Luteolin ameliorates necroptosis in Glucocorticoid-induced osteonecrosis of the femoral head via RIPK1/RIPK3/MLKL pathway based on network pharmacology analysis

MLKL as an emerging machinery for modulating organelle dynamics: regulatory mechanisms, pathophysiological significance, and targeted therapeutics

Mixed lineage kinase domain-like protein (MLKL) is a pseudokinase featured by a protein kinase-like domain without catalytic activity. MLKL was originally discovered to be phosphorylated by receptor-interacting protein kinase 1/3, typically increase plasma membrane permeabilization, and disrupt the membrane integrity, ultimately executing necroptosis. Recent evidence uncovers the association of MLKL with diverse cellular organelles, including the mitochondrion, lysosome, endosome, endoplasmic reticulum, and nucleus. Thus, this review mainly focuses on the regulatory functions, mechanisms, and targets of MLKL in organelles rather than necroptosis and summarize the medical significance in multiple diseases. On this basis, we conclude and analyze the current progress and prospect for the development of MLKL-related drugs, from natural products, small-molecule chemical compounds, to proteolysis-targeting chimera. This review is aimed to propel the development of MLKL as a valid drug target and the discovery of novel MLKL-related drugs, and promote their further applications.

Astaxanthin Prevents Glucocorticoid-Induced Femoral Head Osteonecrosis by Targeting Ferroptosis through the JAK2/STAT3 Signaling Pathway

Glucocorticoid (GC) is extensively used in clinical practice, and the osteonecrosis of the femoral head caused by them is a common issue in orthopedic surgery, yet the underlying mechanisms remain unclear. Astaxanthin (AST), a potent natural antioxidant, has an unexplored impact on GC-induced osteonecrosis of the femoral head (GIONFH). This study explores the effects and mechanisms of AST in counteracting dexamethasone (Dex)-induced ferroptosis and GIONFH. We developed a rat model of GIONFH using intraperitoneal Dex injections and conducted in vitro analysis by culturing osteoblasts (OBs) with Dex treatment. We assessed the impact of AST on Dex-treated OBs using C11-BODIPY and FerroOrange staining, mitochondrial functionality tests, and protein expression analyses through Western blot and immunofluorescence. The influence of AST on bone microarchitecture of femoral head in rat was assessed using micro-CT, hematoxylin and eosin staining, immunofluorescence, and immunohistochemistry at imaging and histological levels. Our findings suggest that AST exerts an inhibitory effect on Dex-induced ferroptosis and GIONFH. In vitro, AST treatment increased glutathione and decreased malondialdehyde, lipid peroxidation, and mitochondrial-reactive oxygen species. Additionally, AST treatment also enhances the phosphorylation of STAT3, upregulates glutathione peroxidase 4 and osteogenic-related proteins, and stimulates bone formation. To delve deeper into the mechanism, the findings revealed that AST triggered activation of JAK2/STAT3 signaling. Moreover, the use of siRNA-STAT3 blocked the beneficial effect of AST in OBs cultivated with Dex. In brief, AST combats GIONFH by activating the JAK2/STAT3 pathway to inhibit ferroptosis.

VPO1 Promotes Programmed Necrosis of Cardiomyocytes in Rats with Chronic Heart Failure by Upregulating CYLD

BACKGROUND

Chronic heart failure (CHF) is a serious cardiovascular condition. Vascular peroxidase 1 (VPO1) is associated with various cardiovascular diseases, yet its role in CHF remains unclear. This research aims to explore the involvement of VPO1 in CHF.

METHODS

CHF was induced in rats using adriamycin, and the expression levels of VPO1 and cylindromatosis (CYLD) were assessed. In parallel, the effects of VPO1 on programmed necrosis in H9c2 cells were evaluated through cell viability assays, lactate dehydrogenase (LDH) level measurements, and analysis of receptor-interacting protein kinase 1/receptor-interacting protein kinase 3/mixed lineage kinase domain-like protein (RIPK1/RIPK3/MLKL) pathway-related proteins. The impact of CYLD on RIPK1 protein stability and ubiquitination was also investigated, along with the interaction between VPO1 and CYLD. Additionally, cardiac structure and function were assessed using echocardiography, Hematoxylin-eosin (HE) staining, Masson staining, and measurements of myocardial injury-related factors, including N-terminal prohormone of brain natriuretic peptide (NT-proBNP), Aspartate aminotransferase (AST), LDH, and creatine kinase-myocardial band (CK-MB).

RESULTS

VPO1 expression was upregulated in CHF rats and in H9c2 cells treated with adriamycin. In cellular experiments, VPO1 knockdown improved cell viability, inhibited necrosis and the expression of proteins associated with the RIPK1/RIPK3/MLKL pathway. Mechanistically, VPO1 promoted cardiomyocyte programmed necrosis by interacting with the deubiquitinating enzyme CYLD, which enhanced RIPK1 ubiquitination and degradation, leading to activation of the RIPK1/RIPK3/MLKL signaling pathway. At animal level, overexpression of CYLD counteracted the cardiac failure, cardiac hypertrophy, myocardial injury, myocardial fibrosis, and tissue necrosis caused by VPO1 knockdown.

CONCLUSIONS

VPO1 exacerbates cardiomyocyte programmed necrosis in CHF rats by upregulating CYLD, which activates the RIPK1/RIPK3/MLKL signaling pathway. Thus, VPO1 may represent a potential therapeutic target for CHF.

Mechanism of action of Salvia miltiorrhiza on avascular necrosis of the femoral head determined by integrated network pharmacology and molecular dynamics simulation

Avascular necrosis of the femoral head (ANFH) is a progressive, multifactorial, and challenging clinical condition that often leads to hip dysfunction and deterioration. The pathogenesis of ANFH is complex, and there is no foolproof treatment strategy. Although some pharmacologic and surgical treatments have been shown to improve ANFH, the associated side effects and poor prognosis are of concern. Therefore, there is an urgent need to explore therapeutic interventions with superior efficacy and safety to improve the quality of life of patients with ANFH. Salvia miltiorrhiza (SM), a traditional Chinese medicine with a long history, is widely used for the treatment of cardiovascular and musculoskeletal diseases due to its multiple pharmacological activities. However, the molecular mechanism of SM for the treatment of ANFH is still unclear. Therefore, this study aimed to explore the potential targets and mechanisms of SM for the treatment of ANFH using network pharmacology and molecular modeling techniques. By searching multiple databases, we screened 52 compounds and 42 common targets involved in ANFH therapy and identified dan-shexinkum d, cryptotanshinone, tanshinone iia, and dihydrotanshinlactone as key compounds. Based on the protein-protein interaction (PPI) network, TP53, AKT1, EGFR, STAT3, BCL2, IL6, and TNF were identified as core targets. Subsequent enrichment analysis revealed that these targets were mainly enriched in the AGE-RAGE, IL-17, and TNF pathways, which were mainly associated with inflammatory responses, apoptosis, and oxidative stress. In addition, molecular docking and 100 nanoseconds molecular dynamics (MD) simulations showed that the bioactive compounds of SM had excellent affinity and binding strength to the core targets. Among them, dan-shexinkum d possessed the lowest binding free energy (-215.874 kcal/mol and - 140.277 kcal/mol, respectively) for AKT1 and EGFR. These results demonstrated the multi-component, multi-target, and multi-pathway intervention mechanism of SM in the treatment of ANFH, which provided theoretical basis and clues for further experimental validation and development of anti-ANFH drugs.

Virtual screening of flavonoids as potential RIPK1 inhibitors for neurodegeneration therapy

Background

Global prevalence of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease is increasing gradually, whereas approvals of successful therapeutics for central nervous system disorders are inadequate. Accumulating evidence suggests pivotal roles of the receptor-interacting serine/threonine-protein kinase 1 (RIPK1) in modulating neuroinflammation and necroptosis. Discoveries of potent small molecule inhibitors for RIPK1 with favorable pharmacokinetic properties could thus address the unmet medical needs in treating neurodegeneration.

Methods

In a structure-based virtual screening, we performed site-specific molecular docking of 4,858 flavonoids against the kinase domain of RIPK1 using AutoDock Vina. We predicted physicochemical descriptors of the top ligands using the SwissADME webserver. Binding interactions of the best ligands and the reference ligand L8D were validated using replicated 500-ns Gromacs molecular dynamics simulations and free energy calculations.

Results

From Vina docking, we shortlisted the top 20 flavonoids with the highest binding affinities, ranging from -11.7 to -10.6 kcal/mol. Pharmacokinetic profiling narrowed down the list to three orally bioavailable and blood-brain-barrier penetrant flavonoids: Nitiducarpin, Pinocembrin 7-O-benzoate, and Paratocarpin J. Next, trajectories of molecular dynamics simulations of the top protein-ligand complexes were analyzed for binding interactions. The root-mean-square deviation (RMSD) was 1.191 Å (±0.498 Å), 1.725 Å (±0.828 Å), 1.923 Å (±0.942 Å), 0.972 Å (±0.155 Å) for Nitiducarpin, Pinocembrin 7-O-benzoate, Paratocarpin J, and L8D, respectively. The radius of gyration (Rg) was 2.034 nm (±0.015 nm), 2.0.39 nm (± 0.025 nm), 2.053 nm (±0.021 nm), 2.037 nm (±0.016 nm) for Nitiducarpin, Pinocembrin 7-O-benzoate, Paratocarpin J, and L8D, respectively. The solvent accessible surface area (SASA) was 159.477 nm2 (±3.021 nm2), 159.661 nm2 (± 3.707 nm2), 160.755 nm2 (±4.252 nm2), 156.630 nm2 (±3.521 nm2), for Nitiducarpin, Pinocembrin 7-O-benzoate, Paratocarpin J, and L8D complexes, respectively. Therefore, lower RMSD, Rg, and SASA values demonstrated that Nitiducarpin formed the most stable complex with the target protein among the best three ligands. Finally, 2D protein-ligand interaction analysis revealed persistent hydrophobic interactions of Nitiducarpin with the critical residues of RIPK1, including the catalytic triads and the activation loop residues, implicated in the kinase activity and ligand binding.

Conclusion

Our target-based virtual screening identified three flavonoids as strong RIPK1 inhibitors, with Nitiducarpin exhibiting the most potent inhibitory potential. Future in vitro and in vivo studies with these ligands could offer new hope for developing effective therapeutics and improving the quality of life for individuals affected by neurodegeneration.

The Role of Herbal Medicine in Modulating Bone Homeostasis

Osteoporosis and other bone diseases are a major public health concern worldwide. Current pharmaceutical treatments for bone disorders have limitations, driving interest in complementary herbal medicines that can help maintain bone health. This review summarizes the scientific evidence for medicinal herbs that modulate bone cell activity and improve bone mass, quality and strength. Herbs with osteogenic, anti-osteoporotic, and anti-osteoclastic effects are discussed, including compounds and mechanisms of action. Additionally, this review examines the challenges and future directions for translational research on herbal medicines for osteoporosis and bone health. While preliminary research indicates beneficial bone bioactivities for various herbs, rigorous clinical trials are still needed to verify therapeutic efficacy and safety. Further studies should also elucidate synergistic combinations, bioavailability of active phytochemicals, and precision approaches to match optimal herbs with specific etiologies of bone disease. Advancing evidence- based herbal medicines may provide novel alternatives for promoting bone homeostasis and treating skeletal disorders.

Repressive Control of Keratinocyte Cytoplasmic Inflammatory Signaling

The overactivity of keratinocyte cytoplasmic signaling contributes to several cutaneous inflammatory and immune pathologies. An important emerging complement to proteins responsible for this overactivity is signal repression brought about by several proteins and protein complexes with the native role of limiting inflammation. The signaling repression by these proteins distinguishes them from transmembrane receptors, kinases, and inflammasomes, which drive inflammation. For these proteins, defects or deficiencies, whether naturally arising or in experimentally engineered skin inflammation models, have clearly linked them to maintaining keratinocytes in a non-activated state or returning cells to a post-inflamed state after a signaling event. Thus, together, these proteins help to resolve acute inflammatory responses or limit the development of chronic cutaneous inflammatory disease. We present here an integrated set of demonstrated or potentially inflammation-repressive proteins or protein complexes (linear ubiquitin chain assembly complex [LUBAC], cylindromatosis lysine 63 deubiquitinase [CYLD], tumor necrosis factor alpha-induced protein 3-interacting protein 1 [TNIP1], A20, and OTULIN) for a comprehensive view of cytoplasmic signaling highlighting protein players repressing inflammation as the needed counterpoints to signal activators and amplifiers. Ebb and flow of players on both sides of this inflammation equation would be of physiological advantage to allow acute response to damage or pathogens and yet guard against chronic inflammatory disease. Further investigation of the players responsible for repressing cytoplasmic signaling would be foundational to developing new chemical-entity pharmacologics to stabilize or enhance their function when clinical intervention is needed to restore balance.