people are expected to be diagnosed with PD by 2040 [6,7].

So far, the pathogenesis of PD has not been fully explained, and there is no radical cure in the clinic, and the creation of new animal models and the screening of therapeutic drugs help to accelerate the elucidation of the pathogenic mechanism of PD and the discovery
of effective treatment strategies.

On October 28, 2022, Professor Dai Fangyin's team from Southwest University presented a report on BMC Medicine ( BMC Medicine) published a report entitled "Lycium barbarum polysaccharide improves.
" dopamine metabolism and symptoms in an MPTP-induced model of Parkinson’s disease", using silkworms to build a model of Parkinson's syndrome and evaluate the effectiveness of therapeutic drugs
.
Young teachers Associate Professor Song Jiangbo, Master Student Liu Lian and Dr.
Li Zhiquan of the University of Copenhagen in Denmark are co-first authors of the paper, Dai Fangyin The professor is the corresponding author
of the paper.
In this study, the authors added 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP) induced the creation of a PD silkworm model, which exhibits many symptoms similar to the pathological features typical of human sporadic PD, such as impaired exercise capacity, decreased dopamine levels, Dopaminergic neurons are damaged and levels of oxidative stress are elevated
.
The pathological model was systematically evaluated using the clinical drug levodopa for the treatment of human PD, and a traditional Chinese medicine active ingredient with good efficacy for PD, Lycium barbarum, was found after screening polysaccharide，LBP）
。

Many previous studies have shown that MPTP can induce animal models of Parkinson's syndrome [8, 9].

In order to explore whether MPTP can be modeled in silkworms and the optimal concentration required for modeling, the researchers fed silkworms different concentrations of MPTP and found MPTP There was an inverse correlation between dose administration and individual survival, with higher survival rates in the 125 μm MPTP group compared with 250 μm and 500 μm (Figure 1A).
There were no obvious abnormalities in the growth and development of silkworms (Figure 1B).

There was also no significant difference in mean body weight compared to the control group (Figure 1C).

By measuring the motor (grip, flip, abdominal curvature) ability and voluntary motion trajectory and rate of the 125 μm MPTP group, it was found that the grip duration was shorter (Figure 1D) and the time required to complete a complete flip and abdominal curvature recovery was longer (Figure 1E, F).
, the range and rate of free motion are significantly reduced (Figure 1G, H).

A significant reduction in the content of the neurotransmitter dopamine in the brain is an important clinical diagnostic marker for PD
.
By investigating dopamine metabolism in the induction group by fluorescence quantification, immunofluorescence, and enzyme viability assays, the researchers found a significant reduction in brain dopamine content in the 125 μm MPTP group (Figure 1I).

The mRNA and protein content and catalytic activity of tyrosine hydroxylase (TH), a key enzyme required in dopamine synthesis, were significantly reduced (Figure 1J-L).
Transcription levels of DOPA decarboxylase (DDC), another key enzyme of dopa metabolism, also occurred significantly (Figure 1M), PRKN with dopaminergic neurons and oxidative stress protection The expression level of genes was also significantly reduced (Figure 1N), the total antioxidant capacity was significantly reduced, and the oxidation products were significantly increased (Figure 1O, P).

The above evidence shows that MPTP-induced silkworm models can reproduce the pathological characteristics
of human PD relatively completely.

Fig.
1 The MPTP-induced PD silkworm model was able to reproduce multiple pathological features of human PD

(Source: Song JB, et al.
, BMC Medicine, 2022).

To further demonstrate the usability of this newly created silkworm model of Parkinsonism, the authors fed animal models of Parkinsonism with the drugs levodopa (LD) and Carbidopa (CD) for the clinical treatment of human PD The mixture, which then measured the response in animal models, found PD when an MPTP-induced animal model of PD was eaten with a mixture of LD and CD Silkworms were significantly regained in motor activity, significantly improved grip, and less time-consuming in flipping and abdominal curvature tests (Figure 2A–C).

At the same time, the dopamine content determination showed that LD-CD significantly restored the dopamine content in the PD silkworm brain (Figure 2D).

In addition, immunofluorescence analysis of brain tissue sections showed significant mitigation of TH protein levels, but no significant change in TH activity (Figure 2E, F).

To further investigate the restorative effect of LD-CD mixture on dopamine metabolism, the authors found a significant increase in DDC expression levels in PD models supplemented with LD-CD (Figure 2G).

Similarly, PRKN expression levels were significantly increased (Figure 2H), while antioxidant capacity was not significantly improved (Figure 2I).

Fig.
2 LD-CD mixture of PD clinical treatment has a good therapeutic effect on MPTP-induced PD silkworm model

(Source: Song JB, et al.
, BMC Medicine, 2022).

LBP has been shown to have oxidative stress defense and optic nerve protection [10, 11], as well as protection of PC12 cells from rotenone and rotenone and 6 Hydroxydopamine-induced apoptosis [12,13].

Therefore, the authors speculate that LBP may have a similar biological effect
on alleviating the lesions of dopaminergic neurons in Parkinson's patients.
It was found that LBP enhanced the grasping ability of 5-year-old larvae and significantly shortened the time required for PD silkworms to turn over and recover from abdominal curvature (Figure 3A–C).

Interestingly, by measuring the dopamine content in PD silkworm brain by UPLC, it was found that the dopamine content in PD silkworm brain in the LBP treatment group was significantly increased.
The results of ELISA showed that the TH enzyme activity of PD silkworms was significantly increased after LBP feeding.
Immunofluorescence quantification of TH protein levels in brain tissue further confirms this finding (Figure 3D-F).

At the same time, LBP restored the transcription levels of DDC and PRKN, key genes for the regulation of dopa metabolism in the brain of PD silkworms (Figure 3G, H).

。 In addition, the total antioxidant capacity in the silkworm brain increased and the content of the oxidation product MDA decreased (Figure 3I, J).

These results show that, similar to the LD and CD combination, LBP significantly improves MPTP-induced PD The pathological symptoms of silkworms even have a more prominent effect
in restoring TH enzyme activity and oxidative damage repair.

Fig.
3 LBP has a good therapeutic effect on MPTP-induced PD silkworm model

(Source: Song JB, et al.
, BMC Medicine, 2022).

Figure 4 Work summary schematic: Silkworm construction of Parkinson's syndrome model and efficacy evaluation

(Source: Song JB, et al.
, BMC Medicine, 2022).

In summary, the authors created a novel PD model
in silkworms by oral administration of the neurotoxin MPTP.
This model presents impaired
motor function, decreased dopamine content, and increased oxidative stress consistent with the pathological features of human PD.
LD, the direct precursor of dopamine, can be transferred to the brain through mechanisms that promote amino acid transport [14]
.
Due to its efficacy and cost-effectiveness, oral LD is the most commonly used and effective method
for the treatment of PD.
In addition to dopamine deficiency, treatment of Parkinson's disease focuses on protecting dopaminergic neurons and reversal
of impaired motor function.
Interestingly, the authors identified through screening a novel native molecule of LBP, which normalizes PD-like symptoms and molecular alterations with outstanding therapeutic effects in restoring motility and protecting dopaminergic neurons, particularly dopamine metabolism and redox homeostasis (Figure 4).

。 In the future, this model can be used to further investigate the etiology of PD, especially the process of dopamine metabolism, and play to its innate advantage
of high throughput and low cost for primary drug screening targeting PD.
In general, in the development of animal models of diseases using silkworms as the model, this study is the first to penetrate the construction of animal models of human diseases, the evaluation of therapeutic drugs and the screening of new drugs, which not only provides a new animal model for the study of the pathogenic mechanism of PD, but also provides a certain direction
for the research and development of new therapeutic drugs.

Original link: https://bmcmedicine.
biomedcentral.
com/articles/10.
1186/s12916-022-02621-9#citeas

Professor Dai Fangyin is the corresponding author of the paper, Associate Professor Song Jiangbo is the first author of the paper, master student Liu Lian and Dr.
Li Zhiquan of the University of Copenhagen are co-first authors, and this research is supported
by the National Natural Science Foundation of China and other projects.

First authors: Song Jiangbo (first from left), Liu Lian (second from left), Li Zhiquan (second from right); Corresponding author: Dai Fangyin (first from right).

(Photo courtesy of State Key Laboratory of Silkworm Genomic Biology)