1.Mechanism of Traditional Chinese Medicine in Treating Steroid-Induced Osteonecrosis of Femoral Head via Regulating PI3K/Akt Pathway: A Review
Yaqi ZHANG ; Bo LI ; Jiancheng TANG ; Ran DING ; Cheng HUANG ; Yaping XU ; Qidong ZHANG ; Weiguo WANG
Chinese Journal of Experimental Traditional Medical Formulae 2025;31(5):141-149
Steroid-induced osteonecrosis of the femoral head (SONFH) is a severe musculoskeletal disorder often induced by the prolonged or excessive use of glucocorticoids. Characterized by ischemia of bone cells, necrosis, and trabecular fractures, SONFH is accompanied by pain, femoral head collapse, and joint dysfunction, which can lead to disability in severe cases. The pathogenesis of SONFH involves hormone-induced osteoblast apoptosis, bone microvascular endothelial cell (BMEC) apoptosis, oxidative stress, and inflammatory responses. The phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway plays a pivotal role in the development of the disease. Modulating the PI3K/Akt signaling pathway can promote Akt phosphorylation, thereby stimulating the osteogenic differentiation of bone marrow mesenchymal stem cells and osteoblasts, promoting angiogenesis in BMECs, and inhibiting osteoclastogenesis. The research on the treatment of SONFH with traditional Chinese medicine (TCM) has gained increasing attention. Recent studies have shown that TCM monomers and compounds have potential therapeutic effect on SONFH by intervening in the PI3K/Akt signaling pathway. These studies not only provide a scientific basis for the application of TCM in the treatment of SONFH but also offer new ideas for the development of new therapeutic strategies. This review summarized the progress in Chinese and international research on the PI3K/Akt signaling pathway in SONFH over the past five years. It involved the composition and transmission mechanisms of the signaling pathway, as well as its regulatory effects on osteoblasts, mesenchymal stem cells, osteoclasts, BMECs, and other cells. Additionally, the review explored the TCM understanding of SONFH and the application of TCM monomers and compounds in the intervention of the PI3K/Akt pathway. By systematically analyzing and organizing these research findings, this article aimed to provide references and point out directions for the clinical prevention and treatment of SONFH and promote further development of TCM in this field. With in-depth research on the PI3K/Akt pathway and the modern application of TCM, it is expected to bring safer and more effective treatment options for patients with SONFH.
2.Ferroptosis and osteoporosis
Cheng YANG ; Weimin LI ; Dongcheng RAN ; Jiamu XU ; Wangxiang WU ; Jiafu XU ; Jingjing CHEN ; Guangfu JIANG ; Chunqing WANG
Chinese Journal of Tissue Engineering Research 2025;29(3):554-562
BACKGROUND:It has also been confirmed that ferroptosis is closely related to a variety of musculoskeletal diseases,such as rheumatoid arthritis,osteosarcoma,and osteoporosis.The pathophysiological mechanisms of ferroptosis and osteoporosis need to be further studied and elucidated to broaden our understanding of iron metabolism and osteoporosis.It will provide research ideas for the future elucidation of new mechanisms of osteoporosis and the development of new technologies and drugs for the treatment of osteoporosis. OBJECTIVE:To provide an overview of the current status of research on ferroptosis in osteoporosis,to provide a new direction for future research on the specific molecular mechanisms of osteoporosis,and to provide more effective and better options for osteoporosis treatment strategies. METHODS:The first author used the computer to search the literature published from 2000 to 2024 in CNKI,WanFang,VIP,and PubMed databases with search terms"ferroptosis,iron metabolism,osteoporosis,osteoblast,osteoclast,bone metabolism,signal pathway,musculoskeletal,review"in Chinese and English.A total of 68 articles were finally included according to the selection criteria. RESULTS AND CONCLUSION:(1)Ferroptosis is a new type of cell death discovered in recent years,which is usually accompanied by a large amount of iron accumulation and lipid peroxidation during cell death,and its occurrence is iron-dependent.This is distinctly different from several types of cell death that are currently being hotly studied(e.g.,cellular pyroptosis,necrotic apoptosis,cuproptosis,and autophagy).(2)Intracellular iron homeostasis is manifested as a balance between iron uptake,export,utilization,and storage.The body's iron regulatory system includes systemic and intracellular regulation.The main factor of systemic regulation is hepcidin produced by hepatic secretion,and cellular regulation depends on the iron regulatory protein/iron response element system.Of course,intracellular iron homeostasis can be controlled by other factors,such as hypoxia,cytokines,and hormones.(3)Lipid peroxidation causes oxidative damage to biological membranes(plasma membrane and internal organelle membranes),lipoproteins,and other lipid-containing molecules.Polyunsaturated fatty acid-containing phospholipids are important targets of lipid peroxidation.Free polyunsaturated fatty acid is an important substrate for lipid oxidation and can bind to the phospholipid bilayer,leading to over-oxidation and thus triggering lipid apoptosis.(4)Several studies have shown that osteoblasts are overloaded with iron in different ways,resulting in the accumulation of unstable ferrous iron and the generation of reactive oxygen species and lipid peroxides,causing ferroptosis of osteoblasts and ultimately a decrease in bone formation,affecting bone homeostasis and the development of osteoporosis.(5)Osteoclasts are large multinucleated cells formed by the fusion of mononuclear macrophage cell lines or bone marrow mesenchymal stem cells induced by nuclear factor-κB ligand receptor activator,and they have the function of bone resorption.Iron ions can promote osteoclast differentiation and bone resorption through the production of intracellular lipid reactive oxygen species,while iron chelators can inhibit osteoclast formation in vitro and thus affect the occurrence and development of osteoporosis.
3.Inhibition of HDAC3 Promotes Psoriasis Development in Mice Through Regulating Th17
Fan XU ; Xin-Rui ZHANG ; Yang-Chen XIA ; Wen-Ting LI ; Hao CHEN ; An-Qi QIN ; Ai-Hong ZHANG ; Yi-Ran ZHU ; Feng TIAN ; Quan-Hui ZHENG
Progress in Biochemistry and Biophysics 2025;52(4):1008-1017
ObjectiveTo investigate the influence of histone deacetylase 3 (HDAC3) on the occurrence, development of psoriasis-like inflammation in mice, and the relative immune mechanisms. MethodsHealthy C57BL/6 mice aged 6-8 weeks were selected and randomly divided into 3 groups: control group (Control), psoriasis model group (IMQ), and HDAC3 inhibitor RGFP966-treated psoriasis model group (IMQ+RGFP966). One day prior to the experiment, the back hair of the mice was shaved. After a one-day stabilization period, the mice in Control group was treated with an equal amount of vaseline, while the mice in IMQ group was treated with imiquimod (62.5 mg/d) applied topically on the back to establish a psoriasis-like inflammation model. The mice in IMQ+RGFP966 group received intervention with a high dose of the HDAC3-selective inhibitor RGFP966 (30 mg/kg) based on the psoriasis-like model. All groups were treated continuously for 5 d, during which psoriasis-like inflammation symptoms (scaling, erythema, skin thickness), body weight, and mental status were observed and recorded, with photographs taken for documentation. After euthanasia, hematoxylin-eosin (HE) staining was used to assess the effect of RGFP966 on the skin tissue structure of the mice, and skin thickness was measured. The mRNA and protein expression levels of HDAC3 in skin tissues were detected using reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot (WB), respectively. Flow cytometry was employed to analyze neutrophils in peripheral blood and lymph nodes, CD4+ T lymphocytes, CD8+ T lymphocytes in peripheral blood, and IL-17A secretion by peripheral blood CD4+ T lymphocytes. Additionally, spleen CD4+ T lymphocyte expression of HDAC3, CCR6, CCR8, and IL-17A secretion levels were analyzed. Immunohistochemistry was used to detect the localization and expression levels of HDAC3, IL-17A, and IL-10 in skin tissues. ResultsCompared with the Control group, the IMQ group exhibited significant psoriasis-like inflammation, characterized by erythema, scaling, and skin wrinkling. Compared with the IMQ group, RGFP966 exacerbated psoriasis-like inflammatory symptoms, leading to increased hyperkeratosis. The psoriasis area and severity index (PASI) skin symptom scores were higher in the IMQ group than those in the Control group, and the scores were further elevated in the IMQ+RGFP966 group compared to the IMQ group. Skin thickness measurements showed a trend of IMQ+RGFP966>IMQ>Control. The numbers of neutrophils in the blood and lymph nodes increased sequentially in the Control, IMQ, and IMQ+RGFP966 groups, with a similar trend observed for CD4+ and CD8+ T lymphocytes in the blood. In skin tissues, compared with the Control group, the mRNA and protein levels of HDAC3 decreased in the IMQ group, but RGFP966 did not further reduce these expressions. HDAC3 was primarily located in the nucleus. Compared with the Control group, the nuclear HDAC3 content decreased in the skin tissues of the IMQ group, and RGFP966 further reduced nuclear HDAC3. Compared with the Control and IMQ groups, RGFP966 treatment decreased HDAC3 expression in splenic CD4+ and CD8+ T cells. RGFP966 treatment increased the expression of CCR6 and CCR8 in splenic CD4+ T cells and enhanced IL-17A secretion by peripheral blood and splenic CD4+ T lymphocytes. Additionally, compared with the IMQ group, RGFP966 reduced IL-10 protein levels and upregulated IL-17A expression in skin tissues. ConclusionRGFP966 exacerbates psoriatic-like inflammatory responses by inhibiting HDAC3, increasing the secretion of the cytokine IL-17A, and upregulating the expression of chemokines CCR8 and CCR6.
4.Alanine transferase test results and exploration of threshold adjustment strategies for blood donors in Shenzhen, China
Xin ZHENG ; Yuanye XUE ; Haobiao WANG ; Litiao WU ; Ran LI ; Yingnan DANG ; Tingting CHEN ; Xiaoxuan XU ; Xuezhen ZENG ; Jinfeng ZENG
Chinese Journal of Blood Transfusion 2025;38(4):488-494
[Objective] To conduct a retrospective statistical comparison of alanine aminotransferase (ALT) test values in blood donors prior to blood collection, aiming to analyze the objective characteristics of the population with elevated ALT levels (ALT>50 U/L) and provide reference data for adjusting the screening eligibility threshold for ALT. [Methods] The preliminary ALT screening data of 30 341 blood donor samples collected prior to blood donation from three smart blood donation sites at the Shenzhen Blood Center between 2022 and 2023 were extracted and compared with data from a health examination department of a tertiary hospital in Shenzhen (representing the general population, n=24 906). Both datasets were categorized and statistically described. A retrospective analysis was conducted to examine the associations between ALT test results and factors such as donors' gender, age, ethnicity, donation site, donation season, and frequency of blood donation. [Results] The ALT levels in both blood donors and the general population were non-normally distributed. The 95th percentile of ALT values was calculated as 61.4 U/L (male: 67.8 U/L, female: 39.3 U/L) for blood donors and 58.1 U/L (male: 63.7 U/L, female: 51.2 U/L) for the general population. The non-compliance rates (ALT>50 U/L) were 7.65% (2 321/30 341) in blood donors and 7.08% (1 763/24 906) in the general population. There were significant differences (P<0.05) in the ALT failure rate among blood donors based on gender, age, and donation site, but no significant differences (P>0.05) during the blood donation season. There was no statistically significant difference (P>0.05) in the positive rates of four serological markers (HBsAg, anti HCV, HIV Ag/Ab, anti TP) for blood screening pathogens between ALT unqualified and qualified individuals (2.05% vs 1.5%). If the ALT qualification threshold was raised from 50 U/L to 90 U/L, the non qualification rates of male and female blood donors would decrease from 9.82% (2 074/21 125) to 2.23% (471/21 125) and from 2.70% (249/9 216) to 0.75% (69/9 216), respectively. Among the 154 blood donors who donated blood more than 3 times, 88.31% of the 248 ALT test results were in the range of 50-90 U/L. Among them, 9 cases had ALT>130 U/L, and ALT was converted to qualified in subsequent blood donations. [Conclusion] There are differences in the ALT failure rate among blood donors of different genders and ages, and different blood donation sites and operators can also affect the ALT detection values of blood donors. The vast majority of blood donors with ALT failure are caused by transient and non pathological factors. With the widespread use of blood virus nucleic acid testing, appropriately increasing the ALT qualification threshold for blood donors can expand the qualified population and alleviate the shortage of blood sources, and the risk of blood safety will not increase.
5.The Regulatory Mechanisms of Dopamine Homeostasis in Behavioral Functions Under Microgravity
Xin YANG ; Ke LI ; Ran LIU ; Xu-Dong ZHAO ; Hua-Lin WANG ; Lan-Qun MAO ; Li-Juan HOU
Progress in Biochemistry and Biophysics 2025;52(8):2087-2102
As China accelerates its efforts in deep space exploration and long-duration space missions, including the operationalization of the Tiangong Space Station and the development of manned lunar missions, safeguarding astronauts’ physiological and cognitive functions under extreme space conditions becomes a pressing scientific imperative. Among the multifactorial stressors of spaceflight, microgravity emerges as a particularly potent disruptor of neurobehavioral homeostasis. Dopamine (DA) plays a central role in regulating behavior under space microgravity by influencing reward processing, motivation, executive function and sensorimotor integration. Changes in gravity disrupt dopaminergic signaling at multiple levels, leading to impairments in motor coordination, cognitive flexibility, and emotional stability. Microgravity exposure induces a cascade of neurobiological changes that challenge dopaminergic stability at multiple levels: from the transcriptional regulation of DA synthesis enzymes and the excitability of DA neurons, to receptor distribution dynamics and the efficiency of downstream signaling pathways. These changes involve downregulation of tyrosine hydroxylase in the substantia nigra, reduced phosphorylation of DA receptors, and alterations in vesicular monoamine transporter expression, all of which compromise synaptic DA availability. Experimental findings from space analog studies and simulated microgravity models suggest that gravitational unloading alters striatal and mesocorticolimbic DA circuitry, resulting in diminished motor coordination, impaired vestibular compensation, and decreased cognitive flexibility. These alterations not only compromise astronauts’ operational performance but also elevate the risk of mood disturbances and motivational deficits during prolonged missions. The review systematically synthesizes current findings across multiple domains: molecular neurobiology, behavioral neuroscience, and gravitational physiology. It highlights that maintaining DA homeostasis is pivotal in preserving neuroplasticity, particularly within brain regions critical to adaptation, such as the basal ganglia, prefrontal cortex, and cerebellum. The paper also discusses the dual-edged nature of DA plasticity: while adaptive remodeling of synapses and receptor sensitivity can serve as compensatory mechanisms under stress, chronic dopaminergic imbalance may lead to maladaptive outcomes, such as cognitive rigidity and motor dysregulation. Furthermore, we propose a conceptual framework that integrates homeostatic neuroregulation with the demands of space environmental adaptation. By drawing from interdisciplinary research, the review underscores the potential of multiple intervention strategies including pharmacological treatment, nutritional support, neural stimulation techniques, and most importantly, structured physical exercise. Recent rodent studies demonstrate that treadmill exercise upregulates DA transporter expression in the dorsal striatum, enhances tyrosine hydroxylase activity, and increases DA release during cognitive tasks, indicating both protective and restorative effects on dopaminergic networks. Thus, exercise is highlighted as a key approach because of its sustained effects on DA production, receptor function, and brain plasticity, making it a strong candidate for developing effective measures to support astronauts in maintaining cognitive and emotional stability during space missions. In conclusion, the paper not only underscores the centrality of DA homeostasis in space neuroscience but also reflects the authors’ broader academic viewpoint: understanding the neurochemical substrates of behavior under microgravity is fundamental to both space health and terrestrial neuroscience. By bridging basic neurobiology with applied space medicine, this work contributes to the emerging field of gravitational neurobiology and provides a foundation for future research into individualized performance optimization in extreme environments.
6.Relationship Between Gastroesophageal Reflux Disease-Related Symptoms and Clinicopathologic Characteristics and Long-Term Survival of Patients with Esophageal Adenocarcinoma in China
Kan ZHONG ; Xin SONG ; Ran WANG ; Mengxia WEI ; Xueke ZHAO ; Lei MA ; Quanxiao XU ; Jianwei KU ; Lingling LEI ; Wenli HAN ; Ruihua XU ; Jin HUANG ; Zongmin FAN ; Xuena HAN ; Wei GUO ; Xianzeng WANG ; Fuqiang QIN ; Aili LI ; Hong LUO ; Bei LI ; Lidong WANG
Cancer Research on Prevention and Treatment 2025;52(8):661-665
Objective To investigatethe relationship between gastroesophageal reflux disease (GERD) symptoms and clinicopathological characteristics, p53 expression, and survival of Chinese patients with esophageal adenocarcinoma. Methods A total of
7.The role of glucose metabolism reprogramming and its targeted therapeutic agents in inflammation-related diseases
Yi WEI ; Xiao-man JIANG ; Shi-lin XIA ; Jing XU ; Ya LI ; Ran DENG ; Yan WANG ; Hong WU
Acta Pharmaceutica Sinica 2024;59(3):511-519
Cells undergo glucose metabolism reprogramming under the influence of the inflammatory microenvironment, changing their primary mode of energy supply from oxidative phosphorylation to aerobic glycolysis. This process is involved in all stages of inflammation-related diseases development. Glucose metabolism reprogramming not only changes the metabolic pattern of individual cells, but also disrupts the metabolic homeostasis of the body microenvironment, which further promotes aerobic glycolysis and provides favourable conditions for the malignant progression of inflammation-related diseases. The metabolic enzymes, transporter proteins, and metabolites of aerobic glycolysis are all key signalling molecules, and drugs can inhibit aerobic glycolysis by targeting these specific key molecules to exert therapeutic effects. This paper reviews the impact of glucose metabolism reprogramming on the development of inflammation-related diseases such as inflammation-related tumours, rheumatoid arthritis and Alzheimer's disease, and the therapeutic effects of drugs targeting glucose metabolism reprogramming on these diseases.
8.Epidemiological Investigation of Dampness Syndrome Manifestations in the Population at Risk of Cerebrovascular Disease
Xiao-Jia NI ; Hai-Yan HUANG ; Qing SU ; Yao XU ; Ling-Ling LIU ; Zhuo-Ran KUANG ; Yi-Hang LI ; Yi-Kai ZHANG ; Miao-Miao MENG ; Yi-Xin GUO ; Xiao-Bo YANG ; Ye-Feng CAI
Journal of Guangzhou University of Traditional Chinese Medicine 2024;41(3):531-539
Objective To make an epidemiological investigation on traditional Chinese medicine(TCM)dampness syndrome manifestations in the population at risk of cerebrovascular diseases in Guangdong area.Methods A cross-sectional study was conducted to analyze the clinical data related to the risk of cerebrovascular diseases in 330 Guangdong permanent residents.The diagnosis of dampness syndrome,quantitative scoring of dampness syndrome and rating of the risk of stroke were performed for the investigation of the distribution pattern of dampness syndrome and its influencing factors.Results(1)A total of 306(92.73%)study subjects were diagnosed as dampness syndrome.The percentage of dampness syndrome in the risk group was 93.82%(258/275),which was slightly higher than that of the healthy group(48/55,87.27%),but the difference was not statistically significant(χ2 = 2.91,P = 0.112).The quantitative score of dampness syndrome in the risk group was higher than that of the healthy group,and the difference was statistically significance(Z =-2.24,P = 0.025).(2)Among the study subjects at risk of cerebrovascular disease,evaluation time(χ2 = 26.11,P = 0.001),stroke risk grading(χ2= 8.85,P = 0.031),and history of stroke or transient ischemic attack(TIA)(χ2 = 9.28,P = 0.015)were the factors influencing the grading of dampness syndrome in the population at risk of cerebrovascular disease.Conclusion Dampness syndrome is the common TCM syndrome in the population of Guangdong area.The manifestations of dampness syndrome are more obvious in the population with risk factors of cerebrovascular disease,especially in the population at high risk of stroke,and in the population with a history of stroke or TIA.The assessment and intervention of dampness syndrome should be taken into account for future project of stroke prevention in Guangdong.
9.Vitamin D Plays a Crucial Role in Regulating Dopamine Nervous System in Brain
Hua-Lin WANG ; Xu-Dong ZHAO ; Ran LIU ; Ke LI ; Li-Juan HOU
Progress in Biochemistry and Biophysics 2024;51(7):1530-1539
Vitamin D is a unique fat-soluble vitamin that plays an indispensable role in human health. It exists in various forms, the most significant being vitamin D2 (derived from plant sources) and vitamin D3 (synthesized naturally in human skin upon exposure to sunlight). Vitamin D’s primary function is to facilitate the absorption of calcium and phosphorus, which are crucial for maintaining healthy bones. Beyond its role in bone health, vitamin D significantly influences the immune system, muscle function, cardiovascular health, and the regulation of brain functions. A deficiency in vitamin D can lead to various chronic diseases such as rickets, osteoporosis, decreased immunity, increased risk of mental disorders, and cancers. The synthesis of vitamin D in the human body, both peripherally and centrally, relies on sunlight exposure, dietary sources, and various supplements. As a neuroactive steroid, vitamin D impacts both the physiological and pathological processes of the nervous system and plays a key role in brain health. It profoundly affects the brain by regulating neurotransmitter synthesis and maintaining intracellular calcium balance. As an essential chemical molecule, vitamin D participates in complex signal transduction pathways, impacting neurotransmitter functions and synaptic plasticity. Vitamin D’s role in regulating dopamine (DA)—a neurotransmitter critical for motivation, reward perception, and other higher cognitive functions—is particularly noteworthy. Recent studies have revealed that vitamin D not only promotes the synthesis of DA but also plays a role in regulating DA levels within the brain. It exerts neuroprotective effects on DA neurons through anti-inflammatory, antioxidant actions, and neurotrophic support, thereby creating an optimal environment for DA neurons, influencing neuronal structure, and affecting the movement of calcium ions within nerve cells, positively impacting the overall health and functionality of the DA system. Furthermore, vitamin D can regulate the synthesis and release of DA, thus affecting the signal transmission of various DA neural projection pathways in the brain. This function is vital for understanding the complex interactions between neural mechanisms and their effects on key behaviors and cognitive functions. This review aims to delve deeply into the synthesis, metabolism, and pathways of vitamin D’s action, especially its regulatory mechanisms on DA neurons. Through this exploration, this article seeks to provide a solid theoretical foundation and research framework for a deeper understanding of vitamin D’s role in motivation and reward behaviors. This understanding is crucial for appreciating the broader significance of vitamin D in the fields of neuroscience and neurology. In summary, research and discoveries regarding vitamin D’s impact on the nervous system highlight its importance in neural health and function. These insights not only enhance our understanding of the complex workings of the nervous system but also open new avenues for the prevention and treatment of neurological diseases. The exploration of vitamin D’s multifaceted roles offers promising prospects for developing new therapeutic strategies, underscoring the compound’s potential in addressing a range of neural dysfunctions and diseases. As research continues to evolve, the profound implications of vitamin D in the field of neurology and beyond become increasingly apparent, marking it as a key target for ongoing and future scientific inquiry.
10.The Catalytic Mechanism and Activity Modulation of Manganese Superoxide Dismutase
Xu ZHANG ; Lei ZHANG ; Peng-Lin XU ; Tian-Ran LI ; Rui-Qing CHAO ; Zheng-Hao HAN
Progress in Biochemistry and Biophysics 2024;51(1):20-32
Manganese superoxide dismutase catalyzes the dismutation of two molecules of superoxide radicals to one molecule of oxygen and one molecule of hydrogen peroxide. The oxidation of superoxide anion to oxygen by Mn3+SOD proceeds at a rate close to diffusion. The reduction of superoxide anion to hydrogen peroxide by Mn2+SOD can be progressed parallelly in either a fast or a slow cycle pathway. In the slow cycle pathway, Mn2+SOD forms a product inhibitory complex with superoxide anion, which is protonated and then slowly releases hydrogen peroxide out. In the fast cycle pathway, superoxide anion is directly converted into product hydrogen peroxide by Mn2+SOD, which facilitates the revival and turnover of the enzyme. We proposed for the first time that temperature is a key factor that regulates MnSOD into the slow- or fast-cycle catalytic pathway. Normally, the Mn2+ rest in the pent-coordinated state with four amino acid residues (His26, His74, His163 and Asp159) and one water (WAT1) in the active center of MnSOD. The sixth coordinate position on Mn (orange arrow) is open for water (WAT2, green) or O2• to coordinate. With the cold contraction in the active site as temperature decreases, WAT2 is closer to Mn, which may spatially interfere with the entrance of O2• into the inner sphere, and avoid O2•/Mn2+ coordination to reduce product inhibition. Low temperature compels the reaction into the faster outer sphere pathway, resulting in a higher gating ratio for the fast-cycle pathway. As the temperature increases in the physiological temperature range, the slow cycle becomes the mainstream of the whole catalytic reaction, so the increasing temperature in the physiological range inhibits the activity of the enzyme. The biphasic enzymatic kinetic properties of manganese superoxide dismutase can be rationalized by a temperature-dependent coordination model of the conserved active center of the enzyme. When the temperature decreases, a water molecule (or OH-) is close to or even coordinates Mn, which can interfere with the formation of product inhibition. So, the enzymatic reaction occurs mainly in the fast cycle pathway at a lower temperature. Finally, we describe the several chemical modifications of the enzyme, indicating that manganese superoxide dismutase can be rapidly regulated in many patterns (allosteric regulation and chemical modification). These regulatory modulations can rapidly and directly change the activation of the enzyme, and then regulate the balance and fluxes of superoxide anion and hydrogen peroxide in cells. We try to provide a new theory to reveal the physiological role of manganese superoxide dismutase and reactive oxygen species.

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