Limon9
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As Dr. Peat referred to in his newsletters, it's no surprise that a cell-proliferative enzyme activates aerobic glycolysis. Oxidative energy production is halted so the cells may regress to a primitive growth-state. Inhibiting either mTOR or the glycolytic enzyme it upregulated was sufficient to prevent the metabolic derangement and pulmonary fibrosis typically seen in endotoxin challenges and/or sepsis. This study was on the worse end of linguistically-incoherent Chinese studies, so I've corrected the worse errors.
I recall that Ray recommended azithromycin for covid, and it is generally used for other respiratory infections.
Key Points
- in vitro endotoxin treatment of lung fibroblasts increased glycolysis, lactate and collagen synthesis (fibrosis), while decreasing oxidative phosphorylation.
- Treatment of cells with 2-deoxy-d-glucose (a classic glycolysis inhibitor) prevented these effects.
- Inhibition of glycolytic enzyme PFKFB3 with 3PO prevented these effects.
- Inhibition of mTOR (with rapamycin) prevented these effects.
- Pre-treatment of live mice with 3PO before endotoxin injection prevented these effects.
PI3K-Akt-mTOR/PFKFB3 pathway mediated lung fibroblast aerobic glycolysis and collagen synthesis in lipopolysaccharide-induced pulmonary fibrosis.
Lab Invest. 2020 Jun;100(6):801-811. Hu X et al.
Highlights
I recall that Ray recommended azithromycin for covid, and it is generally used for other respiratory infections.
Key Points
- in vitro endotoxin treatment of lung fibroblasts increased glycolysis, lactate and collagen synthesis (fibrosis), while decreasing oxidative phosphorylation.
- Treatment of cells with 2-deoxy-d-glucose (a classic glycolysis inhibitor) prevented these effects.
- Inhibition of glycolytic enzyme PFKFB3 with 3PO prevented these effects.
- Inhibition of mTOR (with rapamycin) prevented these effects.
- Pre-treatment of live mice with 3PO before endotoxin injection prevented these effects.
PI3K-Akt-mTOR/PFKFB3 pathway mediated lung fibroblast aerobic glycolysis and collagen synthesis in lipopolysaccharide-induced pulmonary fibrosis.
Lab Invest. 2020 Jun;100(6):801-811. Hu X et al.
Highlights
"Aerobic glycolysis, which is also known as the “Warburg effect”, oxidizes glucose far more quickly than oxidative phosphorylation, contributing to an increased production of lactate [7] and plays a major role in various diseases. Reportedly, aerobic glycolysis in lung tissues also plays a crucial role during pulmonary fibrosis [8–10] and LPS-induced sepsis [11]. However, whether LPS could directly induce aerobic glycolysis and collagen synthesis in lung fibroblasts remains unclear."
"Our previous study revealed that LPS induces proliferation and activation of lung fibroblasts via the phosphatidylinositol3-kinase-protein kinase B-mammalian target of rapamycin (PI3K-Akt-mTOR) pathway [12, 13]. Other studies also showed that PI3K-Akt-mTOR pathway activation was involved in the regulation of cellular aerobic glycolysis [14, 15], which is further associated with the expression and activation of the key enzyme 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3) [16]."
"To investigate the effects of aerobic glycolysis on LPS-induced collagen synthesis in lung fibroblasts, 2-DG, an inhibitor of aerobic glycolysis, was applied. MRC-5 cells were treated with LPS (1 μg/mL) for 48 h. We used ECAR [extracellular acidification rate] to measure lactate production, a representation of the glycolytic rate. Compared with the control group, LPS treatment led to the continuous growth of ECAR in the lung fibroblasts, indicating enhanced glycolysis of the cells. OCR [oxygen consumption rate], a surrogate for mitochondrial respiratory activity, decreased after LPS treatment, which indicated a transition from oxidative phosphorylation to aerobic glycolysis in lung fibroblasts, and these effects were inhibited by 2-DG treatment (Fig. 1a, b). Furthermore, lactate, the end product of aerobic glycolysis, also increased after LPS treatment and could be inhibited by 2-DG pretreatment (Fig. 1c). 2-DG pretreatment also prevented the LPS-induced increased expression of collagen I (Fig. 1d). These findings indicated that aerobic glycolysis could mediate LPS-induced collagen synthesis in the lung fibroblasts in vitro."
"To investigate whether PFKFB3 is essential in LPS-induced collagen synthesis in lung fibroblasts, we first used 3PO, a selective inhibitor of PFKFB3. As shown in Fig. 2a, the pretreatment with 3PO significantly decreased the PFKFB3 level. Furthermore, pretreatment with 3PO inhibited the aerobic glycolysis in the lung fibroblasts as indicated by the lower levels of ECAR, higher levels of OCR, and less production of lactate (Fig. 2b–d), as well as inhibited lung fibroblasts collagen synthesis (Fig. 2e)."
"As shown in Fig. 4a, b, LPS promoted the activation of the PI3K-Akt-mTOR pathway detected by the phosphorylation of Akt (p-Akt) and mTOR (p-mTOR) as well as the expression of PFKFB3 at 6 h after LPS treatment, which could be inhibited by application of PI3K-Akt inhibitor LY294002, and mTOR inhibitor rapamycin, respectively. Futhermore, this inhibition precluded the LPS-induced aerobic glycolysis and collagen synthesis in the lung fibroblasts as indicated by the decreased levels of ECAR (Fig. 4c), elevated levels of OCR (Fig. 4d), less lactate production (Fig. 4e, f), and downregulation of the expression of collagen I (Fig. 4g, h). Therefore, we speculated that inhibition of the PI3K-Akt-mTOR pathway precludes LPS-induced PFKFB3 expression as well as aerobic glycolysis and collagen synthesis in the lung fibroblasts."
". . . mice were intraperitoneally pretreated with 3PO (70 mg/kg) followed by LPS (5 mg/kg) or the same dose of saline injection for 5 consecutive days. We found that the survival rate of each group were 100%, 100%, 75%, and 90% (control, 3PO, LPS, 3PO + LPS), respectively. To fully clarify the effect of 3PO on LPS-induced pulmonary fibrosis model, HE and Masson staining were performed at 3, 7, 14, and 28 days after LPS treatment and we found that mild pulmonary fibrosis was observed at 3, 7, and 14 days after LPS treatment, and typical pulmonary fibrosis was detected at 28 days, which could be reversed by 3PO pretreatment (Fig. S1A,B)."
". . . aerobic glycolysis, first detected by Warburg, suggested that tumor cells also initiate aerobic glycolysis [what about the other way round!] to produce lactate under aerobic conditions, which in turn, promotes the proliferation of the cells [22, 23]. Recent studies have shown that not only in tumor cells, aerobic glycolysis also exhibits and plays an important role in many diseases [24], such as sepsis [25, 26] and pulmonary fibrosis [21]. Also, LPS stimulates aerobic glycolysis in macrophages raises the level of lactate [25]."
"PFKFB3 is one of the critical glycolytic enzymes that regulate the synthesis of fructose-2, 6-bisphosphate (Fru2, 6-BP), which is the potent allosteric activator of glycolytic rate-limiting enzyme 6-phosphate fructose kinase 1 (6-phosphofructo-1-kinase, PFK-1). This enzyme converts fructose-6-phosphate (F6P) into fructose-1, 6bisphosphate (Fru-1, 6-BP), and plays a key role in glycolysis [28]. Therefore, the expression and activation states of PFKFB3 are directly related to the initiation of aerobic glycolysis. It was reported that in pulmonary fibrosis, the expression of PFKFB3 is upregulated in lung tissues [21]. However, its function has not yet been clarified in LPS-induced pulmonary fibrosis. The current data confirmed that LPS upregulates the expression of PFKFB3 in both lung fibroblasts and fibrotic lungs while inhibiting the level of PFKFB3 with the pretreatment of 3PO or PFKFB3 shRNA precludes the LPS-induced aerobic glycolysis and pulmonary fibrosis. Thus, it can be speculated that PFKFB3 plays a key role in regulating LPS-induced aerobic glycolysis and pulmonary fibrosis."
"Our previous study showed that LPS induces the proliferation and activation of lung fibroblasts through the activation of PI3K-Akt-mTOR pathway [12, 29]. As a significant signaling pathway, the activated PI3K-AktmTOR pathway plays a crucial role in the initiation of glycolysis [14], activation of cell proliferation [15, 30], as well as the occurrence of pulmonary fibrosis [15, 31]. It was reported that PFKFB3 could be upregulated by mTOR [32], and the PI3K-Akt-mTOR pathway was reported to be involved in the expression of PFKFB3 in liver [33]. This study confirmed that LPS activates the PI3K-Akt-mTOR pathway accompanied by the upregulation of PFKFB3 and aerobic glycolysis in the lung fibroblasts, which could be rescued by using PI3K-Akt-mTOR selective inhibitors, LY294002, and rapamycin, respectively."
"Taken together, the current study revealed that the PI3KAkt-mTOR/PFKFB3 pathway mediates aerobic glycolysis in the lung fibroblasts during LPS-induced pulmonary fibrosis, and intervention of the activation of the PI3K-AktmTOR/PFKFB3 pathway to regulate the metabolism of lung fibroblasts could be an effective therapeutic target for LPS-induced pulmonary fibrosis. In conclusion, this study demonstrated that LPS promotes collagen synthesis in the lung fibroblasts through aerobic glycolysis via activation of the PI3K-Akt-mTOR/ PFKFB3 pathway in LPS-induced pulmonary fibrosis."