Peroxynitrite Exposure of CXCL12 Impairs Monocyte, Lymphocyte and Endothelial Cell Chemotaxis, Lymphocyte Extravasation in vivo and Anti-HIV-1 Activity

Proteolytic inactivation of CXCL12 in the lungs and circulation of COVID-19 patients

The human chemokine stromal cell-derived factor-1 (SDF-1) or CXCL12 is involved in several homeostatic processes and pathologies through interaction with its cognate G protein-coupled receptor CXCR4. Recent research has shown that CXCL12 is present in the lungs and circulation of patients with coronavirus disease 2019 (COVID-19). However, the question whether the detected CXCL12 is bioactive was not addressed. Indeed, the activity of CXCL12 is regulated by NH2- and COOH-terminal post-translational proteolysis, which significantly impairs its biological activity. The aim of the present study was to characterize proteolytic processing of CXCL12 in broncho-alveolar lavage (BAL) fluid and blood plasma samples from critically ill COVID-19 patients. Therefore, we optimized immunosorbent tandem mass spectrometry proteoform analysis (ISTAMPA) for detection of CXCL12 proteoforms. In patient samples, this approach uncovered that CXCL12 is rapidly processed by site-specific NH2- and COOH-terminal proteolysis and ultimately degraded. This proteolytic inactivation occurred more rapidly in COVID-19 plasma than in COVID-19 BAL fluids, whereas BAL fluid samples from stable lung transplantation patients and the non-affected lung of lung cancer patients (control groups) hardly induced any processing of CXCL12. In COVID-19 BAL fluids with high proteolytic activity, processing occurred exclusively NH2-terminally and was predominantly mediated by neutrophil elastase. In low proteolytic activity BAL fluid and plasma samples, NH2- and COOH-terminal proteolysis by CD26 and carboxypeptidases were observed. Finally, protease inhibitors already approved for clinical use such as sitagliptin and sivelestat prevented CXCL12 processing and may therefore be of pharmacological interest to prolong CXCL12 half-life and biological activity in vivo.

Biased action of the CXCR4-targeting drug plerixafor is essential for its superior hematopoietic stem cell mobilization

Following the FDA-approval of the hematopoietic stem cell (HSC) mobilizer plerixafor, orally available and potent CXCR4 antagonists were pursued. One such proposition was AMD11070, which was orally active and had superior antagonism in vitro; however, it did not appear as effective for HSC mobilization in vivo. Here we show that while AMD11070 acts as a full antagonist, plerixafor acts biased by stimulating β-arrestin recruitment while fully antagonizing G protein. Consequently, while AMD11070 prevents the constitutive receptor internalization, plerixafor allows it and thereby decreases receptor expression. These findings are confirmed by the successful transfer of both ligands' binding sites and action to the related CXCR3 receptor. In vivo, plerixafor exhibits superior HSC mobilization associated with a dramatic reversal of the CXCL12 gradient across the bone marrow endothelium, which is not seen for AMD11070. We propose that the biased action of plerixafor is central for its superior therapeutic effect in HSC mobilization.

Concurrent Comparison of the Prognostic Values of Tumor Budding, Tumor Stroma Ratio, Tumor Infiltrating Pattern and Lymphocyte-to-Monocyte Ratio in Colorectal Cancer Patients

Objectives: Tumor budding (TB), tumor stroma ratio (TSR), tumor infiltrating pattern (TIP), and preoperative lymphocyte-to-monocyte ratio (LMR) were previously reported to be useful prognostic factors in colorectal cancer (CRC); however, the correlation among these markers and their individual prognostic potency have not been extensively studied. Methods: A cohort of 147 stage I-IV CRC patients was obtained retrospectively, and the patients were divided into subgroups based on low or high TB/TSR/LMR, TIPa (expansile + intermediate) and TIPb (infiltrative) values. The differences in relapse-free survival (RFS) and overall survival (OS) intervals among these subgroups were determined by Kaplan-Meier analysis followed by log-rank tests. The Cox proportional hazard model was applied for the univariate and multivariate analysis of RFS and OS rates. Results:TB, TIP, and LMR, but not TSR, are useful markers for predicting patient survival. Patients with a poor histological grade and large tumor diameter were more likely to present with high TB, TIPb, and low LMR values; in addition, those with advanced T, N, and TNM stages and elevated preoperative CA199 levels had high TB and TIPb levels. TB, TIP, and LMR were significant prognostic factors for the RFS (TB: HR [hazard ratio] = 2.28, 95% CI = 1.30-4.00, P < .01; TIP: HR = 2.60, 95% CI = 1.46-4.60, P < .01; LMR: HR = 0.79, 95% CI = 0.65-0.96, P = .02) and OS (TB: HR = 2.43, 95% CI = 1.32-4.48, P < .01; TIP: HR = 2.49, 95% CI = 1.34-4.63, P < .01; LMR: HR = 0.79, 95% CI = 0.64-0.98, P = .03) intervals. In addition, TB and LMR were independent prognostic factors for the RFS interval (TB: HR = 1.80, 95% CI = 1.01-3.19, P = .05; LMR: HR = 0.80, 95% CI = 0.67-0.96, P = .01), but only LMR was an independent factor for OS rates (HR = 0.80, 95% CI = 0.65-0.98, P = .03). Conclusion: Although TB, TIP, and LMR are useful prognostic markers for CRC, the LMR is likely to be the only independent prognostic factor for both RFS and OS outcomes in practice.

Pathological roles of the homeostatic chemokine CXCL12

CXCL12 is a CXC chemokine that traditionally has been classified as a homeostatic chemokine. It contributes to physiological processes such as embryogenesis, hematopoiesis and angiogenesis. In contrast to these homeostatic functions, increased expression of CXCL12 in general, or of a specific CXCL12 splicing variant has been demonstrated in various pathologies. In addition to this increased or differential transcription of CXCL12, also upregulation of its receptors CXC chemokine receptor 4 (CXCR4) and atypical chemokine receptor 3 (ACKR3) contributes to the onset or progression of diseases. Moreover, posttranslational modification of CXCL12 during disease progression, through interaction with locally produced molecules or enzymes, also affects CXCL12 activity, adding further complexity. As CXCL12, CXCR4 and ACKR3 are broadly expressed, the number of pathologies wherein CXCL12 is involved is growing. In this review, the role of the CXCL12/CXCR4/ACKR3 axis will be discussed for the most prevalent pathologies. Administration of CXCL12-neutralizing antibodies or small-molecule antagonists of CXCR4 or ACKR3 delays disease onset or prevents disease progression in cancer, viral infections, inflammatory bowel diseases, rheumatoid arthritis and osteoarthritis, asthma and acute lung injury, amyotrophic lateral sclerosis and WHIM syndrome. On the other hand, CXCL12 has protective properties in Alzheimer's disease and multiple sclerosis, has a beneficial role in wound healing and has crucial homeostatic properties in general.