A310 helical turn is essential for the proliferation-inhibiting properties of macrophage inflammatory protein-1 alpha (CCL3)

Relation between macrophage inflammatory protein-1 and intercellular adhesion molecule-1 and computed tomography findings in critically-ill saudi covid-19 patients

BACKGROUND

Several, clinical and biochemical factors were suggested as risk factors for more severe forms of Covid-19. Macrophage inflammatory protein-1 alpha (MIP-1α, CCL3) is a chemokine mainly involved in cell adhesion and migration. Intracellular adhesion molecule 1 (ICAM-1) is an inducible cell adhesion molecule involved in multiple immune processes. The present study aimed to assess the relationship between baseline serum MIP-1α and ICAM-1 level in critically-ill Covid-19 patients and the severity of computed tomography (CT) findings.

METHODS

The study included 100 consecutive critically-ill patients with Covid-19 infection. Diagnosis of infection was established on the basis of RT-PCR tests. Serum MIP-1α and ICAM-1 levels were assessed using commercially available ELISA kits. All patients were subjected to a high-resolution computed tomography assessment.

RESULTS

According to the computed tomography severity score, patients were classified into those with moderate/severe (n=49) and mild (n = 51) pulmonary involvement. Severe involvement was associated with significantly higher MIP-1α and ICAM-1 level. Correlation analysis identified significant positive correlations between MIP-1α and age, D-dimer, IL6, in contrast, there was an inverse correlation with INF-alpha. Additionally, ICAM-1 showed significant positive correlations with age, D-Dimer,- TNF-α, IL6,while an inverse correlation with INF-alpha was observed.

CONCLUSIONS

MIP-1α and ICAM-1 level are related to CT radiological severity in Covid-19 patients. Moreover, these markers are well-correlated with other inflammatory markers suggesting that they can be used as reliable prognostic markers in Covid-19 patients.

Identification of a conserved chemokine receptor motif that enables ligand discrimination

Extensive ligand-receptor promiscuity in the chemokine signaling system balances beneficial redundancy and specificity. However, this feature poses a major challenge to selectively modulate the system pharmacologically. Here, we identified a conserved cluster of three aromatic receptor residues that anchors the second extracellular loop (ECL2) to the top of receptor transmembrane helices (TM) 4 and 5 and enables recognition of both shared and specific characteristics of interacting chemokines. This cluster was essential for the activation of several chemokine receptors. Furthermore, characteristic motifs of the ß₁ strand and 30s loop make the two main CC-chemokine subgroups-the macrophage inflammatory proteins (MIPs) and monocyte chemoattractant proteins (MCPs)-differentially dependent on this cluster in the promiscuous receptors CCR1, CCR2, and CCR5. The cluster additionally enabled CCR1 and CCR5 to discriminate between closely related MIPs based on the N terminus of the chemokine. G protein signaling and β-arrestin2 recruitment assays confirmed the importance of the conserved cluster in receptor discrimination of chemokine ligands. This extracellular site may facilitate the development of chemokine-related therapeutics.

A mini review on immune role of chemokines and its receptors in snakehead murrel Channa striatus

Chemokines are ubiquitous cytokine molecules involved in migration of cells during inflammation and normal physiological processes. Though the study on chemokines in mammalian species like humans have been extensively studied, characterization of chemokines in teleost fishes is still in the early stage. The present review provides an overview of chemokines and its receptors in a teleost fish, Channa striatus. C. striatus is an air breathing freshwater carnivore, which has enormous economic importance. This species is affected by an oomycete fungus, Aphanomyces invadans and a Gram negative bacteria Aeromonas hydrophila is known to cause secondary infection. These pathogens impose immune changes in the host organism, which in turn mounts several immune responses. Of these, the role of cytokines in the immune response is immense, due to their involvement in several activities of inflammation such as cell trafficking to the site of inflammation and antigen presentation. Given that importance, chemokines in fishes do have significant role in the immunological and other physiological functions of the organism, hence there is a need to understand the characteristics, activities and performace of these small molecules in details.

Fish chemokines 14, 20 and 25: A comparative statement on computational analysis and mRNA regulation upon pathogenic infection

In this study, we reported a molecular characterization of three CC chemokines namely, CsCC-Chem14, CsCC-Chem20 and CsCC-Chem25 which are were identified from the established cDNA library of striped murrel Channa striatus. Multiple sequence alignment of all the three chemokines revealed the presence of gene specific domains and motifs including small cytokine domain, IL8 like domain, receptor binding site and glycosaminoglycan (GAG) binding sites. Three dimensional structures of the chemokines under study showed an important facet on their anti-microbial property. Tissue specific mRNA expression showed that the CsCC-Chem14 is highly expressed in spleen, CsCC-Chem20 in liver and CsCC-Chem25 in trunk kidney. On challenge C. striatus with oomycete fungus Aphanomyces invadans, both CsCC-Chem20 and CsCC-Chem25 showed significant (P < 0.05) up-regulation compared to CsCC-Chem14. The increase in the expression levels of CsCC-Chem20 and CsCC-Chem25 due to infection showed that they are antimicrobial proteins. But considering the CsCC-Chem14 expression, it is found to be a constitutive chemokine and is involved in homeostatic function in spleen of C. striatus. C. striatus challenged with bacteria Aeromonas hydrophila also exhibited different up-regulation pattern in all the three chemokines at various time points. However, extensive studies are required to determine the functional activities of CsCC-Chem14, CsCC-Chem20 and CsCC-Chem25 in vitro and in vivo to gain more knowledge at the molecular and proteomic levels.

Hypercholesterolemia links hematopoiesis with atherosclerosis

Atherosclerosis is characterized by the progressive accumulation of lipids and leukocytes in the arterial wall. Leukocytes such as macrophages accumulate oxidized lipoproteins in the growing atheromata and give rise to foam cells, which can then contribute to the necrotic core of lesions. Lipids and leukocytes also interact in other important ways. In experimental models, systemic hypercholesterolemia is associated with severe neutrophilia and monocytosis. Recent evidence indicates that cholesterol-sensing pathways control the proliferation of hematopoietic stem-cell progenitors. Here we review some of the studies that are forging this particular link between metabolism and inflammation, and propose several strategies that could target this axis for the treatment of cardiovascular disease.

Co-culture of hematopoietic stem/progenitor cells with human osteblasts favours mono/macrophage differentiation at the expense of the erythroid lineage

Hematopoietic stem cells (HSCs) are located in the bone marrow in a specific microenvironment referred as the hematopoietic stem cell niche, where HSCs interact with a variety of stromal cells. Though several components of the stem cell niche have been identified, the regulatory mechanisms through which such components regulate the stem cell fate are still unknown. In order to address this issue, we investigated how osteoblasts (OBs) can affect the molecular and functional phenotype of Hematopoietic Stem/Progenitor Cells (HSPCs) and vice versa. For this purpose, human CD34+ cells were cultured in direct contact with primary human OBs. Our data showed that CD34+ cells cultured with OBs give rise to higher total cell numbers, produce more CFUs and maintain a higher percentage of CD34+CD38- cells compared to control culture. Moreover, clonogenic assay and long-term culture results showed that co-culture with OBs induces a strong increase in mono/macrophage precursors coupled to a decrease in the erythroid ones. Finally, gene expression profiling (GEP) allowed us to study which signalling pathways were activated in the hematopoietic cell fraction and in the stromal cell compartment after coculture. Such analysis allowed us to identify several cytokine-receptor networks, such as WNT pathway, and transcription factors, as TWIST1 and FOXC1, that could be activated by co-culture with OBs and could be responsible for the biological effects reported above. Altogether our results indicate that OBs are able to affect HPSCs on 2 different levels: on one side, they increase the immature progenitor pool in vitro, on the other side, they favor the expansion of the mono/macrophage precursors at the expense of the erythroid lineage.

3D profile-based approach to proteome-wide discovery of novel human chemokines

Chemokines are small secreted proteins with important roles in immune responses. They consist of a conserved three-dimensional (3D) structure, so-called IL8-like chemokine fold, which is supported by disulfide bridges characteristic of this protein family. Sequence- and profile-based computational methods have been proficient in discovering novel chemokines by making use of their sequence-conserved cysteine patterns. However, it has been recently shown that some chemokines escaped annotation by these methods due to low sequence similarity to known chemokines and to different arrangement of cysteines in sequence and in 3D. Innovative methods overcoming the limitations of current techniques may allow the discovery of new remote homologs in the still functionally uncharacterized fraction of the human genome. We report a novel computational approach for proteome-wide identification of remote homologs of the chemokine family that uses fold recognition techniques in combination with a scaffold-based automatic mapping of disulfide bonds to define a 3D profile of the chemokine protein family. By applying our methodology to all currently uncharacterized human protein sequences, we have discovered two novel proteins that, without having significant sequence similarity to known chemokines or characteristic cysteine patterns, show strong structural resemblance to known anti-HIV chemokines. Detailed computational analysis and experimental structural investigations based on mass spectrometry and circular dichroism support our structural predictions and highlight several other chemokine-like features. The results obtained support their functional annotation as putative novel chemokines and encourage further experimental characterization. The identification of remote homologs of human chemokines may provide new insights into the molecular mechanisms causing pathologies such as cancer or AIDS, and may contribute to the development of novel treatments. Besides, the genome-wide applicability of our methodology based on 3D protein family profiles may open up new possibilities for improving and accelerating protein function annotation processes.

The chemokine network in acute myelogenous leukemia: molecular mechanisms involved in leukemogenesis and therapeutic implications

Acute myelogenous leukemia (AML) is a bone marrow disease in which the leukemic cells show constitutive release of a wide range of CCL and CXCL chemokines and express several chemokine receptors. The AML cell release of various chemokines is often correlated and three release clusters have been identified: CCL2-4/CXCL1/8, CCL5/CXCL9-11, and CCL13/17/22/24/CXCL5. CXCL8 is the chemokine usually released at highest levels. Based on their overall constitutive release profile, patients can be classified into distinct subsets that differ in their T cell chemotaxis towards the leukemic cells. The release profile is modified by hypoxia, differentiation status, pharmacological interventions, and T cell cytokine responses. The best investigated single chemokine in AML is CXCL12 that binds to CXCR4. CXCL12/CXCR4 is important in leukemogenesis through regulation of AML cell migration, and CXCR4 expression is an adverse prognostic factor for patient survival after chemotherapy. Even though AML cells usually release high levels of several chemokines, there is no general increase of serum chemokine levels in these patients and the levels are also influenced by patient age, disease status, chemotherapy regimen, and complicating infections. However, serum CXCL8 levels seem to partly reflect the leukemic cell burden in AML. Specific chemokine inhibitors are currently being developed, although redundancy and pleiotropy of the chemokine system are obstacles in drug development.

Identification of new variants within the two functional genes CCL3 and CCL3L encoding the CCL3 (MIP-1alpha) chemokine: implications for HIV-1 infection

The CC chemokine CCL3 is encoded by two functional genes, namely CCL3 and CCL3L, and has been identified as a key chemokine in HIV-1 susceptibility and disease progression. The complete CCL3 and CCL3L genes and core promoters of 43 African mother-infant pairs (86 samples) and 28 Caucasian adults in South Africa were sequenced and extensively analysed for genetic variations. Africans were found to be more polymorphic in both genes with 25 single nucleotide polymorphisms (SNPs) in the CCL3 gene and 14 gene copy number single nucleotide polymorphisms (gcnSNPs) in the CCL3L gene, compared to nine CCL3 SNPs and eight CCL3L gcnSNPs in Caucasians. A total of 14 polymorphisms across the two genes were newly identified in this study, most (12/14) of which were exclusive to the African population. In addition, two indels were identified and characterized in the CCL3 and CCL3L genes of a small number of individuals. Of the numerous unique intragenic haplotypes found in the two genes, none were shared by the two population groups. A newly identified five-SNP CCL3 haplotype (Hap-C1) found in a high frequency in Caucasians, however, seems to be evolutionarily related to the most prevalent newly identified African seven-SNP CCL3 haplotype (Hap-A1). Hap-A1 also includes an SNP in the core promoter region and previous CCL3 haplotypes that have been reported to be associated with HIV-1 infection appear to be smaller haplotypes within Hap-A1. We thus propose Hap-A1 as a likely candidate for influencing levels of CCL3 production and in turn outcomes of HIV-1 infection.