IL-8/CXCL8 Protein, Human (72a.a)

IL-8 (CXCL8) belongs to the ELR⁺ CXC chemokines family. IL-8 is initially produced as a protein of 99 amino acids that undergoes cleavage to form active IL-8 isoforms, a 77 amino acid peptide in non-immune cells or a 72 amino acid peptide in monocytes and macrophages. The gene encoding IL-8 is located on chromosome 4q13-q21. Dimerisation of IL-8 forms the structural basis for receptor binding. IL-8 is expressed by various cells including monocytes, macrophages, leukocytes, endothelial cells, and epithelial cells^[1][2][3].
Mature human IL-8/CXCL8 shares 75% amino acid sequence identity with canine IL-8/CXCL8. While, human IL-8 shares 94.95% aa sequence identity with Rhesus Macaque IL-8 protein.
IL-8 is responsible for the recruitment and activation of neutrophils and granulocytes to the site of inflammation. IL-8 is almost undetectable in physiological states, but is rapidly induced by pro-inflammatory cytokines such as TNFα and IL-1β. The function of IL-8 mainly relies on its interaction with specific cell surface GPCR, CXCR1 and CXCR2. In addition, IL-8 is reported to promote integrin β3 upregulation and the invasion of hepatocellular carcinoma cells through activation of the PI3K/Akt pathway. In odontogenic lesions, IL-8 has been proven to be highly expressed in ameloblastoma epithelial cells and irreversible pulpitis. In rheumatoid arthritis and other inflammatory joint diseases IL-8 could bring about the accumulation of neutrophils, which are considered a major source of cartilage-degrading enzymes. IL-8 stimulates the MAPK and tyrosine phosphorylation of cellular proteins. Tumour cells and fibroblasts communicate with each other, including autocrine and paracrine factors, including IL-8, resulting in the upregulation of MMP2 and MMP9 degradable extracellular matrix (ECM) components that trigger tumour invasion^[1][2][3][4].
  IL-8 is typically known to promote angiogenesis, but it also activates matrix metalloproteinase (MMP) that is involved in metastasisrelated tissue remodelling. IL-8 is induced in lipopolysaccharide (LPS)-stimulated monocytes and shown to induce neutrophil migration. IL-8 exerts multiple effects on biological activities of tumour cells including proliferation, invasion and migration. IL-8 also increases the expression of Akt in androgen-independent prostate cancer (AIPC) cell lines. IL-8 activates MAPK signalling via PI3K in neutrophils, and via transactivation of EGFR resulting in Ras-GTPase activation in ovarian and lung cancer cell lines. There is substantial amount of experimental data suggesting that IL-8 and receptors contribute to elimination of pathogens, but may also contribute significantly to disease-associated processes, including tissue injury, fibrosis, angiogenesis and tumorigenesis^[3][5].

Recombinant human IL-8 (10, 30, and 100 μg/kg; single intravenous injection) injected into rhesus monkeys (2-3 years; 2.5-4.5 kg). IL-8 injection results in instant neutropenia that was due to pulmonary sequestration. Within 30 minutes after IL-8 injection, neutrophilia developed with counts up to 10-fold greater than baseline levels. The numbers of hematopoietic progenitor cells (HPCs) increased of blood at 30 minutes after injection of 100 μg/kg IL-8^[7].

Recombinant human IL-8/CXCL8 (100 ng/mL; for 24-96 h) stimulation leads to enhancement of invasion and suppression of late stage apoptosis in MG-63 cells. Moreover, secretions of MMPs by MG-63 cells are also increased upon stimulation. CXCL8 induces the elevations of phosphorylated PI3K and Akt, but not PKC or FAK^[6].