Preclinical and Clinical Studies of p38α MAP kinase inhibition to Treat Basal Forebrain Cholinergic Dysfunction and Degeneration

The endosome-associated protein Rab5 is a central player in the molecular mechanisms leading to degeneration of basal forebrain cholinergic neurons (BFCN), a long-standing target for drug development. As p38α kinase is a Rab-5 activator, we hypothesized that inhibition of this kinase held potential as an approach to treat diseases associated with BFCN loss. Herein we report that treatment with an oral small molecule p38α kinase inhibitor reversed pathological disease progression in the basal forebrain in a mouse model that develops BFCN degeneration. Further, the preclinical results were successfully translated to the clinic, with improvement of clinical outcomes associated with cholinergic function in a clinical study in dementia with Lewy bodies (DLB), a disease in which BFCN dysfunction and degeneration is the primary driver of disease expression. The findings both advances a novel approach to treating DLB and validates the translational platform that provided the mechanistic rationale for advancing that approach.

Synthesis and Biological Evaluation of 2,3,4-Triaryl-1,2,4-oxadiazol-5-ones as p38 MAPK Inhibitors

A series of azastilbene derivatives, characterized by the presence of the 1,2,4-oxadiazole-5-one system as a linker of the two aromatic rings of stilbenes, have been prepared as novel potential inhibitors of p38 MAPK. Biological assays indicated that some of the synthesized compounds are endowed with good inhibitory activity towards the kinase. Molecular modeling data support the biological results showing that the designed compounds possess a reasonable binding mode in the ATP binding pocket of p38α kinase with a good binding affinity.

P38α MAPK Signaling—A Robust Therapeutic Target for Rab5-Mediated Neurodegenerative Disease

Multifactorial pathologies, involving one or more aggregated protein(s) and neuroinflammation are common in major neurodegenerative diseases, such as Alzheimer’s disease and dementia with Lewy bodies. This complexity of multiple pathogenic drivers is one potential explanation for the lack of success or, at best, the partial therapeutic effects, respectively, with approaches that have targeted one specific driver, e.g., amyloid-beta, in Alzheimer’s disease. Since the endosome-associated protein Rab5 appears to be a convergence point for many, if not all the most prominent pathogenic drivers, it has emerged as a major therapeutic target for neurodegenerative disease. Further, since the alpha isoform of p38 mitogen-activated protein kinase (p38α) is a major regulator of Rab5 activity and its effectors, a biology that is distinct from the classical nuclear targets of p38 signaling, brain-penetrant selective p38α kinase inhibitors provide the opportunity for significant therapeutic advances in neurogenerative disease through normalizing dysregulated Rab5 activity. In this review, we provide a brief summary of the role of Rab5 in the cell and its association with neurodegenerative disease pathogenesis. We then discuss the connection between Rab5 and p38α and summarize the evidence that through modulating Rab5 activity there are therapeutic opportunities in neurodegenerative diseases for p38α kinase inhibitors.

Prostaglandins Isolated from the Octocoral Plexaura homomalla: In Silico and In Vitro Studies Against Different Enzymes of Cancer

Prostaglandin A2-AcMe (1) and Prostaglandin A2 (2) were isolated from the octocoral Plexaura homomalla and three semisynthetic derivatives (3–5) were then obtained using a reduction protocol. All compounds were identified through one- and two-dimensional (1D and 2D) nuclear magnetic resonance (NMR) experiments. Additionally, evaluation of in vitro cytotoxic activity against the breast (MDA-MB-213) and lung (A549) cancer cell lines, in combination with enzymatic activity and molecular docking studies with the enzymes p38α-kinase, Src-kinase, and topoisomerase IIα, were carried out for compounds 1–5 in order to explore their potential as inhibitors of cancer-related molecular targets. Results showed that prostaglandin A2 (2) was the most potent compound with an IC50 of 16.46 and 25.20 μg/mL against MDA-MB-213 and A549 cell lines, respectively. In addition, this compound also inhibited p38α-kinase in 49% and Src-kinase in 59% at 2.5 μM, whereas topoisomerase IIα was inhibited in 64% at 10 μM. Enzymatic activity was found to be consistent with molecular docking simulations, since compound 2 also showed the lowest docking scores against the topoisomerase IIα and Src-kinase (−8.7 and −8.9 kcal/mol, respectively). Thus, molecular docking led to establish some insights into the predicted binding modes. Results suggest that prostaglandin 2 can be considered as a potential lead for development inhibitors against some enzymes present in cancer processes.

TAB1-Induced Autoactivation of p38α Mitogen-Activated Protein Kinase Is Crucially Dependent on Threonine 185

ABSTRACT p38α mitogen-activated protein kinase is essential to cellular homeostasis. Two principal mechanisms to activate p38α exist. The first relies on dedicated dual-specificity kinases such as mitogen-activated protein kinase kinase (MAP2K) 3 (MKK3) or 6 (MKK6), which activate p38α by phosphorylating Thr180 and Tyr182 within the activation segment. The second is by autophosphorylation of Thr180 and Tyr182 in cis , mediated by p38α binding the scaffold protein TAB1. The second mechanism occurs during myocardial ischemia, where it aggravates myocardial infarction. Based on the crystal structure of the p38α-TAB1 complex we replaced threonine 185 of p38α with glycine (T185G) to prevent an intramolecular hydrogen bond with Asp150 from being formed. This mutation did not interfere with TAB1 binding to p38α. However, it disrupted the consequent long-range effect of this binding event on the distal activation segment, releasing the constraint on Thr180 that oriented its hydroxyl for phosphotransfer. Based on assays performed in vitro and in vivo , the autoactivation of p38α(T185G) was disabled, while its ability to be activated by upstream MAP2Ks and to phosphorylate downstream substrates remained intact. Furthermore, myocardial cells expressing p38α(T185G) were resistant to injury. These findings reveal a mechanism to selectively disable p38α autoactivation and its consequences, which may ultimately circumvent the toxicity associated with strategies that inhibit p38α kinase activity under all circumstances, such as with ATP-competitive inhibitors.

Changes in the free-energy landscape of p38α MAP kinase through its canonical activation and binding events as studied by enhanced molecular dynamics simulations

p38α is a Ser/Thr protein kinase involved in a variety of cellular processes and pathological conditions, which makes it a promising pharmacological target. Although the activity of the enzyme is highly regulated, its molecular mechanism of activation remains largely unexplained, even after decades of research. By using state-of-the-art molecular dynamics simulations, we decipher the key elements of the complex molecular mechanism refined by evolution to allow for a fine tuning of p38α kinase activity. Our study describes for the first time the molecular effects of different regulators of the enzymatic activity, and provides an integrative picture of the activation mechanism that explains the seemingly contradictory X-ray and NMR data.

Biophysical investigation and conformational analysis of p38α kinase inhibitor doramapimod and its analogues

Doramapimod (BIRB 796) is a potent inhibitor of p38α nitrogen-activated protein kinase. By using biophysical methods, a clear correlation between kinase binding and the torsion angle θ of doramapimod analogues was found, highlighting the importance of inhibitor conformation for protein binding.