Molecular Identification and Dual Functions of Two Different CXC Chemokines in Nile Tilapia (Oreochromis niloticus) against Streptococcus agalactiae and Flavobacterium columnare

Abstract

Two CXC chemokines in Nile tilapia (On-CXC1 and On-CXC2) were identified at both the genomic and proteomic levels. A southern blot analysis and comparison searching in Ensembl confirmed the typical structure of the CXC chemokine genes and provided evidence for unusual mechanisms used to generate the two different CXC chemokine transcripts that have not been reported in other vertebrate species so far. The expression levels of On-CXC1 and On-CXC2 were analyzed by quantitative real-time PCR. These two mRNAs were detected in various tissues of normal Nile tilapia, especially in the spleen, heart, and head kidney, indicating a homeostatic function in immunosurveillance. A time-course experiment clearly demonstrated that these two transcripts were effectively enhanced in the head kidney, spleen and trunk kidney of Nile tilapia 6, 12 and 24 h after injection with Streptococcus agalactiae but were down-regulated in all tested tissues at 48 h, reflecting the fact that they have short half-lives during the crucial response to pathogens that is characteristic of CXC chemokine genes in other vertebrates. Functional analyses obviously exhibited that these two CXC chemokines at concentrations of 1–10 μg strongly inactivated S. agalactiae and Flavobacterium columnare and effectively induced phagocytosis of leukocytes in vitro.

Identification, Expression and Antimicrobial Functional Analysis of Interleukin-8 (IL-8) in Response to <em>Streptococcus iniae</em> and Flavobacterium Covae in Asian Seabass (Lates calcarifer Bloch, 1790)

“…The highest PA level was observed in the experimental group treated with 100 µg of purified protein, demonstrating the effectiveness of all rLcIL-8 concentrations in enhancing in vitro phagocytic activity. These results are consistent with the findings of a previous report [58], demonstrating that cells treated with 1 and 10 µg/mL rOn-CXC1 and rOn-CXC2 significantly enhance the PA of PBLs in Nile tilapia. Additionally, the experimental group treated with 10 µg/mL of both rOn-CXC1 and rOn-CXC2 exhibited the highest level of PI.…”

“…Based on dose-dependent induction, it was observed that the highest concentration of both bacterial solutions strongly induced LcIL-8 mRNA, followed by the moderate dose, while the lower concentration showed weaker induction. Similar results were observed in Nile tilapia after being induced with the highest dose of 1×10 9 CFU/mL S. agalactiae, which potentially stimulated CXC chemokine expression compared to lower concentrations of pathogenic bacteria [58]. These findings suggest that a higher bacterial concentration can enhance their ability to effectively spread, colonize, and invade host cells and tissues [59], which are considered one of the primary factors leading to disease in the host.…”

Identification, Expression and Antimicrobial Functional Analysis of Interleukin-8 (IL-8) in Response to Streptococcus iniae and Flavobacterium covae in Asian Seabass (Lates calcarifer Bloch, 1790)

“…The highest PA level was observed in the treatment group that obtained 100 µg of rLcIL-8, demonstrating the effectiveness of all the rLcIL-8 concentrations in enhancing in vitro phagocytic activity. This obtained information is similar to the previous findings [62], demonstrating that phagocytes exposed to rOn-CXC1 and rOn-CXC2 at 1 and 10 µg/mL significantly enhance the PA of PBLs in Nile tilapia. Additionally, the treatment group that obtained 10 µg/mL of both rOn-CXC1 and rOn-CXC2 exhibited the highest level of PI.…”

“…Based on dose-dependent induction, it was observed that the highest concentration of both bacterial solutions strongly induced LcIL-8 mRNA, followed by the moderate dose, while the lower concentration showed weaker induction. Similar results were observed in Nile tilapia after being induced with the highest dose of 1 × 10 9 CFU/mL S. agalactiae, which potentially stimulated the expression of CXC chemokine correlated to lower bacterial concentrations [62]. These findings suggest that a higher bacterial concentration can enhance their ability to effectively spread, colonize, and invade host cells and tissues [63], which are together considered one of the primary factors leading to disease in the host.…”

Chemokine CCL21 determines immunotherapy response in hepatocellular carcinoma by affecting neutrophil polarization

“…Chemokines are defined as a superfamily of cytokines with chemotactic and pro-inflammatory properties that induce directed chemotaxis and regulate immune cell migration during inflammatory responses [ 6 ]. Numerous studies have shown that chemokine levels are highly correlated with tumor progression, tumor immune response, and prognosis.…”