Xiaoting Tang

Triggering receptor expressed on myeloid cells (TREM)-1 is an orphan receptor implicated in innate immune activation. Inhibition of TREM-1 reduces sepsis in mouse models, suggesting a role for it in immune responses triggered by bacteria. However, the absence of an identified ligand has hampered a full understanding of TREM-1 function. We identified complexes between peptidoglycan recognition protein 1 (PGLYRP1) and bacterially derived peptidoglycan that constitute a potent ligand capable of binding TREM-1 and inducing known TREM-1 functions. Interestingly, multimerization of PGLYRP1 bypassed the need for peptidoglycan in TREM-1 activation, demonstrating that the PGLYRP1/TREM-1 axis can be activated in the absence of bacterial products. The role for PGLYRP1 as a TREM-1 activator provides a new mechanism by which bacteria can trigger myeloid cells, linking two known, but previously unrelated, pathways in innate immunity.

Impaired intestinal barrier plays an important role in the pathogenesis of hypertension primarily through promoting the development of chronic low-grade inflammation. Baicalin is the major flavonoid component of Scutellaria baicalensis Georgi, a medicinal plant commonly used for the treatment of inflammatory intestinal disorders and hypertension in traditional Chinese medicine. However, it remains to be elucidated whether baicalin alleviates hypertension-associated intestinal barrier impairment. The current study thus investigated the effects of baicalin on the intestinal barrier integrity, the intestinal expression of genes encoding proinflammatory factors and tight junction proteins, the serum levels of the inflammatory markers, the amount of fecal short-chain fatty acids (SCFAs) and the abundance of SCFAs-producing bacteria in the spontaneously hypertensive rats (SHRs). The results showed that baicalin alleviated the pathological lesions in the ilium and the proximal colon in the SHRs. Baicalin treatment resulted in decreased ileal and colonic expression of proinflammatory genes in the SHRs. In addition, baicalin treatment attenuated hypertension-associated intestinal hyperpermeability and decreased the serum levels of inflammatory indicators such as hs-CRP, IL-1β and IL-6 in the SHRs. The protective effect of baicalin on the intestinal integrity was also supported by well-preserved intestinal ultrastructure and increased intestinal expression of genes encoding tight junction proteins such as ZO-1, cingulin and occludin in the SHRs. Lastly, baicalin treatment increased the amount of fecal SCFAs and the abundance of SCFAs-producing bacteria in the SHRs. In conclusion, the work here provides for the first time the morphological, biochemical and molecular evidence supporting the protective effects of baicalin on the intestinal integrity in the SHRs, which may help better understand the therapeutic effects of Scutellaria baicalensis Georgi in the treatment of hypertension.

Campylobacter jejuni is one of the leading bacterial causes of food-borne gastroenteritis. Infection with C. jejuni is frequently acquired through the consumption of undercooked poultry or foods cross-contaminated with raw poultry. Given the importance of poultry as a reservoir for Campylobacter organisms, investigators have performed studies to understand the protective role of maternal antibodies in the ecology of Campylobacter colonization of poultry. In a previous study, chicks with maternal antibodies generated against the S3B strain of C. jejuni provided protection against Campylobacter colonization (O. Sahin, N. Luo, S. Huang, and Q. Zhang, Appl. Environ. Microbiol. 69:5372-5379, 2003). We obtained serum samples, collectively referred to as the C. jejuni S3B-SPF sera, from the previous study. These sera were determined to contain maternal antibodies that reacted against C. jejuni whole-cell lysates as judged by enzyme-linked immunosorbent assay. The antigens recognized by the C. jejuni S3B-SPF antibodies were identified by immunoblot analysis, coupled with mass spectrometry, of C. jejuni outer membrane protein extracts. This approach led to the identification of C. jejuni proteins recognized by the maternal antibodies, including the flagellin proteins and CadF adhesin. In vitro assays revealed that the C. jejuni S3B-SPF sera retarded the motility of the C. jejuni S3B homologous strain but did not retard the motility of a heterologous strain of C. jejuni (81-176). This finding provides a possible mechanism explaining why maternal antibodies confer enhanced protection against challenge with a homologous strain compared to a heterologous strain. Collectively, this study provides a list of C. jejuni proteins against which protective antibodies are generated in hens and passed to chicks.

The membrane proteome plays a critical role in electron transport processes in Shewanella oneidensis MR-1, a bacterial organism that has great potential for bioremediation. Biotinylation of intact cells with subsequent affinity-enrichment has become a useful tool for characterization of the membrane proteome. As opposed to these commonly used, water-soluble commercial reagents, we here introduce a family of hydrophobic, cell-permeable affinity probes for extensive labeling and detection of membrane proteins. When applied to S. oneidensis cells, all three new chemical probes allowed identification of a substantial proportion of membrane proteins from total cell lysate without the use of specific membrane isolation method. From a total of 410 unique proteins identified, approximately 42% are cell envelope proteins that include outer membrane, periplasmic, and inner membrane proteins. This report demonstrates the first application of this intact cell biotinylation method to S. oneidensis and presents the results of many identified proteins that are involved in metal reduction processes. As a general labeling method, all chemical probes we introduced in this study can be extended to other organisms or cell types and will help expedite the characterization of membrane proteomes.

Intestinal pathophysiological alterations have recently been revealed to be implicated in the pathogenesis of hypertension, necessitating further investigations to better understand the intestinal effects of anti-hypertensive drugs. The current study thus investigated the pharmacological implications of a commonly used first-line angiotensin II type 1 receptor blocker, candesartan cilexetil, on the intestinal barrier impairment and gut dysbiosis in spontaneously hypertensive rats (SHRs). The results revealed that candesartan treatment protected against ileal and colonic pathologies and increased the intestinal expression of genes encoding tight junction proteins such as cingulin, occludin and tight junction protein 1 in SHRs. Serum level of lipopolysaccharides-binding protein was increased in candesartan-treated SHRs, supporting the notion that candesartan treatment provided protection against hypertension-associated impairment of intestinal barrier. Candesartan treatment also increased the amount of fecal short-chain fatty acids (SCFAs) including acetic acid, propionic acid, and butyric acid in SHRs. Fecal 16S rDNA sequencing further revealed that candesartan treatment normalized hypertension-altered ratio of Firmicutes to Bacteroidetes in SHRs. Most notably, candesartan treatment counteracted hypertension-associated diminishment of lactic acid-producing genus Lactobacillus. Taken together, the current study demonstrates for the first time that candesartan treatment alleviates hypertension-associated pathophysiological alterations in the gut, increases microbial production of SCFAs and preserves gut Lactobacillus under hypertensive conditions, which sheds novel light on the pharmacological implications of candesartan in the treatment of hypertension.