L-Arginine, as an essential amino acid, is a potential substitute for treating COPD via regulation of ROS/NLRP3/NF-κB signaling pathway

Targeting reprogrammed metabolism as a therapeutic approach for respiratory diseases

Metabolic reprogramming underlies the etiology and pathophysiology of respiratory diseases such as asthma, idiopathic pulmonary fibrosis (IPF), and chronic obstructive pulmonary disease (COPD). The dysregulated cellular activities driving airway inflammation and remodelling in these diseases have reportedly been linked to aberrant shifts in energy-producing metabolic pathways: glycolysis and oxidative phosphorylation (OXPHOS). The rewiring of glycolysis and OXPHOS accompanying the therapeutic effects of many clinical compounds and natural products in asthma, IPF, and COPD, supports targeting metabolism as a therapeutic approach for respiratory diseases. Correspondingly, inhibiting glycolysis has largely attested effective against experimental asthma, IPF, and COPD. However, modulating OXPHOS and its supporting catabolic pathways like mitochondrial pyruvate catabolism, fatty acid β-oxidation (FAO), and glutaminolysis for these respiratory diseases remain inconclusive. An emerging repertoire of metabolic enzymes are also interconnected to these canonical metabolic pathways that similarly possess therapeutic potential for respiratory diseases. Taken together, this review highlights the urgent demand for future studies to ascertain the role of OXPHOS in different respiratory diseases, under different stimulatory conditions, and in different cell types. While this review provides strong experimental evidence in support of the inhibition of glycolysis for asthma, IPF, and COPD, further verification by clinical trials is definitely required.

L-arginine mitigates bleomycin-induced pulmonary fibrosis in rats through regulation of HO-1/PPAR-γ/β-catenin axis

Pulmonary fibrosis is a chronic and progressively deteriorating lung condition that can be replicated in laboratory animals by administering bleomycin, a chemotherapeutic antibiotic known for its lung fibrosis-inducing side effects. L-arginine, a semi-essential amino acid, is recognized for its diverse biological functions, including its potential to counteract fibrosis. This study aimed to evaluate the antifibrotic properties of L-arginine on bleomycin-induced pulmonary fibrosis in rats. The administration of a single intratracheal dose of bleomycin resulted in visible and microscopic damage to lung tissues, an uptick in oxidative stress markers, and an elevation in inflammatory, apoptotic, and fibrotic indicators. A seven-day treatment with L-arginine post-bleomycin exposure markedly improved the gross and histological architecture of the lungs, prevented the rise of malondialdehyde and carbonyl content, and enhanced total antioxidant capacity alongside the activities of antioxidant enzymes. Also, L-arginine attenuated the expression of the pro-fibrotic factors, transforming growth factor-β and lactate dehydrogenase in bronchoalveolar lavage fluid. In the lung tissue, L-arginine reduced collagen deposition, hydroxyproline concentration, and mucus production, along with decreasing expression of α-smooth muscle actin, tumor necrosis factor-α, caspase-3, matrix metalloproteinase-9, and β-catenin. Moreover, it boosted levels of nitric oxide and upregulated the expression of peroxisome proliferator-activated receptor-γ (PPAR-γ), heme oxygenase-1 (HO-1), and E-cadherin and downregulating the expression of β-catenin. These findings suggest that L-arginine has preventive activities against bleomycin-induced pulmonary fibrosis. This effect can be attributed to the increased production of nitric oxide, which modulates the HO-1/PPAR-γ/β-catenin axis.

Biological importance of arginine: A comprehensive review of the roles in structure, disorder, and functionality of peptides and proteins

Arginine shows Jekyll and Hyde behavior in several respects. It participates in protein folding via ionic and H-bonds and cation-pi interactions; the charge and hydrophobicity of its side chain make it a disorder-promoting amino acid. Its methylation in histones; RNA binding proteins; chaperones regulates several cellular processes. The arginine-centric modifications are important in oncogenesis and as biomarkers in several cardiovascular diseases. The cross-links involving arginine in collagen and cornea are involved in pathogenesis of tissues but have also been useful in tissue engineering and wound-dressing materials. Arginine is a part of active site of several enzymes such as GTPases, peroxidases, and sulfotransferases. Its metabolic importance is obvious as it is involved in production of urea, NO, ornithine and citrulline. It can form unusual functional structures such as molecular tweezers in vitro and sprockets which engage DNA chains as part of histones in vivo. It has been used in design of cell-penetrating peptides as drugs. Arginine has been used as an excipient in both solid and injectable drug formulations; its role in suppressing opalescence due to liquid-liquid phase separation is particularly very promising. It has been known as a suppressor of protein aggregation during protein refolding. It has proved its usefulness in protein bioseparation processes like ion-exchange, hydrophobic and affinity chromatographies. Arginine is an amino acid, whose importance in biological sciences and biotechnology continues to grow in diverse ways.

Expression Profiles of circRNAs and Identification of hsa_circ_0007608 and hsa_circ_0064656 as Potential Biomarkers for COPD-PH Patients

Introduction

Pulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD), which can worsen the prognosis and increase the mortality of COPD patients. Circular RNA (circRNA) has been discovered to participate in the occurrence and progression of PH in COPD and may have significant prospects for advanced diagnostics and prognosis evaluation. However, the expression profile of circRNAs in human lung tissues with definite diagnosis of COPD-PH remains to be further explored and validated.

Methods

Twelve human lung tissue samples (6 each from COPD-PH and control groups) were collected and subjected to high-throughput sequencing. QRT-PCR was performed to validate the differential expression levels of the top 10 dysregulated circRNAs in patients' plasma samples, HPAECs and HPASMCs. Functional and pathway enrichment analysis on target genes was performed to explore the potential functions and pathways of those circRNAs. Hub genes obtained after conducting bioinformatics analysis on the predicted target mRNAs were verified by qRT-PCR in HPAECs and HPASMCs, and then we selected VCAN as a potential key gene involved in the pathogenesis of COPD-PH for immunohistochemistry validation in lung tissue.

Results

A total of 136 circRNAs (39 up-regulated and 97 down-regulated) were differentially expressed between the two groups. Following qRT-PCR validation, two circRNAs (hsa_circ_0007608 and hsa_circ_0064656) were believed to be involved in the pathogenesis. GO and KEGG pathway analysis suggested that these two DECs were mainly related to the celluar proliferation, migration and EndMT. PPI network revealed 11 pairs of key mRNAs. VCAM1, VCAN and THBS1, three hub mRNAs with the highest reliability among all, were validated and proven to be up-regulated in COPD-PH. We innovatively found that VCAN may be involved in COPD-PH.

Conclusion

This study identified the functional circRNAs, providing insights into the molecular mechanisms and predictions of COPD-PH, and may provide potential diagnostic biomarkers or therapeutic targets for COPD-PH.