Hyperbaric oxygen therapy is well tolerated and effective for ulcerative colitis patients hospitalized for moderate-severe flares: a phase 2A pilot multi-center, randomized, double-blind, sham-controlled trial

BACKGROUND

Hyperbaric oxygen therapy (HBOT) markedly increases tissue oxygen delivery. Case series suggest it may have a potential therapeutic benefit in ulcerative colitis (UC). We investigated the therapeutic potential of HBOT as an adjunct to steroids for UC flares requiring hospitalization.

METHODS

The study was terminated early due to poor recruitment with 18 of the planned 70 patients enrolled. UC patients hospitalized for moderate-severe flares (Mayo score ≥6, endoscopic sub-score ≥2) were block randomized to steroids + daily HBOT (n = 10) or steroids + daily sham hyperbaric air (n = 8). Patients were blinded to study assignment, and assessments were performed by a blinded gastroenterologist. Primary outcome was the clinical remission rate at study day 5 (partial Mayo score ≤2 with no sub-score >1). Key secondary outcomes were: clinical response (reduction in partial Mayo score ≥2, rectal bleeding sub-score of 0-1) and progression to second-line therapy (colectomy or biologic therapy) during the hospitalization.

RESULTS

A significantly higher proportion of HBOT-treated patients achieved clinical remission at study day 5 and 10 (50 vs. 0%, p = 0.04). HBOT-treated patients less often required progression to second-line therapy during the hospitalization (10 vs. 63%, p = 0.04). The proportion requiring in-hospital colectomy specifically as second-line therapy for medically refractory UC was lower in the HBOT group compared to sham (0 vs. 38%, p = 0.07). There were no serious adverse events.

CONCLUSION

In this small, proof-of-concept, phase 2A trial, the use of HBOT as an adjunctive therapy to steroids for UC patients hospitalized for moderate-severe flares resulted in higher rates of clinical remission, and a reduction in rates of progression to second-line therapy during the hospitalization. Larger well-powered trials are needed, however, to provided definitive evidence of therapeutic benefit.

The microbiota regulates susceptibility to Fas-mediated acute hepatic injury

Whereas a significant role for intestinal microbiota in affecting the pathogenesis and progression of chronic hepatic diseases is well documented, the contribution of the intestinal flora to acute liver injury has not been extensively addressed. Elucidating the influence of the intestinal microbiota on acute liver inflammation would be important for better understanding the transition from acute injury to chronic liver disease. Using the Concanavalin A (ConA)-induced liver injury model in laboratory mice, we show that the severity of acute hepatic damage varies greatly among genetically identical mice raised in different environments and harboring distinct microbiota. Through reconstitution of germ-free (GF) mice, and the co-housing of conventional mice, we provide direct evidence that manipulation of the intestinal flora alters susceptibility to ConA-induced liver injury. Through deep sequencing of the fecal microbiome, we observe that the relative abundance of Ruminococcaceae, a Gram(+) family within the class Clostridia, but distinct from segmented filamentous bacteria, is positively associated with the degree of liver damage. Searching for the underlying mechanism(s) that regulate susceptibility to ConA, we provide evidence that the extent of liver injury following triggering of the death receptor Fas varies greatly as a function of the microbiota. We demonstrate that the extent of Fas-induced liver injury increases in GF mice after microbiota reconstitution, and decreases in conventionally raised mice following reduction in intestinal bacterial load, by antibiotic treatment. We also show that the regulation of sensitivity to Fas-induced liver injury is dependent upon the toll-like receptor signaling molecule MyD88. In conclusion, the status and composition of the intestinal microbiota determine the susceptibility to ConA-induced acute liver injury. The microbiota acts as a rheostat, actively modulating the extent of liver damage in response to Fas triggering.

Systematic review: The safety and efficacy of hyperbaric oxygen therapy for inflammatory bowel disease

BACKGROUND

Hyperbaric oxygen therapy (HBOT) provides 100% oxygen under pressure, which increases tissue oxygen levels, relieves hypoxia and alters inflammatory pathways. Although there is experience using HBOT in Crohn's disease and ulcerative colitis, the safety and overall efficacy of HBOT in inflammatory bowel disease (IBD) is unknown.

AIM

To quantify the safety and efficacy of HBOT for Crohn's disease (CD) and ulcerative colitis (UC). The rate of adverse events with HBOT for IBD was compared to the expected rate of adverse events with HBOT.

METHODS

MEDLINE, EMBASE, Cochrane Collaboration and Web of Knowledge were systematically searched using the PRISMA standards for systematic reviews. Seventeen studies involving 613 patients (286 CD, 327 UC) were included.

RESULTS

The overall response rate was 86% (85% CD, 88% UC). The overall response rate for perineal CD was 88% (18/40 complete healing, 17/40 partial healing). Of the 40 UC patients with endoscopic follow-up reported, the overall response rate to HBOT was 100%. During the 8924 treatments, there were a total of nine adverse events, six of which were serious. The rate of adverse events with HBOT in IBD is lower than that seen when utilising HBOT for other indications (P < 0.01). The risk of bias across studies was high.

CONCLUSIONS

Hyperbaric oxygen therapy is a relatively safe and potentially efficacious treatment option for IBD patients. To understand the true benefit of HBOT in IBD, well-controlled, blinded, randomised trials are needed for both Crohn's disease and ulcerative colitis.

Affinity of antigen encounter and other early B-cell signals determine B-cell fate

Three possible effector fates await the naïve follicular B cell following antigen stimulation in thymus-dependent reactions. Short-lived plasma cells produce an initial burst of germline-encoded protective antibodies, and long-lived plasma cells and memory B cells arise from the germinal center and function to enhance and sustain the humoral immune response. The inherent B-cell receptor affinity of naïve follicular B cells and the contribution of other early B-cell signals pre-determines the pattern of transcription factor expression and the differentiation path taken by these cells. High initial B-cell receptor affinity shunts naïve follicular B-cell clones towards the short-lived plasma cell fate, whereas modest-affinity clones are skewed towards a plasma cell fate and low-affinity clones are recruited into the germinal center and are selected for both long-lived plasma cells and memory B cell pathways. In the germinal center reaction, increased levels of the transcription factor interferon regulatory factor-4 drive the molecular program that dictates differentiation into the long-lived plasma cell phenotype but has no impact on the memory B cell compartment. We hypothesize that graded interferon regulatory factor-4 levels driven by signals to B cells, including B-cell receptor signal strength, are responsible for this branch point in the B-cell terminal differentiation pathway.

Mast cells are essential intermediaries in regulatory T-cell tolerance

Contrary to the proinflammatory role of mast cells in allergic disorders, the results obtained in this study establish that mast cells are essential in CD4+CD25+Foxp3+ regulatory T (T(Reg))-cell-dependent peripheral tolerance. Here we confirm that tolerant allografts, which are sustained owing to the immunosuppressive effects of T(Reg) cells, acquire a unique genetic signature dominated by the expression of mast-cell-gene products. We also show that mast cells are crucial for allograft tolerance, through the inability to induce tolerance in mast-cell-deficient mice. High levels of interleukin (IL)-9--a mast cell growth and activation factor--are produced by activated T(Reg) cells, and IL-9 production seems important in mast cell recruitment to, and activation in, tolerant tissue. Our data indicate that IL-9 represents the functional link through which activated T(Reg) cells recruit and activate mast cells to mediate regional immune suppression, because neutralization of IL-9 greatly accelerates allograft rejection in tolerant mice. Finally, immunohistochemical analysis clearly demonstrates the existence of this novel T(Reg)-IL-9-mast cell relationship within tolerant allografts.

The rise and fall of long-lived humoral immunity: terminal differentiation of plasma cells in health and disease

Long-lived humoral immune responses are a hallmark of thymus-dependent immunity. The cellular basis for enduring antibody-mediated immunity is long-lived memory B cells and plasma cells (PCs). Both of these cell populations acquire longevity as a result of antigen-specific, CD40-dependent, cognate interactions with helper T cells within germinal centers (GCs). At the molecular level, defined functional domains of CD40 control the post-GC fate of B cells. PC precursors that emerge from these GC reactions are highly proliferative and terminally differentiate to end-stage cells within the bone marrow (BM). The striking phenotypic similarities between the PC precursors and the putative malignant cell in multiple myeloma (MM) suggests that MM may result from the transformation of PC precursors. Within the domain of autoimmune disease, recent studies have shown that dysregulated migration of PCs to the BM may impact immune homeostasis and the development of lupus. Understanding the processes of normal PC differentiation will provide strategic insights into identifying therapeutic targets for the treatment of differentiated B-cell disorders.