Attenuation of aortic graft arteriosclerosis by systemic administration of Allotrap peptide RDP58

Oral administration of RDP58 ameliorated DSS-induced colitis in intestinal microbiota dependent manner

BACKGROUND

Although the pathogenesis of inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), has not been fully elucidated, accumulating researches suggest that intestinal microbiota imbalance contributes to the development of IBD in patients and animal models. RDP58, a peptide-based computer-assisted rational design, has been demonstrated to be effective in protecting against a wide range of autoimmune and inflammatory diseases. However, the underlying mechanism by which RDP58 protects against IBD mediated by intestinal microbiota has yet to be elucidated.

METHODS

The colitis model was induced by continuously administering 2.5 % (wt/vol) dextran sodium sulfate (DSS) solution for 7 days. The manifestations of colon inflammation were assessed via daily weight changes, colon length, tumor necrosis factor-alpha (TNF-α) level, disease activity index (DAI) score, pathology score, and intestinal barrier permeability. Intestinal microbiota analysis was carried out by 16S-rRNA sequencing. Colonic short chain fatty acids (SCFAs) and regulatory T cells (Tregs) were also detected. To further confirm the protective effect of RDP58 on intestinal microbiota, broad-spectrum antibiotic cocktail (ABX) treatment and fecal microbial transplantation (FMT) experiment were performed.

RESULTS

Oral administration of RDP58 ameliorated DSS-induced mice colitis by altering the diversity and composition of intestinal microbiota. Notably, RDP58 significantly upregulated SCFAs-producing microbiota, thereby promoting the generation of Tregs. ABX and FMT were performed to verify the above mechanism.

CONCLUSIONS

RDP58 ameliorated DSS-induced colitis through altering intestinal microbiota and enhancing SCFAs and Tregs production in intestinal microbiota dependent manner, potentially provide a novel therapy for IBD.

Heme Oxygenases in Cardiovascular Health and Disease

Heme oxygenases are composed of two isozymes, Hmox1 and Hmox2, that catalyze the degradation of heme to carbon monoxide (CO), ferrous iron, and biliverdin, the latter of which is subsequently converted to bilirubin. While initially considered to be waste products, CO and biliverdin/bilirubin have been shown over the last 20 years to modulate key cellular processes, such as inflammation, cell proliferation, and apoptosis, as well as antioxidant defense. This shift in paradigm has led to the importance of heme oxygenases and their products in cell physiology now being well accepted. The identification of the two human cases thus far of heme oxygenase deficiency and the generation of mice deficient in Hmox1 or Hmox2 have reiterated a role for these enzymes in both normal cell function and disease pathogenesis, especially in the context of cardiovascular disease. This review covers the current knowledge on the function of both Hmox1 and Hmox2 at both a cellular and tissue level in the cardiovascular system. Initially, the roles of heme oxygenases in vascular health and the regulation of processes central to vascular diseases are outlined, followed by an evaluation of the role(s) of Hmox1 and Hmox2 in various diseases such as atherosclerosis, intimal hyperplasia, myocardial infarction, and angiogenesis. Finally, the therapeutic potential of heme oxygenases and their products are examined in a cardiovascular disease context, with a focus on how the knowledge we have gained on these enzymes may be capitalized in future clinical studies.

A central role of heme oxygenase-1 in cardiovascular protection

The intrinsic defense mechanisms of the body are critical in protecting tissues from injury in response to pathological stress. Heme oxygenase-1 (HO-1), a stress response protein, is induced in response to various pathological stimuli to serve a cytoprotective function. By degrading the oxidant heme and generating the antioxidant bilirubin and anti-inflammatory molecule carbon monoxide, HO-1 may protect cell from injury due to oxidative and pathological stress. Oxidative stress in the heart caused by ischemia and reperfusion leads to cardiomyocyte death and subsequent myocardial infarction. Vascular diseases including atherosclerosis, graft failure, and restenosis are all associated with reactive oxygen species-induced injury and inflammation. Given that cardiovascular disease is the leading cause of death worldwide, there is considerable interest in developing new strategies for preventing and treating cardiovascular disease. Since HO-1 is induced in the heart and blood vessels in response to various stresses, a role of HO-1 has been implicated in cardiovascular homeostasis. Numerous studies using pharmacological method or genetic approach have since demonstrated the cardiovascular protective function of HO-1. Importantly, a number of studies have associated human HO-1 gene promoter polymorphisms with risk for vascular diseases. Taken together, HO-1 has a great therapeutic potential for cardiovascular disease.

RDP58 does not prevent graft-versus-host disease after dog leukocyte antigen-nonidentical canine hematopoietic cell transplantation

Graft-versus-host disease (GVHD) remains a cause of substantial morbidity for patients undergoing allogeneic hematopoietic cell transplantation (HCT). The present study was undertaken to investigate the effectiveness of RDP58, a peptide derived from the human leukocyte antigen class I heavy chain, in preventing GVHD in the established dog leukocyte antigen (DLA)-nonidentical canine model. Dogs underwent HCT from unrelated DLA-nonidentical donors after conditioning with 920 cGy total body irradiation. Engraftment and achievement of full donor chimerism was seen in five of six dogs, whereas one dog showed rejection and died of marrow aplasia. All five dogs with engraftment developed acute GVHD and were euthanized at an average of 20.6 days after HCT. Compared with historical controls, the Suse of RDP58 neither prevented acute GVHD nor significantly prolonged survival of DLA-nonidentical HCT recipients.

Peptide-mediated immunosuppression

There is now a substantial body of data demonstrating the abilities of synthetic peptides and peptide analogues to inhibit the auto- and alloimmune response in vitro and in vivo. We have studied the immunomodulatory role of synthetic peptides derived from highly conserved regions of the class II MHC alpha chain. These MHC-derived peptides inhibit the rat, human, and mouse mixed lymphocyte response (MLR), proliferation to autoantigen, cytokine production, and cytolytic T lymphocyte (CTL) generation. Our studies demonstrated that the inhibitory effect of the MHC class II nonpolymorphic peptides is mediated through the induction of apoptosis in APCs via a nonclassic caspase-independent pathway. In addition, T lymphocytes initially stimulated in the presence of HLA-DQA1 are rendered hyporesponsive to subsequent stimuli. Immunomodulation by HLA-DQA1 was effective in vivo because it prevented both the priming and the effector function of primed allogeneic T cells in a murine DTH model. Our data demonstrate that peptides derived from highly conserved regions of the class II MHC alpha chain can alter T-lymphocyte immune responses both in vitro and in vivo. These results have important implications for the development of a novel therapy for immune mediated diseases.

Adipose Tissue, Inflammation, and Cardiovascular Disease

Mounting evidence highlights the role of adipose tissue in the development of a systemic inflammatory state that contributes to obesity-associated vasculopathy and cardiovascular risk. Circulating mediators of inflammation participate in the mechanisms of vascular insult and atheromatous change, and many of these inflammatory proteins are secreted directly from adipocytes and adipose tissue–derived macrophages. Several factors linking obesity with an increased cardiovascular risk have been identified. The adipocyte-specific secretory protein adiponectin is a particularly promising candidate in this context. Its levels are decreased in obesity. Adiponectin may mediate some of its demonstrated cardioprotective effects through its anti-inflammatory properties. In addition to decreased expression of beneficial adipokines, secretion of a host of inflammatory factors from visceral adipose tissue may contribute to the increased cardiovascular risk associated with obesity. The cardioprotective effects of many of the most popular drug regimens corroborate these conclusions, demonstrating that along with improvements in other therapeutic end points, they mediate improvements in systemic inflammation. In some cases, these improvements are attributable to direct suppression of inflammatory signaling in adipocytes. The targeted suppression of various proinflammatory cascades in adipocytes specifically represents an exciting new therapeutic opportunity for the cardiovascular disease area.

Heme oxygenase-1 (HO-1), a protective gene that prevents chronic graft dysfunction

Heme oxygenase-1 (HO-1) is a stress-responsive enzyme that acts during inflammatory reactions as the rate-limiting step in the catabolism of heme, yielding equimolar amounts of iron (Fe), biliverdin, and the gas carbon monoxide (CO). Expression of HO-1 regulates inflammatory and immune responses, such as those involved in the rejection of transplanted organs. We will discuss here accumulating evidence supporting the notion that expression of HO-1 in a transplanted organ can prevent its rejection. We will argue that the protective effects exerted by HO-1 are mediated to a large extent by the end products that it generates via the catabolism of heme. Better knowledge of how to enhance these protective effects is likely to help create new therapeutic strategies to improve the outcome of transplanted organs.