Impaired butyrate absorption in the proximal colon, low serum butyrate and diminished central effects of butyrate on blood pressure in spontaneously hypertensive rats

AIM

Butyrate is a major gut microbiota-derived metabolite. Reduced butyrate-producing bacteria has been reported in the spontaneously hypertensive rat (SHR), a model of hypertension characterized by dysfunctional autonomic nervous system and gut dysbiosis. Here, we demonstrate a potential mechanism for butyrate in blood pressure regulation.

METHODS

High-performance liquid chromatography and liquid chromatography-mass spectrometry were performed to measure butyrate levels in feces and serum. Ussing chamber determined butyrate transport in colon ex vivo. Real-time PCR and immunohistochemistry evaluated expression of butyrate transporter, Slc5a8, in the colon. Mean arterial blood pressure was measured in catheterized anesthetized rats before and after a single butyrate intracerebroventricular injection. Activity of cardioregulatory brain regions was determined by functional magnetic resonance imaging to derive neural effects of butyrate.

RESULTS

In the SHR, we demonstrated elevated butyrate levels in cecal content, but diminished butyrate levels in circulation, possibly due to reduced expression of Slc5a8 transporter in the colon. In addition, we observed lower expression levels of butyrate-sensing receptors in the hypothalamus of SHR, likely leading to the reduced effects of centrally administered butyrate on blood pressure in the SHR. Functional magnetic resonance imaging revealed reduced activation of cardioregulatory brain regions following central administration of butyrate in the SHR compared to control.

CONCLUSION

We demonstrated a reduced availability of serum butyrate in the SHR, possibly due to diminished colonic absorption. Reduced expression of butyrate-sensing receptors in the SHR hypothalamus may explain the reduced central responsiveness to butyrate, indicating microbial butyrate may play a role in blood pressure regulation.

Increased Abundance of Lactobacillales in the Colon of Beta-Adrenergic Receptor Knock Out Mouse Is Associated With Increased Gut Bacterial Production of Short Chain Fatty Acids and Reduced IL17 Expression in Circulating CD4+ Immune Cells

Emerging evidence suggests an associative link between gut dysbiosis, the autonomic nervous system (ANS) and the immune system in pathophysiology of neurogenic hypertension (HTN). However, the close interplay between these three systems presents us with difficulties in deciphering the cause-effect relationship in disease. The present study utilized beta 1 and 2 adrenergic receptor knock out (AdrB1^tm1BkkAdrB2^tm1Bkk/J KO) mice to isolate the effects of reduced overall sympathetic drive on gut microbiota and systemic immune system. We observed the following: (i) Diminished beta adrenergic signaling mainly reflects in shifts in the Firmicutes phyla, with a significant increase in abundance of largely beneficial Bacilli Lactobacillales in the KO mice; (ii) This was associated with increased colonic production of beneficial short chain fatty acids (SCFAs) butyrate, acetate and propionate, confirming functional microbiota shifts in the KO mice; (iii) Dampened systemic immune responses in the KO mice reflected in reduction on circulating CD4⁺.IL17⁺ T cells and increase in young neutrophils, both previously associated with shifts in the gut microbiota. Taken together, these observations demonstrate that reduced expression of beta adrenergic receptors may lead to beneficial shifts in the gut microbiota and dampened systemic immune responses. Considering the role of both in hypertension, this suggests that dietary intervention may be a viable option for manipulation of blood pressure via correcting gut dysbiosis.

Shifts in the Gut Microbiota Composition Due to Depleted Bone Marrow Beta Adrenergic Signaling Are Associated with Suppressed Inflammatory Transcriptional Networks in the Mouse Colon

The brain-gut axis plays a critical role in the regulation of different diseases, many of which are characterized by sympathetic dysregulation. However, a direct link between sympathetic dysregulation and gut dysbiosis remains to be illustrated. Bone marrow (BM)-derived immune cells continuously interact with the gut microbiota to maintain homeostasis in the host. Their function is largely dependent upon the sympathetic nervous system acting via adrenergic receptors present on the BM immune cells. In this study, we utilized a novel chimera mouse that lacks the expression of BM beta1/2 adrenergic receptors (b1/2-ARs) to investigate the role of the sympathetic drive to the BM in gut and microbiota homeostasis. Fecal analyses demonstrated a shift from a dominance of Firmicutes to Bacteroidetes phylum in the b1/2-ARs KO chimera, resulting in a reduction in Firmicutes/Bacteroidetes ratio. Meanwhile, a significant reduction in Proteobacteria phylum was determined. No changes in the abundance of acetate-, butyrate-, and lactate-producing bacteria, and colon pathology were observed in the b1/2-ARs KO chimera. Transcriptomic profiling in colon identified Killer Cell Lectin-Like Receptor Subfamily D, Member 1 (Klrd1), Membrane-Spanning 4-Domains Subfamily A Member 4A (Ms4a4b), and Casein Kinase 2 Alpha Prime Polypeptide (Csnk2a2) as main transcripts associated with the microbiota shifts in the b1/2-ARs KO chimera. Suppression of leukocyte-related transcriptome networks (i.e., function, differentiation, migration), classical compliment pathway, and networks associated with intestinal function, barrier integrity, and excretion was also observed in the colon of the KO chimera. Moreover, reduced expression of transcriptional networks related to intestinal diseases (i.e., ileitis, enteritis, inflammatory lesions, and stress) was noted. The observed suppressed transcriptome networks were associated with a reduction in NK cells, macrophages, and CD4⁺ T cells in the b1/2-ARs KO chimera colon. Thus, sympathetic regulation of BM-derived immune cells plays a significant role in modifying inflammatory networks in the colon and the gut microbiota composition. To our knowledge, this study is the first to suggest a key role of BM b1/2-ARs signaling in host-microbiota interactions, and reveals specific molecular mechanisms that may lead to generation of novel anti-inflammatory treatments for many immune and autonomic diseases as well as gut dysbiosis across the board.

Abstract P156: Fiber-rich Diet Suppresses Lactobacillus And Increases Blood Pressure In The Shr Independently Of T-lymphocyte Immune Responses

Introduction: Gut dysbiosis has been linked to hypertension in both rodents and humans. Microbial metabolites such as propionate have been shown to regulate blood pressure (BP), while butyrate, one of the major fermented end-products of fiber, reportedly produces beneficial anti-inflammatory effects in multiple dysbiosis-related diseases. Therefore, we tested the impact of a fiber-rich, butyrolytic diet on BP regulation and immune responses in the spontaneously hypertensive rats (SHR).

Methods: SHR (5 wo) were placed on either the fructooligosaccharides/inulin-rich diet (Fiber, N=6), or its calorie-matched control diet (Control, N=6) (Research Diets, Inc.) for 10 weeks. Baseline BP was measured by tail cuff every week for the duration of the study. Fecal samples were collected for HPLC analysis of butyrate, and Lactobacillus population by QPCR. Manganese-enhanced magnetic resonance imaging was used to monitor neural activity in cardioregulatory brain regions. Blood was analyzed for circulating lymphocyte populations previously implicated in BP control in the SHR (CD3 + CD45 + , CD4 + CD25 + , CD8 + ).

Results: Fiber-rich diet produced an increase in fecal butyrate levels as early as five weeks (Control vs. Fiber, 4.9umol/g vs. 9.7umol/g, p=0.068, N=6). This was associated with contraction of fecal Lactobacillus (47.5% vs. 5.9%, p=0.0008, N=6). However, we observed significantly higher systolic BP (181.4mmHg vs. 201.7 mmHg, p=0.0088, N=6) in the fiber group compared with control, beginning with week 9 post-diet switch. Changes in neural activation were observed in the paraventricular nucleus of hypothalamus (PVN) (3.3 voxel vs. 7.3 voxel, p=0.26) and amygdala (93.3 voxel vs. 31 voxel, p=0.0059, N=3). No changes in circulating T-lymphocytes were observed between the two groups: CD3 + CD45 + (32.4% vs. 32.1% lymphocytes); CD4 + CD25 + (1.05% vs. 0.78% lymphocytes); CD8 + (18.7% vs. 16.2% lymphocytes, N=6) at week 10 post-diet switch.

Conclusion: Fiber-rich diet suppression of Gut Lactobacillus is associated with increase in BP in the SHR, independently of T-lymphocyte responses. The observed higher neural activity in PVN and lower in amygdala in the fiber group suggest direct effects of gut bacterial metabolites on brain cardioregulatory regions.

Angiogenesis correlates with metastasis in melanoma

BACKGROUND

Angiogenesis has been correlated with melanoma progression, but its role in melanoma metastasis is unclear.

METHODS

To determine whether angiogenesis correlates with the presence of melanoma metastases, we compared the number of microvessels in the primary melanomas of 12 patients presenting with metastases to those of 13 patients without metastases. Patient groups were matched for gender, age, tumor depth, and histological type and anatomical location of the primary melanoma. Microvessels were stained with factor VIII antibody and counted.

RESULTS

Microvessel counts were significantly greater for the metastatic than the nonmetastatic melanomas (51.63+/-14.95 vs. 24.86+/-8.415; P < .0001). One hundred percent of the metastatic melanomas had a mean microvessel count of > or = 37, whereas only 8% of the nonmetastatic melanomas had a mean microvessel count of > or = 37 (sensitivity = 1.00, specificity = .92). Interestingly, patients with lymph node metastases had significantly lower microvessel counts than did patients with distant metastases (42.00+/-3.482 vs. 58.50+/-16.40; P < .05), and significantly higher microvessel counts than did patients without metastases (42.00+/-3.482 vs. 24.86+/-8.415; P < .001).

CONCLUSIONS

An increased number of microvessels in the primary tumors of patients with melanoma correlates with the simultaneous presence of metastases. This suggests that angiogenesis may be important in the process of melanoma metastasis.

Antigen retrieval in immunofluorescent testing of bullous pemphigoid

Direct immunofluorescence is an immunopathological technique frequently utilized for diagnosis of vesiculobullous disease such as bullous pemphigoid. Fresh-frozen tissue is required for immunofluorescent testing, making retrospective analysis difficult. In this study, we compared two methods of antigen retrieval in formalin-fixed, paraffin-embedded skin tissue from patients with bullous pemphigoid to determine if archival tissue, after use of an unmasking antigen, can be substituted for fresh-frozen tissue in the immunopathological study of skin. Paraffin-embedded tissue blocks from patients with bullous pemphigoid and patients with eosinophilic spongiotic dermatitis as the prodromal stage of bullous pemphigoid were obtained. Sections were mounted on poly-L-lysine-coated slides and the slides were deparaffinized. The methods of antigen retrieval included incubation with trypsin (0.1%) and microwave irradiation in urea (6 M). Antigen retrieval was followed by indirect immunofluorescence. Microwave irradiation was more effective in antigen retrieval than was incubation with trypsin (0.1%). Microwave irradiation in urea (6 M) produced more intense immunofluorescent staining than did trypsinization. Overall, positive basement membrane zone immunofluorescent staining was found in 60% of patients with a diagnosis of classical bullous pemphigoid and in 50% of patients with eosinophilic spongiotic dermatitis as the prodromal stage of bullous pemphigoid. Although the frozen-tissue method appeared more effective than the antigen-retrieval method in immunofluorescent testing of skin, the antigen-retrieval method can certainly be considered an option in retrospective studies. Antigen retrieval may be particularly advantageous in patients with eosinophilic spongiotic dermatitis in whom the diagnosis of bullous pemphigoid may not be suspected initially.

Crusted scabies in a patient with chronic graft-versus-host disease

We describe a 20-year-old man with chronic graft-versus-host disease and progressive cutaneous changes. His skin became more lichenified despite therapy with azathioprine, prednisone, and cyclosporine. Although it was initially thought that lichenoid graft-versus-host disease had developed, it was subsequently discovered that the patient had crusted (Norwegian) scabies.