bims-mecmid 2022-03-13 papers

bims-mecmid

Biomed News

on Membrane communication in mitochondrial dynamics

Issue of 2022–03–13
six papers selected by
Mauricio Cardenas Rodriguez, University of Padova

RIP1 Regulates Mitochondrial Fission during Skeletal Muscle Ischemia Reperfusion Injury.
[Effects of vibration on the expression of mitochondrial fusion and fission genes and ultrastructure of skeletal muscle in rabbits].
Alterations in hippocampal mitochondrial dynamics are associated with neurodegeneration and recognition memory decline in old male mice.
Irisin alleviates vascular calcification by inhibiting VSMC osteoblastic transformation and mitochondria dysfunction via AMPK/Drp1 signaling pathway in chronic kidney disease.
Changes in the Mitochondrial Dynamics and Functions Together with the mRNA/miRNA Network in the Heart Tissue Contribute to Hypoxia Adaptation in Tibetan Sheep.
Effects of proton pumping on the structural rigidity of cristae in mitochondria.

J Invest Surg. 2022 Mar 06. 1-6

RIP1 Regulates Mitochondrial Fission during Skeletal Muscle Ischemia Reperfusion Injury.

Yu Cao, Shunli Chen, Xiangqing Xiong, Lina Lin, Wantie Wang, Liangrong Wang.

   BACKGROUND: Dynamin related protein-1 (Drp1)-mediated mitochondrial fission relates to ischemia reperfusion (IR) injury, and its association with necroptosis is implied. We hypothesized that receptor-interacting protein 1 (RIP1), a key kinase in necroptosis, acted as an upstream of Drp1-mediated mitochondrial fission during skeletal muscle IR.
METHODS: Thirty rats were randomized into the SM, IR, NI, MI, and DI group (n = 6). The rats in the SM group were shamly operated, and those in the IR group were subjected to 4-hour ischemia of the right hindlimb that was followed by 4-hour reperfusion. Intraperitoneal administration of Nec-1 1 mg/kg, Mdivi-1 1.2 mg/kg and same volume of DMSO were given before ischemia in the NI, MI and DI groups, respectively. Upon reperfusion, the soleus muscles were harvested to determine morphological changes and the expression of RIP1, total Drp1 and p-Drp1 (Ser616). Moreover, the muscular oxidative stress indicators and plasma muscle damage biomarkers were detected.
RESULTS: IR led to impaired histopathological structures and mitochondrial fragmentation in the soleus muscle tissue, accompanied with increased muscular oxidative stress and muscle injury biomarkers, which could be similarly alleviated by Mdivi-1 and Nec-1 (p < 0.05). RIP1 and p-Drp1 (Ser616) protein levels were significantly upregulated in the soleus muscle subjected to IR injury, this upregulation was attenuated in the NI group, and Mdivi-1 downregulated the protein expression of p-Drp1 (Ser616) but not of RIP1 (p < 0.05).
CONCLUSION: RIP1 functions as an upstream of Drp1-mediated mitochondrial fission in the execution of necroptosis during skeletal muscle IR.

Keywords:  Reperfusion injury; dynamin related protein-1; mitochondrial fission; necroptosis; receptor-interacting protein 1; skeletal muscle

DOI:  https://doi.org/10.1080/08941939.2022.2036880
Zhonghua Lao Dong Wei Sheng Zhi Ye Bing Za Zhi. 2022 Jan 20. 40(1): 18-23

[Effects of vibration on the expression of mitochondrial fusion and fission genes and ultrastructure of skeletal muscle in rabbits].

J X Li, S Y Xie, Z Q Zhang, C Z Zhang, L Lin.

  Objective: To study the effects of vibration on the expression of mitochondrial fusion and fission genes and ultrastructure of skeletal muscle in rabbits. Methods: Thirty-two 3.5-month-old New Zealand rabbits were randomly divided into low-intensity group, medium-intensity group, high-intensity group and control group, with 8 rabbits in each group. The rabbits in the experimental group were subjected to hind limb vibration load test for 45 days. The vibration intensity of the high intensity group was 12.26 m/s(2), the medium intensity group was 6.13 m/s(2), and the low intensity group was 3.02 m/s(2) according to the effective value of weighted acceleration[a(hw (4))] for 4 hours of equal energy frequency. The control group was exposed to noise only in the same experimental environment as the medium-intensity group. The noise levels of each group were measured during the vibration load experiment. After the test, the mRNA expression of mitochondrial fusion gene (Mfn1/Mfn2) and fission gene (Fis1, Drp1) by RT-PCR in the skeletal muscles were measured and the ultrastructure of the skeletal muscles were observed in high intensity group. Results: The mRNA expression of mitochondrial in the skeletal muscle tissues of control group, low intensity group, medium intensity group and high intensity group were Mfn1: 3.25±1.36, 3.85±1.90, 4.53±2.31 and 11.63±7.68; Mfn2: 0.68±0.25, 1.02±0.40, 0.94±0.33 and 1.40±0.45; Fis1: 1.05±0.62, 1.15±0.59, 1.53±1.06 and 2.46±1.51 and Drp1: 3.72±1.76, 2.91±1.63, 3.27±2.01 and 4.21±2.46, respectively. Compared with the control group, the expressions of Mfn1 mRNA, Mfn2 mRNA and Fis1 mRNA in the high-intensity group increased significantly (P<0.05) , and the expressions of Mfn2 mRNA in the medium-intensity group and the low-intensity group increased significantly (P<0.05) . Compared with the control group, the ultrastructure of skeletal muscle of high intensity group showed mitochondrial focal accumulation, cristae membrane damage, vacuole-like changes; Z-line irregularity of muscle fibers, and deficiency of sarcomere. Conclusion: Vibration must be lead to the abnormal mitochondrial morphology and structure and the disorder of energy metabolism due to the expression imbalance of mitochondrial fusion and fission genes in skeletal muscles of rabbits, which may be an important target of vibration-induced skeletal muscle injury.

Keywords:  Mitochondrial fusion and fission genes; Rabbit; Skeletal muscle; Ultrastructure; Vibration

DOI:  https://doi.org/10.3760/cma.j.cn121094-20201103-00608
Biogerontology. 2022 Mar 09.

Alterations in hippocampal mitochondrial dynamics are associated with neurodegeneration and recognition memory decline in old male mice.

Ela Mishra, Mahendra Kumar Thakur.

  Mitochondrial dynamics is a key process that modulates the ultrastructure, quality and function of mitochondria. It is disrupted in numerous major neurodegenerative disorders including Parkinson's, Alzheimer's and Huntington's disease. Mitochondrial dysfunction has been correlated with the loss of memory. Previous studies suggest the involvement of Vdac1 and Drp1 in outer mitochondrial membrane permeabilization and promotion of mitochondrial fragmentation through Drp1 phosphorylation at S616. However, alterations in mitochondrial dynamics with respect to aging, memory loss and neurodegeneration remain unexplored. Therefore, the present study focuses on the involvement of mitochondrial dynamics in neurodegeneration and recognition memory decline during aging. The recognition memory decline was validated by the novel object recognition test and measurement of hippocampal Arc protein level during aging. The ultrastructure analysis revealed a decline in mitochondrial length and area, while an increase in the number of fragmented, round and disrupted mitochondria in the hippocampus during aging. Disruption was also evident in mitochondrial cristae and membrane with advancing age. The change in mitochondrial morphology was corroborated by an increase in the expression of phospho-Drp1 (S616) and Cyt-c proteins but decline in Mfn2, LC3B, Vdac1, Bcl-XL and Bcl-2 proteins in the hippocampus during aging. Taken together, our findings reveal that an increase in the expression of phospho-Drp1 (S616) and decrease in Mfn2 and LC3B proteins in the hippocampus bring about a reduction in mitochondrial length and area, and rise in mitochondrial fragmentation leading to reduced neuronal cell density, increased neurodegeneration and recognition memory decline in old male mice. Diagram depicts the increase in hippocampal mitochondrial fragmentation during aging of mice. Increased mitochondrial fragmentation causes distorted mitochondrial function such as decrease in ATP/ADP transportation due to decrease in Vdac1 protein level and increase in oxidative damage. These alterations result in hippocampal neurodegeneration and consequently impairment in recognition memory during aging.

Keywords:  Aging; Apoptosis; Hippocampus; Mitochondrial dynamics; Neurodegeneration; Recognition memory

DOI:  https://doi.org/10.1007/s10522-022-09960-3
Atherosclerosis. 2022 Feb 16. pii: S0021-9150(22)00076-4. [Epub ahead of print]346 36-45

Irisin alleviates vascular calcification by inhibiting VSMC osteoblastic transformation and mitochondria dysfunction via AMPK/Drp1 signaling pathway in chronic kidney disease.

Pei-Wen Wang, Qi Pang, Ting Zhou, Xin-Yu Song, Ya-Jing Pan, Lin-Pei Jia, Ai-Hua Zhang.

   BACKGROUND AND AIMS: Vascular calcification (VC) is an intricate active process, significantly controlled by vascular smooth muscle cells (VSMCs). Mitochondrial dysfunction plays a pivotal role in VC and VSMCs osteoblastic transformation. We previously reported that decreased levels of Irisin were independently associated with VC in hemodialysis patients. The present study aimed to investigate the role of Irisin in VC, especially in VSMCs osteoblastic transformation and mitochondrial function.
METHODS: In vitro, VSMCs calcification was induced by β-glycerophosphate, while in vivo VC was triggered by adenine and high phosphorus diet. Alizarin red, Von Kossa staining, and calcium and Alp activity were performed to test VC. Western blot and immunohistochemical staining were employed to analyze the expression of proteins associated with VSMCs osteoblastic transformation and AMPK signaling. Mitochondrial membrane potential (MMP) and structures were observed by immunofluorescence staining.
RESULTS: Irisin alleviated VSMCs calcification induced by β-glycerophosphate. Mechanistically, Irisin activated AMPK and downregulated the expression of Drp1, further alleviating mitochondria fission and VSMCs osteoblastic transformation. In vivo, Irisin decreased serum creatinine, urea and phosphorous levels in chronic kidney disease (CKD) mice. Importantly, Irisin treatment postponed CKD-associated VC with the upregulation of α-Sma and p-AMPK expression, and the downregulation of Runx2 and Drp1 expression.
CONCLUSIONS: Our results firstly reveal that Irisin inhibits CKD-associated VC. Irisin suppresses VSMCs osteoblastic transformation and mitochondria dysfunction via AMPK/Drp1 signaling.

Keywords:  Chronic kidney disease; Irisin; Mitochondrial fission; Osteoblastic transformation; Vascular calcification

DOI:  https://doi.org/10.1016/j.atherosclerosis.2022.02.007
Animals (Basel). 2022 Feb 25. pii: 583. [Epub ahead of print]12(5):

Changes in the Mitochondrial Dynamics and Functions Together with the mRNA/miRNA Network in the Heart Tissue Contribute to Hypoxia Adaptation in Tibetan Sheep.

Yuliang Wen, Shaobin Li, Fangfang Zhao, Jiqing Wang, Xiu Liu, Jiang Hu, Gaoliang Bao, Yuzhu Luo.

  This study aimed to provide insights into molecular regulation and mitochondrial functionality under hypoxia by exploring the mechanism of adaptation to hypoxia, blood indexes, tissue morphology, mRNA/miRNA regulation, mitochondrial dynamics, and functional changes in Tibetan sheep raised at different altitudes. With regard to blood indexes and myocardial morphology, the HGB, HCT, CK, CK-MB, LDH, LDH1, SOD, GPX, LDL level, and myocardial capillary density were significantly increased in the sheep at higher altitudes (p < 0.05). The RNA-seq results suggested the DEmRNAs and DEmiRNAs are mainly associated with the PI3K-Akt, Wnt, and PPAR signaling pathways and with an upregulation of oncogenes (CCKBR, GSTT1, ARID5B) and tumor suppressor factors (TPT1, EXTL1, ITPRIP) to enhance the cellular metabolism and increased ATP production. Analyzing mRNA-miRNA coregulation indicated the mitochondrial dynamics and functions to be significantly enriched. By analyzing mitochondrial dynamics, mitochondrial fusion was shown to be significantly increased and fission significantly decreased in the heart with increasing altitude (p < 0.05). There was a significant increase in the density of the mitochondria, and a significant decrease in the average area, aspect ratio, number, and width of single mitochondrial cristae with increasing altitudes (p < 0.05). There was a significant increase in the NADH, NAD+ and ATP content, NADH/NAD+ ratio, and CO activity, while there was a significant decrease in SDH and CA activity in various tissues with increasing altitudes (p < 0.05). Accordingly, changes in the blood indexes and myocardial morphology of the Tibetan sheep were found to improve the efficiency of hemoglobin-carrying oxygen and reduce oxidative stress. The high expression of oncogenes and tumor suppressor factors might facilitate cell division and energy exchange, as was evident from enhanced mitochondrial fission and OXPHOS expression; however, it reduced the fusion and TCA cycle for the further rapid production of ATP in adaptation to hypoxia stress. This systematic study has for the first time delineated the mechanism of hypoxia adaptation in the heart of Tibetan sheep, which is significant for improving the ability of the mammals to adapt to hypoxia and for studying the dynamic regulation of mitochondria during hypoxia conditions.

Keywords:  Qinghai–Tibet Plateau; RNA-seq; Tibetan sheep; dynamics; hypoxia; mitochondria; oxidative phosphorylation

DOI:  https://doi.org/10.3390/ani12050583
Arch Biochem Biophys. 2022 Mar 08. pii: S0003-9861(22)00057-1. [Epub ahead of print] 109172

Effects of proton pumping on the structural rigidity of cristae in mitochondria.

Mayu Yoneda, Jannatul Aklima, Ikuroh Ohsawa, Yoshihiro Ohta.

  Mitochondria change their morphology and inner membrane structure depending on their activity. Since mitochondrial activity also depends on their structure, it is important to elucidate the interrelationship between the activity and structure of mitochondria. However, the mechanism by which mitochondrial activity affects the structure of cristae, the folded structure of the inner membrane, is not well understood. In this study, the effect of the mitochondrial activity on the cristae structure was investigated by examining the structural rigidity of cristae. Taking advantage of the fact that unfolding of cristae induces mitochondrial swelling, we investigated the relationship between mitochondrial activity and the susceptibility to swelling. The swelling of individual isolated mitochondria exposed to a hypotonic solution was observed with an optical microscope. The presence of respiratory substrates (malate and glutamate) increased the percentage of mitochondria that underwent swelling, and the further addition of rotenone or KCN (inhibitors of proton pumps) reversed the increase. In the absence of respiratory substrates, acidification of the buffer surrounding the mitochondria also increased the percentage of swollen mitochondria. These observations suggest that acidification of the outer surface of inner membranes, especially intracristal space, by proton translocation from the matrix to the intracristal space, decreases the structural rigidity of the cristae. This interpretation was verified by the observation that ADP or CCCP, which induces proton re-entry to the matrix, suppressed the mitochondrial swelling in the presence of respiratory substrates. The addition of CCCP to the cells induced a morphological change in mitochondria from an initial elongated structure to a largely curved structure at pH 7.4, but there were no morphological changes when the pH of the cytosol dropped to 6.2. These results suggest that a low pH in the intracristal space may be helpful in maintaining the elongated structure of mitochondria. The present study shows that proton pumping by the electron transfer chain is the mechanism underlying mitochondrial morphology and the flexibility of cristae structure.

Keywords:  Inner mitochondrial membrane; Intracristal space; Proton pumps; mitochondria; mitochondrial cristae; mitochondrial swelling

DOI:  https://doi.org/10.1016/j.abb.2022.109172