Adenylate Kinase 4-A Key Regulator of Proliferation and Metabolic Shift in Human Pulmonary Arterial Smooth Muscle Cells via Akt and HIF-1α Signaling Pathways

Adenylate kinase 4 promotes neuronal energy metabolism and mitophagy in early cerebral ischemia via Parkin/PKM2 pathway

Mitochondrial dysfunction is closely related to brain injury and neurological dysfunction in ischemic stroke. Adenylate kinase 4 (AK4) plays a critical role in energy metabolism and mitochondrial homeostasis. However, the underlying mechanisms remain unclear. In the present study, we demonstrated an important role of AK4 in mitochondrial dysfunction in the early cerebral ischemia. Early focal cerebral ischemia induced decrease of AK4 protein expression in ischemic hemispheric brain tissue in mice. Exposure of cultured primary neuron to oxygen-glucose deprivation (OGD) also induced AK4 downregulation. Overexpression of AK4 in neuron using adeno-associated virus (AAV-AK4) in mice promoted neuronal survival reflected by decreased infarction volume and TUNEL staining. AK4 overexpression inhibited mitochondrial decline and downregulation of energy metabolism-associated proteins (p-AMPK and ATP1A3) induced by MCAO. Moreover, AK4 knock-in using lentivirus carried AK4 vector (LV-AK4) induced energy metabolism shift from glycolysis to oxidation in neuron. Using transmission electron microscope and western blot, we revealed that AK4 overexpression promoted mitophagy and mitophagy-associated proteins expression PINK1 and Parkin after MCAO. Mass spectrometry and co-immunoprecipitation revealed an interaction between AK4 and PKM2. Mechanistically, AK4 indirectly decreased PKM2 expression via enhancing its ubiquitination by increasing the interaction between PKM2 and its ubiquitin E3 ligase Parkin, and inhibits Parkin downregulation. In conclusion, our data demonstrate that AK4/ Parkin /PKM axis prevents cerebral ischemia damage via regulation of neuronal energy metabolism model and mitophagy. AK4 was a new target for intervention of early ischemic neuron injury.

Synthesis, kinetic studies, and QSAR of dinucleoside polyphosphate derivatives as human AK1 inhibitors

Adenylate kinase (AK) plays a crucial role in the metabolic monitoring of cellular adenine nucleotide homeostasis by catalyzing the reversible transfer of a phosphate group between ATP and AMP, yielding two ADP molecules. By regulating the nucleotide levels and energy metabolism, the enzyme is considered a disease modifier and potential therapeutic target for various human diseases, including malignancies and inflammatory and neurodegenerative disorders. However, lacking approved drugs targeting AK hinders broad studies on this enzyme's pathological importance and therapeutic potential. In this work, we determined the effect of a series of dinucleoside polyphosphate derivatives, commercially available (11 compounds) and newly synthesized (8 compounds), on the catalytic activity of human adenylate kinase isoenzyme 1 (hAK1). The tested compounds belonged to the following groups: (1) diadenosine polyphosphates with different phosphate chain lengths, (2) base-modified derivatives, and (3) phosphate-modified derivatives. We found that all the investigated compounds inhibited the catalytic activity of hAK1, yet with different efficiencies. Three dinucleoside polyphosphates showed IC50 values below 1 µM, and the most significant inhibitory effect was observed for P1-(5'-adenosyl) P5-(5'-adenosyl) pentaphosphate (Ap5A). To understand the observed differences in the inhibition efficiency of the tested dinucleoside polyphosphates, the molecular docking of these compounds to hAK1 was performed. Finally, we conducted a quantitative structure-activity relationship (QSAR) analysis to establish a computational prediction model for hAK1 modulators. Two PLS-regression-based models were built using kinetic data obtained from the AK1 activity analysis performed in both directions of the enzymatic reaction. Model 1 (AMP and ATP synthesis) had a good prediction power (R2 = 0.931, Q2 = 0.854, and MAE = 0.286), while Model 2 (ADP synthesis) exhibited a moderate quality (R2 = 0.913, Q2 = 0.848, and MAE = 0.370). These studies can help better understand the interactions between dinucleoside polyphosphates and adenylate kinase to attain more effective and selective inhibitors in the future.

Transcriptional Responses of Different Brain Cell Types to Oxygen Decline

Brain hypoxia is associated with a wide range of physiological and clinical conditions. Although oxygen is an essential constituent of maintaining brain functions, our understanding of how specific brain cell types globally respond and adapt to decreasing oxygen conditions is incomplete. In this study, we exposed mouse primary neurons, astrocytes, and microglia to normoxia and two hypoxic conditions and obtained genome-wide transcriptional profiles of the treated cells. Analysis of differentially expressed genes under conditions of reduced oxygen revealed a canonical hypoxic response shared among different brain cell types. In addition, we observed a higher sensitivity of neurons to oxygen decline, and dissected cell type-specific biological processes affected by hypoxia. Importantly, this study establishes novel gene modules associated with brain cells responding to oxygen deprivation and reveals a state of profound stress incurred by hypoxia.

Mitochondrial influences on smooth muscle phenotype

Smooth muscle cells transition reversibly between contractile and noncontractile phenotypes in response to diverse influences, including many from mitochondria. Numerous molecules including myocardin, procontractile miRNAs, and the mitochondrial protein prohibitin-2 promote contractile differentiation; this is opposed by mitochondrial reactive oxygen species (mtROS), high lactate concentrations, and metabolic reprogramming induced by mitophagy and/or mitochondrial fission. A major pathway through which vascular pathologies such as oncogenic transformation, pulmonary hypertension, and atherosclerosis cause loss of vascular contractility is by enhancing mitophagy and mitochondrial fission with secondary effects on smooth muscle phenotype. Proproliferative miRNAs and the mitochondrial translocase TOMM40 also attenuate contractile differentiation. Hypoxia can initiate loss of contractility by enhancing mtROS and lactate production while simultaneously depressing mitochondrial respiration. Mitochondria can reduce cytosolic calcium by moving it across the inner mitochondrial membrane via the mitochondrial calcium uniporter, and then through mitochondria-associated membranes to and from calcium stores in the sarcoplasmic/endoplasmic reticulum. Through these effects on calcium, mitochondria can influence multiple calcium-sensitive nuclear transcription factors and genes, some of which govern smooth muscle phenotype, and possibly also the production of genomically encoded mitochondrial proteins and miRNAs (mitoMirs) that target the mitochondria. In turn, mitochondria also can influence nuclear transcription and mRNA processing through mitochondrial retrograde signaling, which is currently a topic of intensive investigation. Mitochondria also can signal to adjacent cells by contributing to the content of exosomes. Considering these and other mechanisms, it is becoming increasingly clear that mitochondria contribute significantly to the regulation of smooth muscle phenotype and differentiation.

Intervention of Tanshinone IIA on the PGK1-PDHK1 Pathway to Reprogram Macrophage Phenotype After Myocardial Infarction

BACKGROUND

Myocardial infarction remains a disease with high morbidity and death rate among cardiovascular diseases. Macrophages are abundant immune cells in the heart. Under different stimulatory factors, macrophages can differentiate into different phenotypes and play a dual pro-inflammatory and anti-inflammatory role. Therefore, a potential strategy for the treatment of myocardial infarction is to regulate the energy metabolism of macrophages and thereby regulate the polarization of macrophages. Tan IIA is an effective liposolubility component extracted from the root of Salvia miltiorrhiza and plays an important role in the treatment of cardiovascular diseases. On this basis, this study proposed whether Tan IIA could affect phenotype changes by regulating energy metabolism of macrophages, and thus exert its potential in the treatment of MI.

METHODS

Establishing a myocardial infarction model, Tan IIA was given for 3 days and 7 days for intervention. Cardiac function was detected by echocardiography, and cardiac pathological sections of each group were stained with HE and Masson to observe the inflammatory cell infiltration and fibrosis area after administration. The expression and secretion of inflammatory factors in heart tissue and serum of each group, as well as the proportion of macrophages at the myocardial infarction site, were detected using RT-PCR, ELISA, and immunofluorescence. The mitochondrial function of macrophages was evaluated using JC-1, calcium ion concentration detection, reactive oxygen species detection, and mitochondrial electron microscopic analysis. Mechanically, single-cell transcriptome data mining, cell transcriptome sequencing, and molecular docking technology were used to anchor the target of Tan IIA and enrich the pathways to explore the mechanism of Tan IIA regulating macrophage energy metabolism and phenotype. The target of Tan IIA was further determined by gene knockdown and overexpression assay.

RESULTS

The intervention of Tan IIA can improve the cardiac function, inflammatory cell infiltration and fibrosis after MI, reduce the expression of inflammatory factors in the heart, enhance the secretion of anti-inflammatory factors, increase the proportion of M2-type macrophages, reduce the proportion of M1-type macrophages, and promote tissue repair, suggesting that Tan IIA has pharmacological effects in the treatment of MI. In terms of mechanism, RNA-seq results suggest that the phenotype of macrophages is strongly correlated with energy metabolism, and Tan IIA can regulate the PGK1-PDHK1 signaling pathway, change the energy metabolism mode of macrophages, and then affect its phenotype.

CONCLUSION

Tan IIA regulates the energy metabolism of macrophages and changes its phenotype through the PGK1-PDHK1 signaling pathway, thus playing a role in improving MI.

Exploring the therapeutic mechanisms of Sijunzi decoction in the treatment of sarcopenia: Key targets and signaling pathways

Sarcopenia, an age-associated condition, negatively impacts the quality of life. This study investigates the mechanism of Sijunzi decoction (SJZD), a traditional Chinese formula, against sarcopenia. Active compounds and potential targets of SJZD for sarcopenia were gathered from databases. Hub targets were identified using protein-protein interaction networks, with GO and KEGG analyses suggesting potential pathways. Molecular docking was used to assess compound-target affinity. A lipopolysaccharide-induced sarcopenia rat model was used to verify the targets. Sijunzi decoction contains 92 compounds and 47 targets for sarcopenia. The top 10 hub targets comprise AKT1, ALB, INS, IL6, TNF, TP53, VEGFA, SIRT1, CAT and FOS. GO and KEGG analyses indicate involvement in steroid hormone response, vesicle lumen, receptor agonist activity, and FoxO and HIF-1 signaling pathways. Validation experiments showed that SJZD alleviates sarcopenia by downregulating SIRT1, IL-6, TNF and AKT1. Sijunzi decoction treats sarcopenia by targeting SIRT1, IL-6, TNF and AKT1, potentially involving FoxO and HIF-1 signaling pathways. This highlights SJZD's potential for sarcopenia treatment.

Pulmonary Hypertension: Unveiling Molecular Mechanisms, Diagnosis, and Therapeutic Targets

Pulmonary hypertension (PH) is a progressive and life-threatening disease characterized by increased pulmonary arterial pressure, which leads to right heart hypertrophy and eventually right heart failure [...].

Evidence for Hypoxia-Induced Shift in ATP Production from Glycolysis to Mitochondrial Respiration in Pulmonary Artery Smooth Muscle Cells in Pulmonary Arterial Hypertension

BACKGROUND

The metabolic state of pulmonary artery smooth muscle cells (PASMCs) from patients with pulmonary arterial hypertension (PAH) is not well understood. In this study, we examined the balance between glycolysis and mitochondrial respiration in non-PAH-PASMCs and PAH-PASMCs under normoxia and hypoxia.

METHODS

We investigated the enzymes involved in glycolysis and mitochondrial respiration, and studied the two major energy-yielding pathways (glycolysis and mitochondrial respiration) by measuring extracellular acidification rate (ECAR) and cellular oxygen consumption rate (OCR) using the Seahorse extracellular flux technology.

RESULTS

Under both normoxia and hypoxia, the mRNA and protein levels of pyruvate dehydrogenase kinase 1 and pyruvate dehydrogenase were increased in PAH-PASMCs compared with non-PAH-PASMCs. The mRNA and protein levels of lactate dehydrogenase, as well as the intracellular lactate concentration, were also increased in PAH-PASMCs compared with non-PAH-PASMCs under normoxia. However, these were not significantly increased in PAH-PASMCs compared with non-PAH-PASMCs under hypoxia. Under normoxia, ATP production was significantly lower in PAH-PASMCs (59 ± 5 pmol/min) than in non-PAH-PASMCs (70 ± 10 pmol/min). On the other hand, ATP production was significantly higher in PAH-PASMCs (31 ± 5 pmol/min) than in non-PAH-PASMCs (14 ± 3 pmol/min) under hypoxia.

CONCLUSIONS

There is an underlying change in the metabolic strategy to generate ATP production under the challenge of hypoxia.

Regulation of Adenine Nucleotide Metabolism by Adenylate Kinase Isozymes: Physiological Roles and Diseases

Adenylate kinase (AK) regulates adenine nucleotide metabolism and catalyzes the ATP + AMP ⇌ 2ADP reaction in a wide range of organisms and bacteria. AKs regulate adenine nucleotide ratios in different intracellular compartments and maintain the homeostasis of the intracellular nucleotide metabolism necessary for growth, differentiation, and motility. To date, nine isozymes have been identified and their functions have been analyzed. Moreover, the dynamics of the intracellular energy metabolism, diseases caused by AK mutations, the relationship with carcinogenesis, and circadian rhythms have recently been reported. This article summarizes the current knowledge regarding the physiological roles of AK isozymes in different diseases. In particular, this review focused on the symptoms caused by mutated AK isozymes in humans and phenotypic changes arising from altered gene expression in animal models. The future analysis of intracellular, extracellular, and intercellular energy metabolism with a focus on AK will aid in a wide range of new therapeutic approaches for various diseases, including cancer, lifestyle-related diseases, and aging.

Pulmonary Vascular Remodeling in Pulmonary Hypertension

Pulmonary vascular remodeling is the critical structural alteration and pathological feature in pulmonary hypertension (PH) and involves changes in the intima, media and adventitia. Pulmonary vascular remodeling consists of the proliferation and phenotypic transformation of pulmonary artery endothelial cells (PAECs) and pulmonary artery smooth muscle cells (PASMCs) of the middle membranous pulmonary artery, as well as complex interactions involving external layer pulmonary artery fibroblasts (PAFs) and extracellular matrix (ECM). Inflammatory mechanisms, apoptosis and other factors in the vascular wall are influenced by different mechanisms that likely act in concert to drive disease progression. This article reviews these pathological changes and highlights some pathogenetic mechanisms involved in the remodeling process.

SPOC domain-containing protein 1 regulates the proliferation and apoptosis of human spermatogonial stem cells through adenylate kinase 4

BACKGROUND

Spermatogonial stem cells (SSCs) are the origin of male spermatogenesis, which can reconstruct germ cell lineage in mice. However, the application of SSCs for male fertility restoration is hindered due to the unclear mechanisms of proliferation and self-renewal in humans.

AIM

To investigate the role and mechanism of SPOC domain-containing protein 1 (SPOCD1) in human SSC proliferation.

METHODS

We analyzed publicly available human testis single-cell RNA sequencing (RNA-seq) data and found that SPOCD1 is predominantly expressed in SSCs in the early developmental stages. Small interfering RNA was applied to suppress SPOCD1 expression to detect the impacts of SPOCD1 inhibition on SSC proliferation and apoptosis. Subsequently, we explored the target genes of SPOCD1 using RNA-seq and confirmed their role by restoring the expression of the target genes. In addition, we examined SPOCD1 expression in some non-obstructive azoospermia (NOA) patients to explore the correlation between SPOCD1 and NOA.

RESULTS

The uniform manifold approximation and projection clustering and pseudotime analysis showed that SPOCD1 was highly expressed in the early stages of SSC, and immunohistological results showed that SPOCD1 was mainly localized in glial cell line-derived neurotrophic factor family receptor alpha-1 positive SSCs. SPOCD1 knockdown significantly inhibited cell proliferation and promoted apoptosis. RNA-seq results showed that SPOCD1 knockdown significantly downregulated genes such as adenylate kinase 4 (AK4). Overexpression of AK4 in SPOCD1 knockdown cells partially reversed the phenotypic changes, indicating that AK4 is a functional target gene of SPOCD1. In addition, we found a significant downregulation of SPOCD1 expression in some NOA patients, suggesting that the downregulation of SPOCD1 may be relevant for NOA.

CONCLUSION

Our study broadens the understanding of human SSC fate determination and may offer new theories on the etiology of male infertility.

Association of AK4 Protein From Stem Cell-Derived Neurons With Cognitive Reserve: An Autopsy Study

BACKGROUND AND OBJECTIVES

Identifying protein targets that provide cognitive reserve is a strategy to prevent and treat Alzheimer disease and Alzheimer disease related dementias (AD/ADRD). Previous studies using bulk human brain tissue reported 12 proteins associated with cognitive reserve. This study examined whether the same proteins from induced neurons (iNs) are associated with cognitive reserve of their human donors.

METHODS

Induced pluripotent stem cell (iPSC) lines were generated from cryopreserved peripheral blood mononuclear cells of older adults who were autopsied as part of the Religious Orders Study or Rush Memory and Aging Project. Neurons were induced from iPSCs using a standard neurogenin2 protocol. Tandem mass tag proteomics analyses were conducted on iNs day 21. Cognitive reserve of their human donors was measured as person-specific slopes of cognitive change not accounted for by common neuropathologies.

RESULTS

The 53 human donors died at a mean age of 91 years, all were non-Latino White, and 36 (67.9%) were female. Eighteen were diagnosed with Alzheimer dementia proximate to death, and 34 had pathologic AD diagnosis at autopsy. Approximately 60% of the donors had above-average cognitive reserve such that their cognition declined slower than an average person with comparable burdens of neuropathologies. Eight of the 12 candidate proteins were quantified in iNs proteomics analyses. Higher adenylate kinase 4 (AK4) expression in iNs was associated with lower cognitive reserve, consistent with the previous report for brain AK4 expression.

DISCUSSION

By replicating cortical protein associations with cognitive reserve in human iNs, these data provide a valuable molecular readout for studying complex clinical phenotypes such as cognitive reserve in a dish.

Mitochondrial Regulation of the Hypoxia-Inducible Factor in the Development of Pulmonary Hypertension

Pulmonary hypertension (PH) is a severe progressive lung disorder characterized by pulmonary vasoconstriction and vascular remodeling, culminating in right-sided heart failure and increased mortality. Data from animal models and human subjects demonstrated that hypoxia-inducible factor (HIF)-related signaling is essential in the progression of PH. This review summarizes the regulatory pathways and mechanisms of HIF-mediated signaling, emphasizing the role of mitochondria in HIF regulation and PH pathogenesis. We also try to determine the potential to therapeutically target the components of the HIF system for the management of PH.

IL-13 alleviates idiopathic pulmonary hypertension by inhibiting the proliferation of pulmonary artery smooth muscle cells and regulating macrophage infiltration

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is characterized by medial hypertrophy due to pulmonary artery smooth muscle cell (PASMC) hyperplasia. In the present study, we conducted bioinformatic analyses and cellular experiments to assess the involvement of the interleukin-13 (IL-13) in IPAH.

METHODS

The differentially expressed genes (DEGs) in IPAH and DEGs in IPAH caused by IL-13 treatment were screened using the GEO database. PPI networks were used to analyze the hub genes. Hypoxia-induced PASMCs were treated with IL-13 for in vitro assays. CCK8 and EdU staining were used to observe proliferation of PASMCs, and RT-qPCR was applied to detect the expression of hub genes. The conserved binding sites of microRNAs (miRNAs) in the 3'UTR of hub genes were investigated, and the regulatory relationships of the relevant miRNAs on their targets were verified by RT-qPCR and dual-luciferase assays. The GO and KEGG analyses were performed to study the downstream pathways. The effect of hub genes on immune cell infiltration in IPAH was investigated.

RESULTS

IL-13 altered gene expression in IPAH. IL-13 inhibited the proliferation and the expression of hub genes in PASMCs. The 3'UTR sites between HNRNPA2B1, HNRNPH1, SRSF1, HNRNPU and HNRNPA3 in the hub genes and candidate regulatory miRNAs were well conserved in humans. IL-13-mediated hub genes regulated multiple pathways and influenced immune cell infiltration. Hypoxia-induced PASMCs promoted the M2 polarization of macrophages, whereas IL-13-treated PASMCs skewed the macrophages toward M1 polarization.

CONCLUSIONS

IL-13-mediated alterations in hub genes inhibit PASMC proliferation and promote M1 macrophage infiltration in IPAH.

SPARC, a Novel Regulator of Vascular Cell Function in Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is a life-threatening disease, characterized by excessive pulmonary vascular remodeling, leading to elevated pulmonary arterial pressure and right heart hypertrophy. PH can be caused by chronic hypoxia, leading to hyper-proliferation of pulmonary arterial smooth muscle cells (PASMCs) and apoptosis-resistant pulmonary microvascular endothelial cells (PMVECs). On reexposure to normoxia, chronic hypoxia-induced PH in mice is reversible. In this study, the authors aim to identify novel candidate genes involved in pulmonary vascular remodeling specifically in the pulmonary vasculature.

METHODS

After microarray analysis, the authors assessed the role of SPARC (secreted protein acidic and rich in cysteine) in PH using lung tissue from idiopathic pulmonary arterial hypertension (IPAH) patients, as well as from chronically hypoxic mice. In vitro studies were conducted in primary human PASMCs and PMVECs. In vivo function of SPARC was proven in chronic hypoxia-induced PH in mice by using an adeno-associated virus-mediated Sparc knockdown approach.

RESULTS

C57BL/6J mice were exposed to normoxia, chronic hypoxia, or chronic hypoxia with subsequent reexposure to normoxia for different time points. Microarray analysis of the pulmonary vascular compartment after laser microdissection identified Sparc as one of the genes downregulated at all reoxygenation time points investigated. Intriguingly, SPARC was vice versa upregulated in lungs during development of hypoxia-induced PH in mice as well as in IPAH, although SPARC plasma levels were not elevated in PH. TGF-β1 (transforming growth factor β1) or HIF2A (hypoxia-inducible factor 2A) signaling pathways induced SPARC expression in human PASMCs. In loss of function studies, SPARC silencing enhanced apoptosis and reduced proliferation. In gain of function studies, elevated SPARC levels induced PASMCs, but not PMVECs, proliferation. Coculture and conditioned medium experiments revealed that PMVECs-secreted SPARC acts as a paracrine factor triggering PASMCs proliferation. Contrary to the authors' expectations, in vivo congenital Sparc knockout mice were not protected from hypoxia-induced PH, most probably because of counter-regulatory proproliferative signaling. However, adeno-associated virus-mediated Sparc knockdown in adult mice significantly improved hemodynamic and cardiac function in PH mice.

CONCLUSIONS

This study provides evidence for the involvement of SPARC in the pathogenesis of human PH and chronic hypoxia-induced PH in mice, most likely by affecting vascular cell function.