Circular RNA Cdr1as inhibits proliferation and delays injury-induced regeneration of the intestinal epithelium

Circular RNAs (circRNAs) are highly expressed in the mammalian intestinal epithelium, but their functions remain largely unknown. Here, we identified the circRNA Cdr1as as a repressor of intestinal epithelial regeneration and defense. Cdr1as levels increased in mouse intestinal mucosa after colitis and septic stress, as well as in human intestinal mucosa from patients with inflammatory bowel disease and sepsis. Ablation of the Cdr1as locus from the mouse genome enhanced renewal of the intestinal mucosa, promoted injury-induced epithelial regeneration, and protected the mucosa against colitis. We found approximately 40 microRNAs, including miR-195, differentially expressed between intestinal mucosa of Cdr1as-knockout (Cdr1as-/-) versus littermate mice. Increasing the levels of Cdr1as inhibited intestinal epithelial repair after wounding in cultured cells and repressed growth of intestinal organoids cultured ex vivo, but this inhibition was abolished by miR-195 silencing. The reduction in miR-195 levels in the Cdr1as-/- intestinal epithelium was the result of reduced stability and processing of the precursor miR-195. These findings indicate that Cdr1as reduces proliferation and repair of the intestinal epithelium at least in part via interaction with miR-195 and highlight a role for induced Cdr1as in the pathogenesis of unhealed wounds and disrupted renewal of the intestinal mucosa.

Lymphotactin expression by engineered myeloma cells drives tumor regression: mediation by CD4+ and CD8+ T cells and neutrophils expressing XCR1 receptor

The C chemokine lymphotactin has been characterized as a T cell chemoattractant both in vitro and in vivo. To determine whether lymphotactin expression within tumors could influence tumor growth, we transfected an expression vector for lymphotactin into SP2/0 myeloma cells and tested their ability to form tumors in BALB/c and nude mice. Transfection did not alter cell growth in vitro. Whereas SP2/0 cells gave rise to a 100% tumor incidence, lymphotactin-expressing SP2/0-Lptn tumors invariably regressed in BALB/c mice and became infiltrated with CD4(+) and CD8(+) T cells and neutrophils. Regression of the SP2/0-Lptn tumors was associated with a type 1 cytokine response and dependent on both CD4(+) and CD8(+) T cells, but not NK cells. Both SP2/0 and SP2/0-Lptn tumors grew in nude mice, but growth of the latter tumors was retarded and associated with heavy neutrophil responses; this retardation of SP2/0-Lptn tumor growth was reversed by neutrophil depletion of the mice. Our data also indicate that mouse neutrophils express the lymphotactin receptor XCR1 and that lymphotactin specifically chemoattracts these cells in vitro. Thus, lymphotactin has natural adjuvant activities that may augment antitumor responses via effects on both T cells and neutrophils and thereby could be important in gene transfer immunotherapies for some cancers.

Neutrophils and B cells express XCR1 receptor and chemotactically respond to lymphotactin

The C chemokine lymphotactin (Lptn) has been reported to act specifically on CD4(+) and CD8(+) T lymphocytes and natural killer (NK) cells, but not monocytes. However, the chemotactic effect of Lptn on other types of hematopoietic cells has not been well studied. In this study we investigated (i) the chemotactic influences of Lptn on T and B lymphocytes, neutrophils, monocytes, and dendritic cells, and (ii) the expression of the Lptn receptor (XCR1) by these cells, using RT-PCR. Our data showed that Lptn is chemotactic for B lymphocytes and neutrophils as well as T lymphocytes, but not for monocytes or dendritic cells, and that XCR1 expression is found only in association with T and B lymphocytes and neutrophils, but not monocytes or dendritic cells. Thus, this study is the first demonstration of a chemotactic effect of Lptn on neutrophils and confirms the association of this effect with expression of the XCR1 receptor on these cells. These data suggest that Lptn could potentially be an important protein in the regulation of T and B lymphocytes and neutrophil trafficking, and thereby also their roles in inflammatory and immunological responses.