Mitochondria Dysregulation in MSA
There are two categories of MSA, namely cerebellar and parkinsonian [
5,
6,
7]. In MSA patients who have a cerebellar type, ataxia is found. Ataxia is a neurological condition that impacts the lack of coordination in the movement of the muscles. Changes in the condition of this dysfunction are usually characterized by changes in the ability to speak and eye movements of an abnormal nature. Meanwhile, in MSA patients with a parkinsonian type, there is extrapyramidal motor abnormality. This neurological condition is related to lesions in the basal ganglia. This situation causes the inability of MSA sufferers to initiate changes in movement activities easily and quickly. In addition, parkinsonian-type MSA sufferers also experience muscular rigidity, and this condition is a condition of the body's muscles that contract continuously and eventually limit passive movement. Furthermore, there are also difficulties in maintaining muscle movement in the fingers, feet and other places in the body in a fixed position, commonly referred to as athetosis [
8,
9,
10].
Multiple system atrophy is closely related to α-synuclein, where α-synuclein is a synaptic protein which, in physiological conditions, is an unfolded protein produced by neuronal cells [
11,
12,
13,
14,
15]. This protein can affect mitochondria, as it is known that mitochondria are crucial cell organelles in the context of energy. The impact of α-synuclein on signalling calcium ions (Ca
2+) within the mitochondria can affect the exchange of those ions and the physical interaction between the mitochondria and the ER. Some cases, such as the low expression of A53T caused by the influence α-synuclein with mitochondria, can cause fragmentation of the mitochondria [
16,
17,
18,
19].
Localization of α-synuclein in various membranes in mitochondria can be found in MSA patients. MAM (Mitochondria-associated membranes) is a part that has a special function in the relationship between mitochondria and ER (endoplasmic reticulum), where this part functions in the regulation of mitochondrial dynamics and division also unfolded protein response [
20,
21,
22,
23]. Localization α-synuclein in this membrane will increase the uptake of Ca
2+ if it is in an overexpression state. At the same time, it will change mitochondrial morphology if it is in a downregulation condition [
16]. α-Synuclein residing in MAM demonstrated interacting with ER VAPB (Vesicle-associated membrane protein-associated protein B) [
24,
25].
α-Synuclein is also located in other parts of the mitochondria, such as OMM (Outer Mitochondrial Membrane), IMS (Inter-membrane Space), IMM (Inner Mitochondrial Membrane), and MM (Mitochondrial Matrix). In the OMM section of this protein, it is known that α-synuclein can bind to lipids and membranes [
26]. Localization of this protein is also found in dopaminergic neurons [
27]. The data show that binding α-synuclein to OMM causes mitochondrial fragmentation of both DRP1-independent and MFN [
28]. The amount of this protein that binds to OMM is known to affect mitochondrial size in both wild and A53T types of α-synuclein [
19].
Another part of the mitochondria that is the localization site of α-synuclein is the IMS (Inter-membrane Space). The interactions in this section can lead to increased ROS production and potential alteration of mitochondrial membranes. Basal conditions are also one of the conditions for α-synuclein translocation in IMS [
28,
29]. Whereas in IMM (Inner Mitochondrial Membrane), it is known that α-synuclein can bind to IMM through N-terminus [
30]. Then in MM (Mitochondrial Matrix) α-synuclein can bind to γ, B and D chains of ATP synthase. Aggregation conditions and mutations of α-synuclein cause loss of mitochondria function and accelerate the process of damage to neurodegenerative disease [
31,
32,
33,
34]. In general, translocation of α-synuclein in mitochondria is mediated by lipid binding, VDAC proteins and TIM/TOM complexes [
35,
36]. The compilation of the results of these studies is represented in
Figure 1.
Mitochondrial Reprogramming
In relation to mitochondria that are damaged in various neurodegenerative diseases, it is necessary to know that several studies target mitochondrial reprogramming. Research on mitochondrial reprogramming in MSA is minimal. However, in types of diseases such as Parkinson's disease (PD), mitochondrial impairment and research have been carried out related to mitochondrial and metabolic reprogramming. It is known that there is a mutation of the PINK1 gene in PD patients. This gene functions in the encoding of the mitochondrial kinase [
37,
38,
39,
40]. The research of Tufi et al. (2014) showed that genetic and pharmacological manipulation of nucleotide metabolism pathways could be a solution to improve mitochondrial function. Mitochondria reprogramming through the administration of folic acid and dNS (deoxyribonucleosides) through the mechanism of mitochondrial biogenesis [
41]. In addition, several studies on glucose metabolic dysfunction related to neurodegenerative diseases can also use the concept of metabolic reprogramming. It should be noted that the oxidation of glucose to CO
2 to produce ATP through the oxidative phosphorylation pathway occurs in the mitochondria. Mitochondria are the main actors in cellular energy supply, affecting amino acid synthesis and directly affecting the production of neurotransmitters and protein synthesis (
Table 1). Mitochondrial changes in neurodegenerative disease affect neuronal function [
42,
43].
Metabolic reprogramming in neurodegenerative disease can be done in various ways, namely hypoxia and exercise-induced. IHHT (intermittent hypoxia-hyperoxia training) is used in patients aged with MCI (mild cognitive impairment) conditions, which is a precursor to Alzheimer's disease. Training in using IHHT improves cognitive function in patients significantly, and it is known that decreased expression of Amyloids-β after administration of IHHT indicates a neuroprotective mechanism. Similarly, intermittent hypoxic conditioning can improve short-term memory in patients with MCI [
81,
82,
83]. While reprogramming using exercise-induced affects several points, namely an increase in temperature and blood pressure, hypoxia conditions and the impact on mitochondrial skeletal muscles, biogenesis, fusion and respiration of mitochondrial. In addition to the mitochondria in the skeletal muscle, there are several theories regarding direct neuroprotective signalling. As it is known that mitochondria not only react to signaling molecules but can be transferred between cells. Several studies have shown that systemic administration of mitochondria into the blood results in the relocation of mitochondria to brain regions and benefits mouse models of Parkinson's and Alzheimer's disease [
84,
85,
86,
87]. The possibility of using the concept in handling MSA in the future is not impossible.
Management of MSA
The treatment of MSA to date has focused on symptom management that occurs in each patient, which is very specific. This condition can occur because MSA is a multisystem disease. So various fields of science such as cardiology, neurology, urology, psychiatry, pulmonary, and dietary are needed to create a comprehensive system for handling this disease. Some MSA symptoms, namely parkinsonism, can be given Armatandine 100 mg x 3 times daily or levodopa / Carbidopa drugs (200-300 mg x 3-4 times daily) and followed by physical therapy and exercise [
88,
89,
90,
91,
92,
93]. Then, for spasticity symptoms, muscle relaxants such as tizanidine or baclofen can be used, while symptom dystonia can use trihexyphenidyl [
94,
95,
96,
97]. As it is known that symptom ataxia also occurs in MSA patients and although no medications have been able to improve this symptom significantly, intensive physical therapy can help the patient's condition [
98,
99,
100,
101,
102]. As for sleep disorders such as REM sleep behavior disorder or restless legs syndrome, MSA patients can be given clonazepam 0.5 to 2 mg at night, but if an apnea condition follows the symptoms, it is more advisable to give melatonin with an initial dose of 3 mg. During apnea, changes in sleeping position, neurostimulation and weight loss can be made [
103,
104,
105,
106,
107].
Table 2 summarizes some therapies that have been and are being carried out for MSA disease.
Low Concentration of Hydrogen Peroxide
H
2O
2 molecules are frequently regarded as poisonous molecules that have a harmful impact on numerous levels of life, both cellular and tissue [
165,
166]. Many studies, however, have discovered that the concentration of this molecule impacts the function of the molecules in the body. Low H2O2 concentrations can bring a variety of benefits. This molecule will be broken down into H
2O and ½ O
2 with the help of the enzyme catalase (CAT). The breakdown product, particularly O
2, has the potential to become an alternate supply in the body and reduce the generation of reactive oxidant species. Several studies have revealed that the H
2O
2 molecule has a variety of beneficial roles, including as a regulatory signal in metabolism [
167,
168,
169,
170,
171,
172]. H
2O
2 has a neuroprotective effect and can prevent the progression of apoptosis in PC12 cell lines at low concentrations of 10 M. This indicates that utilizing molecules at low concentrations improves mitochondrial activity [
173].