Rohwer, N. | Search bioRxiv

bioRxiv2024

Ex vivo DHA supplementation suppresses prostaglandin E2 formation in primary human macrophages

ScopeThere is evidence that intake of long-chain n-3 polyunsaturated fatty acids (PUFA) is associated with improved prognosis for inflammatory diseases. However, the underlying mechanisms are still subject of ongoing research. For this purpose, we developed an ex vivo n-3 PUFA supplementation strategy to test n-3 PUFA supplementation under controlled conditions in primary human macrophages. Methods and resultsCells were supplemented with docosahexaenoic acid (DHA). Quality parameters to account for possible confounders were established for a reproducible and reliable supplementation. Following supplementation, PUFA pattern of cells was shifted towards a pattern reflecting that of subjects with a high n-3 PUFA status. This was accompanied by a decrease of arachidonic acid-derived oxylipins in a dose- and time-dependent manner in favor of n-3 PUFA ones. Stimulation with LPS resulted in decreased levels of pro-inflammatory prostaglandins in the DHA-supplemented cells, but no changes in cytokines. ConclusionIn vitro supplementation studies with n-3 PUFA need rigorous controls to exclude background formation of oxylipins. By accounting for these possible confounders the desribed ex vivo approach is a promising tool for the mechanistic investigation of n-3 PUFA in primary human immune cells, offering an alternative for intervention studies in humans.

physiology↗

bioRxiv2018

Non-canonical HIF-1 stabilization is essential for intestinal tumorigenesis

The hypoxia-inducible transcription factor HIF-1 is appreciated as a promising target for cancer therapy. However, conditional deletion of HIF-1 and HIF-1 target genes in cells of the tumor microenvironment can result in accelerated tumor growth, calling for a detailed characterization of the cellular context to fully comprehend HIF-1s role in tumorigenesis. We dissected cell type-specific functions of HIF-1 for intestinal tumorigenesis by lineage-restricted deletion of the Hif1a locus. Intestinal epithelial cell-specific Hif1a loss reduced activation of wnt/{beta}-catenin, tumor-specific metabolism and inflammation, significantly inhibiting tumor growth. Deletion of Hif1a in myeloid cells reduced the expression of fibroblast-activating factors in tumor-associated macrophages resulting in decreased abundance of tumor-associated fibroblasts and robustly reduced tumor formation. Interestingly, hypoxia was detectable only sparsely and without spatial association with nuclear HIF-1 in intestinal adenomas, pointing towards a functional importance of hypoxia-independent, i.e. non-canonical HIF-1 stabilization that has not been previously appreciated. This adds a further layer of complexity to the regulation of HIF-1 and suggests that hypoxia and HIF-1 stabilization can be uncoupled in cancer. Collectively, our data show that HIF-1 is a pivotal pro-tumorigenic factor for intestinal tumor formation, controlling key oncogenic programs in both the epithelial tumor compartment and the tumor microenvironment.

cancer biology↗