Prophylactic antibiotic treatment exacerbates Graft vs. Host Disease-induced bone marrow failure and spleen hypoplasia

Acute graft vs. host disease (aGVHD) is a major complication following hematopoietic stem cell transplantation. Preclinical and clinical studies suggest aGVHD may be potentiated by gut damage and translocation of intestinal microbiota following toxic, pre-transplant conditioning protocols. We recently reported that aGVHD-induced bone marrow (BM) failure and splenic hypoplasia develops in the absence of gut damage suggesting that intestinal bacteria may not be required for disease pathogenesis.

Objective

Determine whether prophylactic gut decontamination with broad spectrum antibiotics (Abx) affects the onset and/or severity of aGVHD-induced BM and spleen damage.

Methods

Syngeneic (Bl6) or allogeneic (Balb/c) CD4+CD25−T cells (5×106 cells) were injected into NK cell-depleted Bl6 RAG1−/− recipients. Prior to T cell transfer, RAG1−/− mice received water (ab libitum) containing aspartame (Asp) or an Abx cocktail containing Asp, neomycin and vancomycin for 7 days prior to and following T-cell transfer.

Results

Treatment of allogeneic mice with Abx reduced colonic bacterial load by more than 20-fold when compared to their Asp-treated counterparts. Abx treatment also resulted in large and significant reductions in BM- and spleen-residing T cells and myeloid cells as well as circulating erythrocytes, platelets and hematocrit when compared to Asp treated mice. These Abx-induced alterations were associated with significant increases (~4-fold) in serum IL-6 levels compared to Asp-treated mice.

Conclusions

Prophylactic Abx treatment exacerbates aGVHD-induced BM failure and spleen hypoplasia.

CD4+ T Cells are both necessary and sufficient to induce acute graft vs. host disease in lymphopenic recipients

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially life-saving treatment for refractory/relapsing hematological malignancies, blood disorders or autoimmune diseases. However, approximately 40–50% of patients undergoing allogeneic HSCT will develop a multi-organ, inflammatory disorder called acute graft vs. host disease (aGVHD). Experimental and clinical studies suggest that intestinal injury due to toxic, pre-transplant conditioning protocols (e.g. lethal irradiation and/or chemotherapy) may play a major role in the development of aGVHD. However, recent studies from our laboratory as well as others, suggest that this may not be the case.

Objective

We wished to quantify and compare the onset and severity of aGVHD induced by the adoptive transfer of allogeneic T cells into untreated lymphopenic mice.

Methods

Four million allogeneic or syngeneic CD4+CD62L+CD25− T cells were transferred (i.p.) into NK cell-depleted RAG1−/− mice or RAG2−/−IL2rγ−/− double knock-out (DKO) mice and assessed daily for signs of aGVHD.

Results

We found that adoptive transfer of allogeneic but not syngeneic T cells into NK cell-depleted RAG1−/− or DKO mice induced many of the clinical and histological features of aGVHD including weight loss, inflammatory cytokine production and tissue inflammation. In addition, adoptive transfer of allogeneic T cells into each recipient induced severe anemia as well as dramatic reductions in bone marrow and spleen cellularity.

Conclusions

We conclude that naïve allogeneic CD4+T cells are both necessary and sufficient to induce aGVHD in lymphopenic recipients in the absence of toxic, pre-transfer conditioning.

T cell-mediated bone marrow and splenic hypoplasia in a mouse model of acute graft vs. host disease

A major limitation with use of hematopoietic stem cell transplantation to treat relapsing hematological malignancies is the development of a potentially lethal, multi-organ inflammatory disorder called acute graft versus host disease (aGVHD). Acute GVHD-associated bone marrow (BM) suppression and lymphoid tissue (LT) hypoplasia creates protracted immunodeficiency that greatly increases the risk of infections, bleeding and death.

Objective

We wished to define the role that allogeneic CD4+ T cells play in a mouse model of aGVHD-associated BM and LT aplasia that does not require lethal myeloablative conditioning.

Methods

Allogeneic CD4+CD25−T cells (0.5×106 cells) obtained from Bl6-H2-Ab1bm12 (Bl6-BM12) donor mice were adoptively transferred into sub-lethally irradiated C57Bl6 (Bl6) recipients. Mice were monitored daily for clinical signs of aGVHD.

Results

Adoptive transfer of allogeneic but not syngeneic T cells induced a time-dependent loss of survival and remarkable reductions of cellularity in the BM and spleen. Virtually all allogeneic mice developed severe anemia at 15 days post transfer. Flow cytometric analyses revealed dramatic and significant losses of CD4+ T cells, myeloid cells and NK cells in the BM and spleen indicating BM suppression and spleen hypoplasia. Interestingly, we observed little immune cell infiltration in the lungs, liver and skin of allogeneic recipients and no evidence of disease in any tissue of syngeneic mice. These data suggest that the major target tissues in this model of aGVHD are BM and spleen.

Conclusions

When taken together, these data demonstrate that adoptive transfer of allogeneic CD4+ T cells into sub-lethally irradiated recipients induces aGVHD-associated immunodeficiency.

JAK inhibition using tofacitinib for inflammatory bowel disease treatment: a hub for multiple inflammatory cytokines

The inflammatory diseases ulcerative colitis and Crohn's disease constitute the two main forms of inflammatory bowel disease (IBD). They are characterized by chronic, relapsing inflammation of the gastrointestinal tract, significantly impacting on patient quality of life and often requiring prolonged treatment. Existing therapies for IBD are not effective for all patients, and an unmet need exists for additional therapies to induce and maintain remission. Here we describe the mechanism of action of the Janus kinase (JAK) inhibitor, tofacitinib, for the treatment of IBD and the effect of JAK inhibition on the chronic cycle of inflammation that is characteristic of the disease. The pathogenesis of IBD involves a dysfunctional response from the innate and adaptive immune system, resulting in overexpression of multiple inflammatory cytokines, many of which signal through JAKs. Thus JAK inhibition allows multiple cytokine signaling pathways to be targeted and is expected to modulate the innate and adaptive immune response in IBD, thereby interrupting the cycle of inflammation. Tofacitinib is an oral, small molecule JAK inhibitor that is being investigated as a targeted immunomodulator for IBD. Clinical development of tofacitinib and other JAK inhibitors is ongoing, with the aspiration of providing new treatment options for IBD that have the potential to deliver prolonged efficacy and clinically meaningful patient benefits.

Extreme degree of ionization in homogenous micro-capillary plasma columns heated by ultrafast current pulses

Homogeneous plasma columns with ionization levels typical of megaampere discharges are created by rapidly heating gas-filled 520-μm-diameter channels with nanosecond rise time current pulses of 40 kA. Current densities of up to 0.3  GA cm^{-2} greatly increase Joule heating with respect to conventional capillary discharge Z pinches, reaching unprecedented degrees of ionization for a high-Z plasma column heated by a current pulse of remarkably low amplitude. Dense xenon plasmas are ionized to Xe^{28+}, while xenon impurities in hydrogen discharges reach Xe^{30+}. The unique characteristics of these hot, ∼300:1 length-to-diameter aspect ratio plasmas allow the observation of unexpected spectroscopic phenomena. Axial spectra show the unusual dominance of the intercombination line over the resonance line of He-like Al by nearly an order of magnitude, caused by differences in opacities in the axial and radial directions. These plasma columns could enable the development of sub-10-nm x-ray lasers.

Slamf1 controls monocyte / macrophage migration in experimental colitis. (117.5)

Signaling lymphocyte activation molecule (Slamf1) is a T cell co-stimulatory molecule and a regulator of cytokine production by macrophages and dendritic cells. Because Slamf1 positively regulates microbicidal mechanisms in macrophages, we evaluate whether Slamf1 would affect enterocolitis. To induce colitis, mouse CD45RBhi CD4+ T cells were transferred into RAG-/- or Slamf1-/- RAG-/- recipient mice. In a second set of experiments, an agonistic αCD40 antibody was administered to the same recipient strains to induce colitis. Whilst the absence of Slamf1 in RAG-/- recipients mitigated colitis, the function of disease-causing effector or regulatory T cells was not affected by the ablation of the receptor. Surprisingly, in Slamf1-/- mice monocyte / macrophage migration into the inflamed tissue was impaired not only in αCD40-induced colitis but also in two other in vivo models of inflammation: thioglycolate induced peritonitis and in an “air pouch” model in response to TNFα. Administering αSlamf1 to RAG-/- mice ameliorated enterocolitis and altered this migration. Slamf1 is a key contributor to the innate immune responses during experimental colitis by affecting the migration of monocytes / macrophages to the sites of inflammation. As αSlamf1 also mitigates the pathogenesis of colitis, SLAMF1 should be a plausible therapeutic target in treating inflammatory bowel diseases.

Differential gene expression and suppressive properties of ex vivo-generated vs. naturally-occurring regulatory T-cells (168.25)

We have recently reported a novel ex vivo method to convert large numbers of CD4+Foxp3- T-cells to induced regulatory T-cells (iTregs; CD4+Foxp3+) via their incubation with plate-bound CD3 mAb, IL-2, TGFβ and retinoic acid (RA) for 4 days. These iTregs possess enhanced immune-suppressive activity in vitro and in vivo when compared to naturally-occurring Tregs (nTregs; CD4+Foxp3+). The objectives of this study were to: a) quantify and compare mRNA transcripts for genes known to be associated with Treg function using flow-purified iTregs and nTregs obtained from Foxp3GFP reporter mice and b) evaluate the stability of iTreg-mediated suppression in vitro and in vivo. We found 8 genes associated with iTregs that were significantly up-regulated when compared with nTregs with CCL4 (132-fold), Granzyme A (18-fold) and Runx1 (14-fold) showing the most dramatic increases. We also observed significant downregulation of 19, Treg-associated genes with IL-18 (600-fold), CD7 (300-fold), and IL-7 (100-fold) showing the most dramatic reductions in iTregs vs. nTregs. In addition, we found that when ex vivo-generated iTregs were “rested” by culturing iTregs for an additional 3 days in the absence of CD3 mAb, TGFβ and RA but in the presence of IL-2, Foxp3 expression, proliferative activity and in vitro suppressive activity were maintained. Unexpectedly, we found that these cells were more potent than nTregs in reversing preexisting colitis in a mouse model of chronic gut inflammation.

Neither the Peyer’s patches, mesenteric lymph nodes, nor the spleen are required for induction of chronic colitis in mice (166.16)

The objective of this study was to evaluate the role of PPs, MLNs and spleen in the pathogenesis of chronic colitis induced in mice. For the first series of studies, we transferred sorted, naïve (CD4+CD45RBhigh) T-cells (5x105 cells) into sham-operated RAG-1-/- mice or into RAG-1-/- mice that had their MLNs, spleen or both tissues surgically removed. We found that at 8 wks following T-cell transfer, all four of the surgically-manipulated RAG-1-/- groups developed moderate-severe colitis that was not different among the four groups. Flow cytometric analysis revealed large and similar numbers of IFN-γ producing T-cells within the colonic lamina propria (LP) of all four groups. For the second series of studies we intercrossed lymphotoxinβ-deficient (LTβ-/-) mice with RAG-1-/- animals to generate LTβ-/-xRAG-/- offspring that were devoid of Peyer’s patches and most peripheral lymph nodes. Surprisingly, and in contrast to what has been reported for LTβ-/- mice, we found no evidence of MLNs in the LTβ-/-xRAG-/- mice suggesting that lymphocytes may be required for MLN development in LTβ-/- mice. Adoptive transfer of CD45RBhigh T-cells into splenectomized LTβ-/-xRAG-/- mice or their littermate controls (LTβ+/+x RAG-/-) induced rapid onset of colitis suggesting that neither the PPs, MLNs nor the spleen are required for induction of disease. The mechanisms by which naïve T-cells are converted to colitogenic effector cells in this model are currently under investigation.

LFA-1 (CD11a/CD18) is required for T-cell homing to the mesenteric lymph nodes and gut but not for T-cell activation during the induction of chronic colitis (112.19)

We have demonstrated that adoptive transfer of naïve LFA-1-deficient (CD11a-/-) T-cells into RAG-1-/- mice fails to induce chronic colitis whereas transfer of wild type T-cells induces chronic and unrelenting colonic inflammation. The objective of this study was to define the role that LFA-1 plays in T-cell activation and trafficking during the induction of chronic colitis in RAG-1-/- mice. In the first series of studies, we found that enteric antigen (EAg)-pulsed dendritic cells (DCs) induced a concentration-dependent increase in wild type (WT) and CD11a-/- CD4+ T-cell proliferation that was quantitatively very similar between the two groups whether we used bone marrow- or spleen-derived DCs, suggesting that LFA-1 is not critical for EAg-induced activation of T-cells in vitro. Short term trafficking studies (<24 hrs) revealed a major defect in the accumulation of CD11a-/- T-cells within the MLNs compared to WT T-cells. When the observation period was extended to 3 and 7 days post T-cell transfer, we observed approximately 2-3-fold more WT T-cells within the MLNs and colon than CD11a-/- T-cells however, cell analysis revealed similar losses of CFSE fluorescence in both the WT vs. CD11a-/- T-cells suggesting that both populations of T-cells proliferated to same extent in vivo. Taken together, our data suggest that LFA-1 is important for T-cell trafficking to the MLNs and colon but is not required for EAg-induced T-cell activation in vitro or in vivo.

Vascular biology and pathobiology of the liver: Report of a single-topic symposium

Portal hypertension and its complications account for the majority of morbidity and mortality that occurs in patients with cirrhosis. In addition to portal hypertension, a number of other vascular syndromes are also of great importance, especially the ischemia-reperfusion (IR) injury. With the identification of major vascular defects that could account for many of the clinical sequelae of these syndromes, the liver vasculature field has now integrated very closely with the broader vascular biology discipline. In that spirit, the Henry and Lillian Stratton Basic Research Single Topic Conference was held on the topic of Vascular Biology and Pathobiology of the Liver. The course took place approximately 10 years after the first American Association for the Study of Liver Disease (AASLD)-sponsored conference on this topic that occurred in Reston, Virginia. The conference initiated with an introduction to basic vascular cell signaling and then explored vascular biology specifically as it relates to liver cells. Subsequently, specific disease syndromes were discussed in more detail including portal hypertension and IR injury. Finally, clinical and translational sessions focused on emerging therapies and technologies to treat vascular diseases of the liver.

Nanoimaging with a compact extreme-ultraviolet laser

Images with a spatial resolution of 120-150 nm were obtained with 46.9 nm light from a compact capillary-discharge laser by use of the combination of a Sc-Si multilayer-coated Schwarzschild condenser and a free-standing imaging zone plate. The results are relevant to the development of compact extreme-ultraviolet laser-based imaging tools for nanoscience and nanotechnology.

Reflection mode imaging with nanoscale resolution using a compact extreme ultraviolet laser

We report the demonstration of reflection mode imaging of 100 nm-scale features using 46.9 nm light from a compact capillary-discharge laser. Our imaging system employs a Sc/Si multilayer coated Schwarzschild condenser and a freestanding zone plate objective. The reported results advance the development of practical and readily available surface and nanostructure imaging tools based on the use of compact sources of extreme ultraviolet light.

Demonstration of a desk-top size high repetition rate soft x-ray laser

We have demonstrated a new type of high repetition rate 46.9 nm capillary discharge laser that fits on top of a small desk and that it does not require a Marx generator for its excitation. The relatively low voltage required for its operation allows a reduction of nearly one order of magnitude in the size of the pulsed power unit relative to previous capillary discharge lasers. Laser pulses with an energy of ~ 13 microJ are generated at repetition rates up to 12 Hz. About (2-3) x 10 4 laser shots can be generated with a single capillary. This new type of portable laser is an easily accessible source of intense short wavelength laser light for applications.

Damage to extreme-ultraviolet Sc/Si multilayer mirrors exposed to intense 46.9-nm laser pulses

The damage threshold and damage mechanism of extreme-ultraviolet Sc/Si multilayer mirror coatings are investigated with focused nanosecond pulses at 46.9-nm radiation from a compact capillary-discharge laser. Damage threshold fluences of approximately 0.08 J/cm2 are measured for coatings deposited on both borosilicate glass and Si substrates. The use of scanning and transmission electron microscopy and small-angle x-ray diffraction techniques reveals the thermal nature of the damage mechanism. The results are relevant to the use of newly developed high-flux extreme-ultraviolet sources in applications.

Splenectomy attenuates streptococcal cell wall-induced arthritis and alters leukocyte activation

OBJECTIVE

To investigate the role of the spleen in the pathogenesis of streptococcal cell wall (SCW)-induced arthritis and determine the impact of splenectomy on monocytes and T cells involved in the arthritis.

METHODS

Female Lewis rats were separated into 4 groups: 1) saline-injected, sham-operated; 2) saline-injected, splenectomized; 3) peptidoglycan-polysaccharide (PG-PS)-injected, sham-operated; and 4) PG-PS-injected, splenectomized. After a 10-day recovery period, rats received a single intraperitoneal injection of saline or PG-PS (25 microg rhamnose/gm body weight). We evaluated the effect of splenectomy on joint inflammation, histopathology, leukocyte subtypes in blood and lymph nodes, cytokines, and cell surface expression of CD44 and CD45RC in the chronic phase of the disease (day 28).

RESULTS

Splenectomy dramatically decreased chronic joint inflammation and histopathologic damage as well as altered cell types in lymph nodes and peripheral blood, as analyzed by flow cytometry. Nitric oxide (NO) production, levels of interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor alpha, and a biomarker of Th1 cell predominance correlated with the level of joint inflammation. Surprisingly, in splenectomized animals, increased expression of adhesion molecules thought to track T cells to inflamed tissue were observed in lymph nodes.

CONCLUSION

The result of splenectomy was attenuation of SCW-induced arthritis and changes in mediators of inflammation, including T cell subsets, proinflammatory cytokines, and NO production. Splenectomy may remove an important antigen reservoir and alter immune cell activation in the SCW-induced arthritis model.

Therapeutic administration of nitric oxide synthase inhibitors reverses hyperalgesia but not inflammation in a rat model of polyarthritis

Nitric oxide (NO) has been postulated to play a role in pain as well as in inflammation. In the present studies, the effects of NO synthase (NOS) inhibitors on both pain and inflammation were examined in a rat model of polyarthritis. Female Lewis rats were injected intraperitoneally (i.p.) with peptidoglycan/polysaccharide (PG/PS) or saline to induce arthritis. Hind paw volume, response latency to thermal nociceptive stimulus and mechanical threshold were measured daily for the next 35 days. Paw inflammation, thermal hyperalgesia and mechanical allodynia developed in all rats that received PG/PS compared to saline. On day 19 (chronic inflammation phase), rats were given either N(G)-nitro-L-arginine methyl ester (L-NAME, non-selective NOS inhibitor, 100 mg/l), L-N (6)-(1-iminoethyl) lysine (L-NIL, selective inducible NOS inhibitor, 10 mg/l) or no drug in drinking water. By day 21, L-NAME treatment reversed the thermal hyperalgesia completely and this effect remained until day 35. Similarly, L-NIL treatment reversed thermal hyperalgesia from days 24 to 34. Neither treatment affected mechanical allodynia. Paw volume was not different between PG/PS treated and PG/PS plus L-NAME treated rats. However, the PG/PS plus L-NIL treatment produced an increase in paw volume greater than did PG/PS alone. Other rats were treated with PG/PS plus the antiinflammatory agent indomethacin (days 19-35). Indomethacin treatment reversed all the measured parameters, although the reversal of mechanical allodynia was only partial. These results suggest that NO is involved in thermal, but not mechanical sensory pathways and that the selective inhibition of inducible NOS activity exacerbates established inflammation.

Early albumin leakage in pulmonary endothelial monolayers exposed to varying levels of hyperoxia

We assessed the effect of varying levels of hyperoxia on 14C-albumin flux across bovine pulmonary artery endothelial cell (BPAEC) monolayers. Endothelialized nitrocellulose filters were mounted in Ussing-type chambers which were filled with cell culture medium (M 199). Equimolar amounts of 14C-labeled and unlabeled albumin were added to the "hot" and "cold" chambers, respectively, and the monolayers were exposed to 3 hours of varying levels of oxygen (16%, 30%, 40%, 60%, and 95%). When compared to 16% O2, exposure to hyperoxic gas mixtures of 40% or greater progressively increased albumin permeability across endothelial monolayers within 3 hours to a value 2.5 times higher at 95% O2 compared to 16% O2 (p < 0.001). Hyperoxia-induced permeability increases were prevented by catalase, superoxide dismutase, desferrioxamine, and allopurinol. Our data indicate that hyperoxia induces endothelial permeability changes more rapidly than previously reported even at O2 concentrations as low as 40%.

A diclofenac derivative without ulcerogenic properties

In this study, we assessed the effects of addition of a nitroxybutyl moiety to diclofenac on its ulcerogenic properties. The diclofenac derivative, 'nitrofenac', was examined in terms of its ability to induce acute gastric erosions and chronic-type gastric ulcers in rats and rabbits, respectively. The effects of these compounds on prostaglandin synthesis in the stomach and at a site of peripheral inflammation were also assessed, as were their anti-inflammatory properties in a model of acute inflammation. Diclofenac dose-dependently caused acute gastric mucosal injury in the rat at all doses tested (10-40 mg/kg), that was significantly greater in severity than that observed with the same doses of nitrofenac. In rabbits, twice-daily administration of diclofenac induced penetrating antral ulcers and small intestinal damage. No damage was observed in the stomach or small intestine of rabbits receiving nitrofenac. Diclofenac and nitrofenac exerted similar inhibitory effects on prostaglandin E2 synthesis in the stomach and in a carrageenan-sponge model of peripheral inflammation. These compounds exerted similar inhibitory effects on carrageenan-induced paw edema. Nitrofenac, but not diclofenac, caused a significant increase in plasma levels of nitrate/nitrite. These results suggest that the addition of a nitroxybutyl moiety to diclofenac markedly reduces the ulcerogenic properties of this compound without interfering with its ability to inhibit cyclo-oxygenase activity or to reduce acute inflammation.

Endotoxin induces bacterial translocation and increases xanthine oxidase activity

Previously, we documented that endotoxin induces bacterial translocation from the gut and that inhibition or inactivation of xanthine oxidase activity reduces endotoxin-induced bacterial translocation. Consequently, experiments were performed to correlate endotoxin-induced bacterial translocation with changes in intestinal mucosal structure and xanthine dehydrogenase and oxidase activity. Segments of the jejunum, ileum, cecum, proximal colon, distal colon, and liver were harvested from ICR mice 24 hr after IP administration of E. coli 0111:B4 endotoxin (0.1 mg). Xanthine dehydrogenase and oxidase activities were measured in these samples and correlated with intestinal morphology. Bacteria translocated from the intestines to extraintestinal organs in 70% of the mice receiving endotoxin, while the organs of control mice were sterile (p less than 0.01). Endotoxin injured primarily the ileal and cecal mucosa and increased ileal and hepatic xanthine dehydrogenase and cecal oxidase activities (p less than 0.05). These results suggest that xanthine oxidase-induced mucosal damage plays a role in endotoxin-induced bacterial translocation.