Insights from molecular modeling into the selective inhibition of cathepsin S by its inhibitor

Small Vessel Disease: Ancient Description, Novel Biomarkers

Small vessel disease (SVD) is one of the most frequent pathological conditions which lead to dementia. Biochemical and neuroimaging might help correctly identify the clinical diagnosis of this relevant brain disease. The microvascular alterations which underlie SVD have common origins, similar cognitive outcomes, and common vascular risk factors. Nevertheless, the arteriolosclerosis process, which underlines SVD development, is based on different mechanisms, not all completely understood, which start from a chronic hypoperfusion state and pass through a chronic brain inflammatory condition, inducing a significant endothelium activation and a consequent tissue remodeling action. In a recent review, we focused on the pathophysiology of SVD, which is complex, involving genetic conditions and different co-morbidities (i.e., diabetes, chronic hypoxia condition, and obesity). Currently, many points still remain unclear and discordant. In this paper, we wanted to focus on new biomarkers, which can be the expression of the endothelial dysfunction, or of the oxidative damage, which could be employed as markers of disease progression or for future targets of therapies. Therefore, we described the altered response to the endothelium-derived nitric oxide-vasodilators (ENOV), prostacyclin, C-reactive proteins, and endothelium-derived hyperpolarizing factors (EDHF). At the same time, due to the concomitant endothelial activation and chronic neuroinflammatory status, we described hypoxia-endothelial-related markers, such as HIF 1 alpha, VEGFR2, and neuroglobin, and MMPs. We also described blood–brain barrier disruption biomarkers and imaging techniques, which can also describe perivascular spaces enlargement and dysfunction. More studies should be necessary, in order to implement these results and give them a clinical benefit.

Therapeutic potential of targeting cathepsin S in pulmonary fibrosis

Cathepsin S (CTSS), a lysosomal protease, belongs to a family of cysteine cathepsin proteases that promote degradation of damaged proteins in the endolysosomal pathway. Aberrant CTSS expression and regulation are associated with the pathogenesis of several diseases, including lung diseases. CTSS overexpression causes a variety of pathological processes, including pulmonary fibrosis, with increased CTSS secretion and accelerated extracellular matrix remodeling. Compared to many other cysteine cathepsin family members, CTSS has unique features that it presents limited tissue expression and retains its enzymatic activity at a neutral pH, suggesting its decisive involvement in disease microenvironments. In this review, we investigated the role of CTSS in lung disease, exploring recent studies that have indicated that CTSS mediates fibrosis in unique ways, along with its structure, substrates, and distinct regulation. We also outlined examples of CTSS inhibitors in clinical and preclinical development and proposed CTSS as a potential therapeutic target for pulmonary fibrosis.

Inflammation and tumor progression: signaling pathways and targeted intervention

Cancer development and its response to therapy are regulated by inflammation, which either promotes or suppresses tumor progression, potentially displaying opposing effects on therapeutic outcomes. Chronic inflammation facilitates tumor progression and treatment resistance, whereas induction of acute inflammatory reactions often stimulates the maturation of dendritic cells (DCs) and antigen presentation, leading to anti-tumor immune responses. In addition, multiple signaling pathways, such as nuclear factor kappa B (NF-kB), Janus kinase/signal transducers and activators of transcription (JAK-STAT), toll-like receptor (TLR) pathways, cGAS/STING, and mitogen-activated protein kinase (MAPK); inflammatory factors, including cytokines (e.g., interleukin (IL), interferon (IFN), and tumor necrosis factor (TNF)-α), chemokines (e.g., C-C motif chemokine ligands (CCLs) and C-X-C motif chemokine ligands (CXCLs)), growth factors (e.g., vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β), and inflammasome; as well as inflammatory metabolites including prostaglandins, leukotrienes, thromboxane, and specialized proresolving mediators (SPM), have been identified as pivotal regulators of the initiation and resolution of inflammation. Nowadays, local irradiation, recombinant cytokines, neutralizing antibodies, small-molecule inhibitors, DC vaccines, oncolytic viruses, TLR agonists, and SPM have been developed to specifically modulate inflammation in cancer therapy, with some of these factors already undergoing clinical trials. Herein, we discuss the initiation and resolution of inflammation, the crosstalk between tumor development and inflammatory processes. We also highlight potential targets for harnessing inflammation in the treatment of cancer.

Homocysteine in Neurology: A Possible Contributing Factor to Small Vessel Disease

Homocysteine (Hcy) is a sulfur-containing amino acid generated during methionine metabolism, accumulation of which may be caused by genetic defects or the deficit of vitamin B12 and folate. A serum level greater than 15 micro-mols/L is defined as hyperhomocysteinemia (HHcy). Hcy has many roles, the most important being the active participation in the transmethylation reactions, fundamental for the brain. Many studies focused on the role of homocysteine accumulation in vascular or degenerative neurological diseases, but the results are still undefined. More is known in cardiovascular disease. HHcy is a determinant for the development and progression of inflammation, atherosclerotic plaque formation, endothelium, arteriolar damage, smooth muscle cell proliferation, and altered-oxidative stress response. Conversely, few studies focused on the relationship between HHcy and small vessel disease (SVD), despite the evidence that mice with HHcy showed a significant end-feet disruption of astrocytes with a diffuse SVD. A severe reduction of vascular aquaporin-4-water channels, lower levels of high-functioning potassium channels, and higher metalloproteinases are also observed. HHcy modulates the N-homocysteinylation process, promoting a pro-coagulative state and damage of the cellular protein integrity. This altered process could be directly involved in the altered endothelium activation, typical of SVD and protein quality, inhibiting the ubiquitin-proteasome system control. HHcy also promotes a constant enhancement of microglia activation, inducing the sustained pro-inflammatory status observed in SVD. This review article addresses the possible role of HHcy in small-vessel disease and understands its pathogenic impact.

Molecular modeling assisted identification and biological evaluation of potent cathepsin S inhibitors

Cathepsin S (CatS) is one of the cysteinyl cathepsins widely studied for its clinical significance and found to be a promising therapeutic target for several diseases; to name a few is arthritis, allergic inflammation, cancer, diabetes, obesity, and cystic fibrosis. Elevated CatS level is a contributing factor for related disorders, and therefore among different strategies to regulate the activity of CatS, one is to design a quality inhibitor. Earlier, we have demonstrated a highly selective CatS inhibitor, RO5444101 interacts primarily with the S2 pocket of the protein which is structurally unique in contrast to other variants of cathepsin. However, the molecular properties of RO5444101 can question its efficacy at the clinical level. In the present study, we have implemented a series of molecular modeling methods to screen the Maybridge library considering the pharmacophoric features of RO5444101 and other relevant inhibitors of CatS. Based on the priority list, eight hits were subjected to biological evaluation. Subsequently, KM07987 was found to be most potent, with the IC₅₀ of <5 μM. Molecular dynamics simulations also relate to our experimental findings and propose the importance of CatS's S2 pocket, which primarily interacts with the inhibitors. Based on the S2 pocket interactions, structural modifications of the promising hits can further be translated into novel scaffolds for improved inhibition of CatS.

Urinary proteome analysis of acute hypercoagulable state in rat model induced by ε-aminocaproic acid

The hypercoagulable state occurs in a group of prothrombotic disorders associated with an increased risk for thromboembolic events, but it is difficult to diagnose due to the lack of available biomarkers. This study aimed to investigate systematic changes of urinary proteome in acute hypercoagulable state induced by certain antifibrinolytics. To reduce the effects of both genetic and environmental factors on the urinary proteome, we used a rat model of acute hypercoagulable state induced by an antifibrinolytic agent ε-aminocaproic acid, resembling human hypercoagulable state. Urine samples were collected during acute hypercoagulable state for analysis by liquid chromatography-tandem mass spectrometry (LCMS/MS). Of 65 significantly changed proteins in acute hypercoagulable state, 38 proteins had human orthologs, and 18 proteins were identified as stable in normal human urine. None of the identified proteins have been found to be clotting factors, but 4 proteins are known to be involved in the regulation of blood coagulation factors. Two proteins were verified as the markers associated with acute hypercoagulable state by Western blot analysis. In addition, four common differential urinary proteins have been found in acute hypercoagulable state induced by another antifibrinolytics tranexamic acid. These four proteins are potential biomarkers for early diagnosis of hypercoagulable state to prevent the development of thrombotic diseases.

Cathepsin S As an Inhibitor of Cardiovascular Inflammation and Calcification in Chronic Kidney Disease

Cardiovascular disease (CVD) is responsible for the majority of deaths in the developed world. Particularly, in patients with chronic kidney disease (CKD), the imbalance of calcium and phosphate may lead to the acceleration of both vascular and valve inflammation and calcification. One in two patients with CKD are reported as dying from cardiovascular causes due to the resulting acceleration in the development of atherosclerosis plaques. In addition, CKD patients on hemodialysis are prone to aortic valve calcification and often need valve replacement before kidney transplantation. The lysosomal proteases, cathepsins, are composed of 11 cysteine members (cathepsin B, C, F, H, K, L, O, S, V, W, and Z), as well as serine proteases cathepsin A and G, which cleave peptide bonds with serine as the amino acid, and aspartyl proteases D and E, which use an activated water molecule bound to aspartate to break peptide substrate. Cysteine proteases, also known as thiol proteases, degrade protein via the deprotonation of a thiol and have been found to play a significant role in autoimmune disease, atherosclerosis, aortic valve calcification, cardiac repair, and cardiomyopathy, operating within extracellular spaces. This review sought to evaluate recent findings in this field, highlighting how among cathepsins, the inhibition of cathepsin S in particular, could play a significant role in diminishing the effects of CVD, especially for patients with CKD.

Synthesis and biological evaluation of novel synthetic chalcone derivatives as anti-tumor agents targeting Cat L and Cat K

A series of chalcone derivatives bearing benzamide or benzenesulfonamide moieties were synthesized and evaluated for their anti-tumor effect on HCT116, MCF7 and 143B cell lines in vitro. SAR analysis showed that compounds bearing a benzenesulfonamide group had greater potency than those bearing a benzamide group. It was also shown that compounds with a mono-methyl or mono-halogen group at the 3-position on the terminal phenyl ring were more effective than those with trifluoromethyl or methoxy groups. Compound 8e exhibited the most potent anti-tumor activities against HCT116, MCF7 and 143B cell lines, with IC₅₀ values of 0.597, 0.886 and 0.791μM, respectively. Molecular docking studies and enzymatic assays demonstrated that the anti-tumor activity of compound 8e might be regulated by Cat L and Cat K.