PP2Ac upregulates PI3K-Akt signaling and induces hepatocyte apoptosis in liver donor after brain death

Glucose deprivation-restoration induces labile iron overload and ferroptosis in renal tubules through V-ATPase-mTOR axis-mediated ferritinophagy and iron release by TPC2

Renal ischemia-reperfusion injury (IRI), a common complication following kidney transplantation and partial nephrectomy, is the leading cause of renal dysfunction with limited treatment. Excessive cellular iron accumulation drives lipid peroxidation and activates pathways associated with ferroptosis, which has been implicated in renal IRI. However, the regulatory mechanisms of cellular iron metabolism and its relationship with ferroptosis during ischemia-reperfusion (IR) remain unclear. In this study, in vitro OGSD-R (oxygen, glucose, and serum deprivation-restoration) models and in vivo IR models were employed to investigate alterations in iron metabolism, ferroptosis, and the underlying molecular mechanisms using immunofluorescence, immunoblotting and biochemical testing. We identified glucose deprivation-restoration (GD-R) as a key trigger of cellular iron overload under renal IR condition. Mechanistically, GD-R-induced iron overload is driven by the dysfunction of vacuolar ATPase (V-ATPase)-mammalian target of rapamycin (mTOR) pathway. Inactivation of mTOR results in lysosomal iron releases via two-pore channel 2 (TPC2) and ferritin degradation through ferritinophagy. This process elevates intracellular iron levels, thereby promoting ferroptosis in renal IRI. Targeting cellular iron metabolism effectively alleviates renal IRI. These findings highlight the critical role of glucose metabolism and V-ATPase-mTOR pathway in the regulation of iron homeostasis and ferroptosis during renal IRI, and establish a mechanistic link among glucose metabolism, iron overload and ferroptosis, providing potential therapeutic targets for renal IRI.

Inflammatory Microenvironment-Responsive Microsphere Vehicles Modulating Gut Microbiota and Intestinal Inflammation for Intestinal Stem Cell Niche Remodeling in Inflammatory Bowel Disease

Intestinal stem cells (ISCs) engage in proliferation to maintain a stable stem cell population and differentiate into functional epithelial subpopulations. This intricate process is upheld by various signals derived from the host and gut microbiota, establishing an ISC niche. However, during inflammatory bowel disease (IBD), this signaling niche undergoes dramatic changes, leading to impaired ISC and hindered restoration of the damaged intestinal epithelial barrier. This study introduces intestinal inflammatory microenvironment-responsive microsphere vehicles designed to remodel the ISC niche, offering an approach to treat IBD. Using an advanced emulsion technique, these microsphere vehicles specifically target colonic inflammation sites, delivering a responsive release of MXene and l-arginine. This delivery system is formulated to modulate intestinal flora and immune responses effectively. l-arginine is converted into nitric oxide to regulate the gut microbiome, while MXene serves as a nanoimmunomodulator to stabilize immune homeostasis. Our findings demonstrate that the anti-inflammatory properties of the microspheres are key to promoting epithelial repair and remodeling of the ISC niche. This study highlights the role of antioxidant microspheres as anti-inflammatory agents that indirectly support ISC function and gut regeneration.

PPM1G dephosphorylates eIF4E in control of mRNA translation and cell proliferation

The mRNA 5'cap-binding eukaryotic translation initiation factor 4E (eIF4E) plays a critical role in the control of mRNA translation in health and disease. One mechanism of regulation of eIF4E activity is via phosphorylation of eIF4E by MNK kinases, which promotes the translation of a subset of mRNAs encoding pro-tumorigenic proteins. Work on eIF4E phosphatases has been paltry. Here, we show that PPM1G is the phosphatase that dephosphorylates eIF4E. We describe the eIF4E-binding motif in PPM1G that is similar to 4E-binding proteins (4E-BPs). We demonstrate that PPM1G inhibits cell proliferation by targeting phospho-eIF4E-dependent mRNA translation.

PP2Ac knockdown attenuates lipotoxicity‑induced pancreatic β‑cell dysfunction and apoptosis

Protein phosphatase 2A (PP2A) is one of the most common serine/threonine phosphatases in mammalian cells, and it primarily functions to regulate cell signaling, glycolipid metabolism and apoptosis. The catalytic subunit of PP2A (PP2Ac) plays an important role in the functions of the protein. However, there are few reports on the regulatory role of PP2Ac in pancreatic β-cells under lipotoxic conditions. In the present study, mouse insulinoma 6 (MIN6) pancreatic cells were transfected with short hairpin RNAs to generate PP2Ac knockdown cells and incubated with palmitate (PA) to establish a lipotoxicity model. Serine/threonine phosphatase assay system, Cell Counting Kit-8, flow cytometry, enzyme-linked immunosorbent assay and western blotting were used to measure PP2A activity, cell viability, apoptosis, oxidative stress and insulin secretion in the cells. In addition, a mouse model of lipotoxicity was established with a high-fat diet (HFD) and the knockdown of PP2Ac using adeno-associated viruses to interfere with PP2Ac expression in the pancreatic tissues. The activity of PP2A in the mouse pancreatic tissue and the serum insulin level were measured. Furthermore, the proliferation of mouse pancreatic β-cells was assessed using pancreatic tissue immunofluorescence. PP2Ac knockdown inhibited lipotoxicity-induced PP2A hyperactivation, increased the resistance of pancreatic β-cells to lipotoxicity and attenuated PA-induced apoptosis in MIN6 cells. It also protected the endoplasmic reticulum and mitochondria, and ameliorated insulin secretion. The results of mRNA sequencing and western blotting analysis suggested that the protective effects of PP2Ac knockdown in MIN6 cells may be mediated via the MAPK pathway. Moreover, the results of the animal experiments suggested that specific knockdown of pancreatic PP2Ac effectively attenuated HFD-induced insulin resistance and reduced the compensatory proliferation of pancreatic β-cells in mice. In summary, the present study revealed the effects of interfering with PP2Ac gene expression on pancreatic β-cells in vivo and in vitro and the underlying mechanisms, which may provide insights for the treatment of type 2 diabetes mellitus in the clinic.

Aloperine inhibits the progression of non-small-cell lung cancer through the PI3K/Akt signaling pathway

Background

Lung cancer has become the leading cause of cancer-related death worldwide and non‐small‐cell lung cancer (NSCLC) accounts for approximately 85% of cases. Aloperine (ALO), an alkaloid active natural component from S. alopecuroide, has been found to exhibit anti-inflammatory, anti-tumor and anti-viral activity. However, Whether ALO exerts anti-tumor function on NSCLC remains poorly understood, and the underlying mechanisms remain unknown.

Methods

The CCK-8, colony formation, cell apoptosis with flow cytometry, wound healing and transwell cell invasion assays, were used to analyze the tumor progression of H1299 and A549 cells treated with ALO in vitro, and the xenograft model was constructed to assess the effect of ALO in vivo. The expression of protein was detected by Western blotting.

Results

ALO suppressed the cell proliferation, self-renewal, migration and invasion, induced apoptosis in A549 and H1299 cell. Furthermore, ALO significantly enhanced the level of cytochrome c in cytosol, and resulted in the dramatical increased levels of the cleaved caspase-3, caspased-9 and PARP. ALO also inhibited the expression of MMP-2 and MMP-9. Additionally, ALO also reduced p-AKT and p-mTOR to attenuate the PI3K/AKT signaling pathway.

Conclusion

This study unveils a rationale for ALO through PI3K/Akt signaling pathway affecting the cell progression such as cell growth, apoptosis and invasion, and ALO acts as a potential chemotherapeutic agent for NSCLC.

Comparative proteomic analysis provides insight into the key proteins as potential targets underlying the effect of malachite green against Ichthyophthirius multifiliis

Target identification is important for drug discovery. Unfortunately, no drug targets have been found in Ichthyophthirius multifiliis until now and further limited development of the novel drug for Ichthyophthiriasis. In this study, an iTRAQ-based quantitative proteomic analysis was used to find the target of malachite green (MG), exhibiting greater efficacy than the existing drugs, against I. multifiliis trophonts in situ. We also verified the proteomic results by RT-qPCR, TEM and cell apoptosis assay. Our results showed that major variations in protein abundance were found among many of the ribosome proteins, indicating ribosome might be a candidate target. Furthermore, GO and KEGG pathway analyses of differentially expressed proteins (DEPs) revealed that ribosome and PI3K-Akt signalling pathway were remarkably enriched. Taken together, the above DEPs were also verified by RT-qPCR and morphological observations. This study provides insights into the key proteins enriched in PI3K-Akt signal pathway and ribosome pathway as potential targets of MG killing I. multifiliis, which could be served as targets for other less toxic drugs and be tested as potential treatments for I. multifiliis.

PP2A and tumor radiotherapy

Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that serves as a key regulator of cellular physiology in the context of apoptosis, mitosis, and DNA damage responses. Canonically, PP2A functions as a tumor suppressor gene. However, recent evidence suggests that inhibiting PP2A activity in tumor cells may represent a viable approach to enhancing tumor sensitivity to chemoradiotherapy as such inhibition can cause cells to enter a disordered mitotic state that renders them more susceptible to cell death. Indeed, there is evidence that inhibiting PP2A can slow tumor growth following radiotherapy in a range of cancer types including ovarian cancer, liver cancer, malignant glioma, pancreatic cancer, and nasopharyngeal carcinoma. In the present review, we discuss current understanding of the role of PP2A in tumor radiotherapy and the potential mechanisms whereby it may influence this process.

Inhibition of PP2A enhances the osteogenic differentiation of human aortic valvular interstitial cells via ERK and p38 MAPK pathways

AIMS

To investigate the role of PP2A in calcified aortic valve disease (CAVD).

MATERIALS AND METHODS

The expressions of PP2A subunits were detected by real-time polymerase chain reaction (RT-PCR) and western blot in aortic valves from patients with CAVD and normal controls, the activities of PP2A were analyzed by commercial assay kit at the same time. Aortic valve calcification of mice was evaluated through histological and echocardiographic analysis. ApoE^-/- mice and ApoE^-/- mice injected intraperitoneally with PP2A inhibitor LB100 were fed a high-cholesterol diet for 24 weeks. Immunofluorescent staining was used to locate the cell-type in which PP2A activity was decreased, the PP2A activity of valvular interstitial cells (VICs) treated with osteogenic induction medium was assessed by western blot and commercial assay kit. After changing the activity of VICs through pharmacologic and genetic intervention, the osteoblast differentiation and mineralization were assessed by western blot and Alizarin Red staining. Finally, the mechanism was clarified by using several specific inhibitors.

KEY FINDINGS

PP2A activity was decreased both in calcified aortic valves and human VICs under osteogenic induction. The PP2A inhibitor LB100 aggravated the aortic valve calcification of mice. Furthermore, PPP2CA overexpression inhibited osteogenic differentiation of VICs, whereas PPP2CA knockdown promoted the process. Further study revealed that the ERK/p38 MAPKs signaling pathways mediated the osteogenic differentiation of VICs induced by PP2A inactivation.

SIGNIFICANCE

This study demonstrated that PP2A plays an important role in CAVD pathophysiology, PP2A activation may provide a novel strategy for the pharmacological treatment of CAVD.