Tanshinone IIA alleviates pulmonary fibrosis by modulating glutamine metabolic reprogramming based on [U-13C5]-glutamine metabolic flux analysis

INTRODUCTION

Glutamine metabolic reprogramming, mediated by glutaminase (GLS), is an important signal during pulmonary fibrosis (PF) progression. Tanshinone IIA (Tan IIA) is a naturally lipophilic diterpene with antioxidant and antifibrotic properties. However, the potential mechanisms of Tan IIA for regulating glutamine metabolic reprogramming are not yet clear.

OBJECTIVES

This study aimed was to evaluate the role of Tan IIA in intervening in glutamine metabolic reprogramming to exert anti-PF and to explore the potential new mechanisms of metabolic regulation.

METHODS

Fibrotic characteristics was detected via immunofluorescence and western blotting analysis. Cell proliferation was examined with EdU Assay. Cell metabolites were labeled by using stable isotope [U-13C5]-glutamine. By utilizing 100% 13C glutamine tracers and employing network analysis to investigate the activation of metabolic pathways in fibroblasts, as well as evaluating the impact of Tan IIA on these pathways, we accurately quantified the absolute flux of glutaminolysis, proline synthesis, and the TCA cycle pathway using isotopomer network compartmental analysis (INCA), a user-friendly software tool for 13C metabolic flux analysis (13C-MFA). Molecular docking was used for identifying the binding of Tan IIA with target protein.

RESULTS

Tan IIA ameliorate TGF-β1-induced myofibroblast proliferation, reduce collagen I and III and α-SMA protein expression in MRC-5 and NIH-3T3 cells. Furthermore, Tan IIA regulate mitochondrial energy metabolism by modulating TGF-β1-stimulated glutamine metabolic reprogramming in NIH-3T3 cells and inhibiting GLS1 expression, which reduced the metabolic flux of glutamine into mitochondria in myofibroblasts, and also targeted inhibited the expression of Δ1-pyrroline-5-carboxylate synthase (P5CS), P5C reductase 1 (PYCR1), and phosphoserine aminotransferase 1 (PSAT1), and reduced proline hydroxylation and blocked the collagen synthesis pathway.

CONCLUSION

Tan IIA reverses glutamine metabolic reprogramming, reduces mitochondrial energy expenditure, and inhibits collagen matrix synthesis by modulating potential targets in glutamine metabolism. This novel perspective sheds light on the essential role of glutamine metabolic reprogramming in PF.

[Energy metabolism of the immune system : Consequences in chronic inflammation]

BACKGROUND

Energy is the currency of life. The systemic and intracellular energy metabolism plays an essential role for the energy supply of the resting and activated immune system and this also applies to chronic inflammatory diseases.

OBJECTIVE

This presentation examines both components of the systemic and cellular energy metabolism in health and chronic inflammation.

MATERIAL AND METHODS

A literature search was conducted using PubMed, Embase and the Cochrane Library. The information is presented in the form of a narrative review.

RESULTS

A chronically activated immune system acquires large amounts of energy-rich substrates that are lost for other functions of the body. In particular, the immune system and the brain are in competition. The consequences of this competition are many known diseases, such as fatigue, anxiety, depression, anorexia, sleep problems, sarcopenia, osteoporosis, insulin resistance, hypertension and others. The permanent change in the brain causes long-term alterations that stimulate disease sequelae even after disease remission. In the intracellular energy supply, chronic inflammation typically involves a conversion to glycolysis (to lactate, which has its own regulatory functions) and the pentose phosphate pathway in disorders of mitochondrial function. The chronic changes in immune cells of patients with rheumatoid arthritis (RA) lead to a disruption of the citric acid cycle (Krebs cycle). The hypoxic situation in the inflamed tissue stimulates many alterations. A differentiation is made between effector functions and regulatory functions of immune cells.

CONCLUSION

Based on the energy changes mentioned, novel treatment suggestions can be made in addition to those already known in energy metabolism.

Impaired oxygen extraction and adaptation of intracellular energy metabolism in cerebral small vessel disease

BACKGROUND

We aimed to investigate whether combined phosphorous (³¹P) magnetic resonance spectroscopic imaging (MRSI) and quantitative T 2 ' mapping are able to detect alterations of the cerebral oxygen extraction fraction (OEF) and intracellular pH (pH_i) as markers the of cellular energy metabolism in cerebral small vessel disease (SVD).

MATERIALS AND METHODS

32 patients with SVD and 17 age-matched healthy control subjects were examined with 3-dimensional ³¹P MRSI and oxygenation-sensitive quantitative T 2 ' mapping (1/ T 2 '  = 1/T₂* - 1/T₂) at 3 Tesla (T). PH_i was measured within the white matter hyperintensities (WMH) in SVD patients. Quantitative T 2 ' values were averaged across the entire white matter (WM). Furthermore, T 2 ' values were extracted from normal-appearing WM (NAWM) and the WMH and compared between patients and controls.

RESULTS

Quantitative T 2 ' values were significantly increased across the entire WM and in the NAWM in patients compared to control subjects (149.51 ± 16.94 vs. 138.19 ± 12.66 ms and 147.45 ± 18.14 vs. 137.99 ± 12.19 ms, p < 0.05). WM T 2 ' values correlated significantly with the WMH load (ρ=0.441, p = 0.006). Increased T 2 ' was significantly associated with more alkaline pH_i (ρ=0.299, p < 0.05). Both T 2 ' and pH_i were significantly positively correlated with vascular pulsatility in the distal carotid arteries (ρ=0.596, p = 0.001 and ρ=0.452, p = 0.016).

CONCLUSIONS

This exploratory study found evidence of impaired cerebral OEF in SVD, which is associated with intracellular alkalosis as an adaptive mechanism. The employed techniques provide new insights into the pathophysiology of SVD with regard to disease-related consequences on the cellular metabolic state.

Calmodulin complexes with brain and muscle creatine kinase peptides

Calmodulin (CaM) is a ubiquitous Ca2+ sensing protein that binds to and modulates numerous target proteins and enzymes during cellular signaling processes. A large number of CaM-target complexes have been identified and structurally characterized, revealing a wide diversity of CaM-binding modes. A newly identified target is creatine kinase (CK), a central enzyme in cellular energy homeostasis. This study reports two high-resolution X-ray structures, determined to 1.24 ​Å and 1.43 ​Å resolution, of calmodulin in complex with peptides from human brain and muscle CK, respectively. Both complexes adopt a rare extended binding mode with an observed stoichiometry of 1:2 CaM:peptide, confirmed by isothermal titration calorimetry, suggesting that each CaM domain independently binds one CK peptide in a Ca2+-depended manner. While the overall binding mode is similar between the structures with muscle or brain-type CK peptides, the most significant difference is the opposite binding orientation of the peptides in the N-terminal domain. This may extrapolate into distinct binding modes and regulation of the full-length CK isoforms. The structural insights gained in this study strengthen the link between cellular energy homeostasis and Ca2+-mediated cell signaling and may shed light on ways by which cells can 'fine tune' their energy levels to match the spatial and temporal demands.

Role of Sirtuin1-p53 regulatory axis in aging, cancer and cellular reprogramming

Regulatory role of Sirtuin 1 (SIRT1), one of the most extensively studied members of its kind in histone deacetylase family in governing multiple cellular fates, is predominantly linked to p53 activity. SIRT1 deacetylates p53 in a NAD+-dependent manner to inhibit transcription activity of p53, in turn modulate pathways that are implicated in regulation of tissue homoeostasis and many disease states. In this review, we discuss the role of SIRT1-p53 pathway and its regulatory axis in the cellular events which are implicated in cellular aging, cancer and reprogramming. It is noteworthy that these cellular events share few common regulatory pathways, including SIRT1-p53-LDHA-Myc, miR-34a,-Let7 regulatory network, which forms a positive feedback loop that controls cell cycle, metabolism, proliferation, differentiation, epigenetics and many others. In the context of aging, SIRT1 expression is reduced as a protective mechanism against oncogenesis and for maintenance of tissue homeostasis. Interestingly, its activation in aged cells is evidenced in response to DNA damage to protect the cells from p53-dependent apoptosis or senescence, predispose these cells to neoplastic transformation. Importantly, the dual roles of SIRT1-p53 axis in aging and tumourigenesis, either as tumour suppressor or tumour promoter are determined by SIRT1 localisation and type of cells. Conceptualising the distinct similarity between tumorigenesis and cellular reprogramming, this review provides a perspective discussion on involvement of SIRT1 in improving efficiency in the induction and maintenance of pluripotent state. Further research in understanding the role of SIRT1-p53 pathway and their associated regulators and strategies to manipulate this regulatory axis very likely foster the development of therapeutics and strategies for treating cancer and aging-associated degenerative diseases.