A collaborative approach to improving representation in viral genomic surveillance

The lack of routine viral genomic surveillance delayed the initial detection of SARS-CoV-2, allowing the virus to spread unfettered at the outset of the U.S. epidemic. Over subsequent months, poor surveillance enabled variants to emerge unnoticed. Against this backdrop, long-standing social and racial inequities have contributed to a greater burden of cases and deaths among minority groups. To begin to address these problems, we developed a new variant surveillance model geared toward building 'next generation' genome sequencing capacity at universities in or near rural areas and engaging the participation of their local communities. The resulting genomic surveillance network has generated more than 1,000 SARS-CoV-2 genomes to date, including the first confirmed case in northeast Louisiana of Omicron, and the first and sixth confirmed cases in Georgia of the emergent BA.2.75 and BQ.1.1 variants, respectively. In agreement with other studies, significantly higher viral gene copy numbers were observed in Delta variant samples compared to those from Omicron BA.1 variant infections, and lower copy numbers were seen in asymptomatic infections relative to symptomatic ones. Collectively, the results and outcomes from our collaborative work demonstrate that establishing genomic surveillance capacity at smaller academic institutions in rural areas and fostering relationships between academic teams and local health clinics represent a robust pathway to improve pandemic readiness.

A collaborative approach to improve representation in viral genomic surveillance

The lack of routine viral genomic surveillance delayed the initial detection of SARS-CoV-2, allowing the virus to spread unfettered at the outset of the U.S. epidemic. Over subsequent months, poor surveillance enabled variants to emerge unnoticed. Against this backdrop, long-standing social and racial inequities have contributed to a greater burden of cases and deaths among minority groups. To begin to address these problems, we developed a new variant surveillance model geared toward building microbial genome sequencing capacity at universities in or near rural areas and engaging the participation of their local communities. The resulting genomic surveillance network has generated more than 1,000 SARS-CoV-2 genomes to date, including the first confirmed case in northeast Louisiana of Omicron, and the first and sixth confirmed cases in Georgia of the emergent BA.2.75 and BQ.1.1 variants, respectively. In agreement with other studies, significantly higher viral gene copy numbers were observed in Delta variant samples compared to those from Omicron BA.1 variant infections, and lower copy numbers were seen in asymptomatic infections relative to symptomatic ones. Collectively, the results and outcomes from our collaborative work demonstrate that establishing genomic surveillance capacity at smaller academic institutions in rural areas and fostering relationships between academic teams and local health clinics represent a robust pathway to improve pandemic readiness.

Author summary

Genomic surveillance involves decoding a pathogen’s genetic code to track its spread and evolution. During the pandemic, genomic surveillance programs around the world provided valuable data to scientists, doctors, and public health officials. Knowing the complete SARS-CoV-2 genome has helped detect the emergence of new variants, including ones that are more transmissible or cause more severe disease, and has supported the development of diagnostics, vaccines, and therapeutics. The impact of genomic surveillance on public health depends on representative sampling that accurately reflects the diversity and distribution of populations, as well as rapid turnaround time from sampling to data sharing. After a slow start, SARS-CoV-2 genomic surveillance in the United States grew exponentially. Despite this, many rural regions and ethnic minorities remain poorly represented, leaving significant gaps in the data that informs public health responses. To address this problem, we formed a network of universities and clinics in Louisiana, Georgia, and Mississippi with the goal of increasing SARS-CoV-2 sequencing volume, representation, and equity. Our results demonstrate the advantages of rapidly sequencing pathogens in the same communities where the cases occur and present a model that leverages existing academic and clinical infrastructure for a powerful decentralized genomic surveillance system.

Using glycyrrhizic acid to target sumoylation processes during Epstein-Barr virus latency

Cellular sumoylation processes are proposed targets for anti-viral and anti-cancer therapies. We reported that Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) dysregulates cellular sumoylation processes, contributing to its oncogenic potential in EBV-associated malignancies. Ginkgolic acid and anacardic acid, known inhibitors of sumoylation, inhibit LMP1-induced protein sumoylation; however, both drugs have adverse effects in hosts. Here we test the effects of glycyrrhizic acid, a medicinal botanical extract with anti-inflammatory, anti-carcinogenic, and anti-viral properties, on cellular sumoylation processes. While glycyrrhizic acid is known to inhibit EBV penetration, its affect on cellular sumoylation processes remains to be documented. We hypothesized that glycyrrhizic acid inhibits cellular sumoylation processes and may be a viable treatment for Epstein-Barr virus-associated malignancies. Results showed that glycyrrhizic acid inhibited sumoylation processes (without affecting ubiquitination processes), limited cell growth, and induced apoptosis in multiple cell lines. Similar to ginkgolic acid; glycyrrhizic acid targeted the first step of the sumoylation process and resulted in low levels of spontaneous EBV reactivation. Glycyrrhizic acid did not affect induced reactivation of the virus, but the presence of the extract did reduce the ability of the produced virus to infect additional cells. Therefore, we propose that glycyrrhizic acid may be a potential therapeutic drug to augment the treatment of EBV-associated lymphoid malignancies.

Potential mechanisms of cellular injury following exposure to a physiologically relevant species of inorganic mercury

Mercury is a toxic metal that is found ubiquitously in the environment. Humans are exposed to different forms of mercury via ingestion, inhalation, and/or dermal absorption. Following exposure, mercuric ions may gain access to target cells and subsequently lead to cellular intoxication. The mechanisms by which mercury accumulation leads to cellular injury and death are not understood fully. Therefore, purpose of this study was to identify the specific intracellular mechanisms that are altered by exposure to inorganic mercury (Hg²⁺). Normal rat kidney (NRK) cells were exposed to a physiologically relevant form of Hg²⁺, as a conjugate of cysteine (10 μM or 50 μM). Alterations in oxidative stress were estimated by measuring lipid peroxidation and mitochondrial oxidative stress. Alterations in actin and tubulin were measured using specific fluorescent dyes. Calcium levels were measured using Fluo-3 AM Calcium Indicator while autophagy was identified with Premo^™ Autophagy Sensor LC3B-GFP. The current findings show that exposure to Hg²⁺ leads to enhanced oxidative stress, alterations in cytoskeletal structure, increases in intracellular calcium, and enhanced autophagy. We have established a more complete understanding of intoxication and cellular injury induced by a relevant form of Hg²⁺ in proximal tubule cells.

Inhibition of hyaluronic acid formation sensitizes chronic myelogenous leukemia to treatment with doxorubicin

In the current study we examined the ability of 4-methylumbelliferone (4-MU), which can inhibit hyaluronic acid synthesis, to sensitize K562 chronic myelogenous leukemia (CML) cells to doxorubicin therapy. Exposure of K562 cells to doxorubicin led to increased hyaluronic acid synthase (HAS) gene expression and increased levels of cell surface hyaluronic acid. Furthermore, exposure of K562 cells to exogenous HA caused resistance to doxorubicin-induced cell death. The combination of low dose 4-MU and doxorubicin led to increased apoptosis when compared to higher doses of any agent alone. Additionally, treatment with 4-MU led to a significant reduction in doxorubicin-induced increase in HA cell surface expression. Mechanistically, 4-MU treatment led to an increase in p38 activation and PARP cleavage. The role of p38 in 4-MU/doxorubicin-treated K562 cells was confirmed when p38 inhibitors led to protection from 4-MU/doxorubicin-induced apoptosis. Together, results from this study suggest that treatment with 4-MU increases the sensitivity of CML to chemotherapeutics by decreasing their HA-mediated resistance to apoptosis.

Treatment with the hyaluronic Acid synthesis inhibitor 4-methylumbelliferone suppresses LPS-induced lung inflammation

Exposure to bacterial endotoxins, such as lipopolysaccharide (LPS), can lead to the induction of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). To date, there are no known effective treatments for LPS-induced inflammation. In the current study, we investigated the potential use of the hyaluronic acid (HA) synthesis inhibitor 4-methylumbelliferone (4-MU) on LPS-induced acute lung inflammation. Culturing LPS-activated immune cells with 4-MU led to reduced proliferation, reduced cytokine production, and an increase in apoptosis when compared to untreated cells. Treatment of mice with 4-MU led to protection from LPS-induced lung injury. Specifically, 4-MU treatment led to a reduction in LPS-induced hyaluronic acid synthase (HAS) messenger RNA (mRNA) levels, reduction in lung permeability, and reduction in proinflammatory cytokine production. Taken together, these results suggest that use of 4-MU to target HA production may be an effective treatment for the inflammatory response following exposure to LPS.

Attenuation of myocardial fibrosis with curcumin is mediated by modulating expression of angiotensin II AT1/AT2 receptors and ACE2 in rats

Curcumin is known to improve cardiac function by balancing degradation and synthesis of collagens after myocardial infarction. This study tested the hypothesis that inhibition of myocardial fibrosis by curcumin is associated with modulating expression of angiotensin II (Ang II) receptors and angiotensin-converting enzyme 2 (ACE2). Male Sprague Dawley rats were subjected to Ang II infusion (500 ng/kg/min) using osmotic minipumps for 2 and 4 weeks, respectively, and curcumin (150 mg/kg/day) was fed by gastric gavage during Ang II infusion. Compared to the animals with Ang II infusion, curcumin significantly decreased the mean arterial blood pressure during the course of the observation. The protein level of the Ang II type 1 (AT1) receptor was reduced, and the Ang II type 2 (AT2) receptor was up-regulated, evidenced by an increased ratio of the AT2 receptor over the AT1 receptor in the curcumin group (1.2±0.02%) vs in the Ang II group (0.7±0.03%, P<0.05). These changes were coincident with less locally expressed AT1 receptor and enhanced AT2 receptor in the intracardiac vessels and intermyocardium. Along with these modulations, curcumin significantly decreased the populations of macrophages and alpha smooth muscle actin-expressing myofibroblasts, which were accompanied by reduced expression of transforming growth factor beta 1 and phosphorylated-Smad2/3. Collagen I synthesis was inhibited, and tissue fibrosis was attenuated, as demonstrated by less extensive collagen-rich fibrosis. Furthermore, curcumin increased protein level of ACE2 and enhanced its expression in the intermyocardium relative to the Ang II group. These results suggest that curcumin could be considered as an add-on therapeutic agent in the treatment of fibrosis-derived heart failure patient who is intolerant of ACE inhibitor therapy.

Treatment with the hyaluronic acid synthesis inhibitor 4-methylumbelliferone suppresses SEB-induced lung inflammation

Exposure to bacterial superantigens, such as staphylococcal enterotoxin B (SEB), can lead to the induction of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). To date, there are no known effective treatments for SEB-induced inflammation. In the current study we investigated the potential use of the hyaluronic acid synthase inhibitor 4-methylumbelliferone (4-MU) on staphylococcal enterotoxin B (SEB) induced acute lung inflammation. Culturing SEB-activated immune cells with 4-MU led to reduced proliferation, reduced cytokine production as well as an increase in apoptosis when compared to untreated cells. Treatment of mice with 4-MU led to protection from SEB-induced lung injury. Specifically, 4-MU treatment led to a reduction in SEB-induced HA levels, reduction in lung permeability, and reduced pro-inflammatory cytokine production. Taken together, these results suggest that use of 4-MU to target hyaluronic acid production may be an effective treatment for the inflammatory response following exposure to SEB.

Development of a novel treatment for leukemia directed at tumor-associated mRNA splicing

This report describes a novel approach to cancer therapy that targets genes that are preferentially alternatively spliced and expressed in leukemia. We developed CD44v6 and CD44v8 splicing constructs fused with GFP or a humanized fragment of Pseudomonas aeruginosa exotoxin A (hPE24). Transfection of K562 leukemia cells with the GFP-linked splicing constructs led to subsequent production of detectable levels of GFP. Transfection of K562 cells with the hPE24-linked splicing constructs led to significant reduction of cell viability and an increase in the induction of apoptosis. Normal human PBMCs were unaffected by following transfection with these constructs.

The role of hyaluronic acid in SEB-induced acute lung inflammation

We investigated the role of the extracellular matrix component, hyaluronic acid (HA) in SEB-induced ALI/ARDS. Intranasal exposure of mice to SEB led to a significant increase in the level of soluble hyaluronic acid in the lungs. Similarly, in an endothelial cell/spleen cell co-culture, SEB exposure led to significant increases in soluble levels of hyaluronic acid, cellular proliferation, and cytokine production compared with SEB-exposed spleen cells or endothelial cells alone. Exposure of SEB-activated spleen cells to hyaluronic acid led to increased cellular proliferation and increased cytokine production. SEB-induced cytokine production and proliferation in vitro were significantly reduced by the hyaluronic acid blocking peptide, Pep-1. Finally, treatment of SEB-exposed mice with Pep-1 significantly reduced SEB-induced ALI/ARDS, through reduction of cytokine production and numbers of lung inflammatory cells, compared to mice treated with a control peptide. Together, these results suggest the possibility of targeting HA for the treatment of SEB-induced ALI/ARDS.

Role of CD44 in lymphokine-activated killer cell-mediated killing of melanoma

In the current study, we examined the potential significance of CD44 expression on lymphokine-activated killer (LAK) cells in their interaction and killing of melanoma cells. Stimulation of splenocytes with IL-2 led to a significant increase in the expression of CD44 on T cells, NK cells, and NKT cells. Treatment of melanoma-bearing CD44 WT mice with IL-2 led to a significant reduction in the local tumor growth while treatment of melanoma-bearing CD44 KO mice with IL-2 was ineffective at controlling tumor growth. Furthermore, the ability of splenocytes from IL-2-treated CD44 KO mice to kill melanoma tumor targets was significantly reduced when compared to the anti-tumor activity of splenocytes from IL-2-treated CD44 WT mice. The importance of CD44 expression on the LAK cells was further confirmed by the observation that adoptively transferred CD44 WT LAK cells were significantly more effective than CD44 KO LAK cells at controlling tumor growth in vivo. Next, the significance of the increased expression of CD44 in tumor killing was examined and showed that following stimulation with IL-2, distinct populations of cells with low (CD44(lo)) or elevated (CD44(hi)) expression of CD44 are generated and that the CD44(hi) cells are responsible for killing of the melanoma cells. The reduced killing activity of the CD44 KO LAK cells did not result from reduced activation or expression of effector molecules but was due, at least in part, to a reduced ability to adhere to B16F10 tumor cells.

Plumbagin treatment leads to apoptosis in human K562 leukemia cells through increased ROS and elevated TRAIL receptor expression

This study examined the ability of plumbagin to induce apoptosis in chronic myelogenous leukemia (CML). Plumbagin exposure led to a significant reduction in cell viability and the induction of apoptosis. Mechanistically, plumbagin treatment led to elevated levels of ROS. Plumbagin-induced apoptosis was inhibited by N-acetyl L-cysteine (NAC) and PEG-catalase. Furthermore, plumbagin exposure led to elevated expression of DR4 and DR5 and increased killing through soluble TRAIL. The plumbagin-induced increase in DR4 and DR5 was inhibited by treatment with NAC. Together, this study suggests that plumbagin may be an effective treatment of CML through increased sensitivity to TRAIL-mediated killing.

Role of CD4+CD25+ T regulatory cells in IL-2-induced vascular leak

T regulatory cells (CD4(+)CD25(+)) play an important role in the regulation of the immune response. However, little is known about the ability of T regulatory cells to regulate endothelial cell (EC) damage following activation of lymphocytes with IL-2. Therefore, in the current study, we examined the role of T regulatory cells and the subsequent T(h)1/T(h)2 bias in IL-2-mediated EC injury using the well-characterized C57BL/6 (T(h)1-biased) and BALB/c (T(h)2-biased) models. Following IL-2 treatment, BALB/c mice were less susceptible to IL-2-induced vascular leak syndrome (VLS) compared with C57BL/6 mice. Splenocytes from BALB/c mice displayed less cytotoxicity against ECs compared with those from C57BL/6 mice. Interestingly, BALB/c mice had significantly higher numbers of CD4(+)CD25(+) T regulatory cells, which proliferated more profoundly following IL-2 treatment, compared with CD4(+)CD25(+) T regulatory cells from C57BL/6 mice. In addition, T regulatory cells from naive BALB/c mice were more potent suppressors of anti-CD3 mAb-stimulated proliferation of T cells than similar cells from C57BL/6 mice. Depletion of T regulatory cells in both BALB/c and C57BL/6 mice led to a significant increase in IL-2-induced VLS. Together, the results from this study suggest that CD4(+)CD25(+) T regulatory cells play an important role in the regulation of IL-2-induced EC injury.

Cannabidiol-Induced Apoptosis in Human Leukemia Cells: A Novel Role of Cannabidiol in the Regulation of p22phox and Nox4 Expression

In the current study, we examined the effects of the nonpsychoactive cannabinoid, cannabidiol, on the induction of apoptosis in leukemia cells. Exposure of leukemia cells to cannabidiol led to cannabinoid receptor 2 (CB2)-mediated reduction in cell viability and induction in apoptosis. Furthermore, cannabidiol treatment led to a significant decrease in tumor burden and an increase in apoptotic tumors in vivo. From a mechanistic standpoint, cannabidiol exposure resulted in activation of caspase-8, caspase-9, and caspase-3, cleavage of poly(ADP-ribose) polymerase, and a decrease in full-length Bid, suggesting possible cross-talk between the intrinsic and extrinsic apoptotic pathways. The role of the mitochondria was further suggested as exposure to cannabidiol led to loss of mitochondrial membrane potential and release of cytochrome c. It is noteworthy that cannabidiol exposure led to an increase in reactive oxygen species (ROS) production as well as an increase in the expression of the NAD(P)H oxidases Nox4 and p22(phox). Furthermore, cannabidiol-induced apoptosis and reactive oxygen species (ROS) levels could be blocked by treatment with the ROS scavengers or the NAD(P)H oxidase inhibitors. Finally, cannabidiol exposure led to a decrease in the levels of p-p38 mitogen-activated protein kinase, which could be blocked by treatment with a CB2-selective antagonist or ROS scavenger. Together, the results from this study reveal that cannabidiol, acting through CB2 and regulation of Nox4 and p22(phox) expression, may be a novel and highly selective treatment for leukemia.

Mouse B cell activation is inhibited by CD44 cross-linking

Lymphocyte activation and trafficking are indispensable to the immune system. CD44 is an adhesion molecule with known importance in T cell activation, lymphocyte trafficking, and tumor metastasis. Although CD44 has been shown to participate in the activation, rolling and adhesion, and homing of T cells, the role of CD44 on B cells is relatively unknown. The effects of CD44 cross-linking on murine B cell activation via CD40L was explored using the anti-CD44 mAbs RK3G9 and IM7. When immobilized on a plate, both RK3G9 and IM7 were found to strongly inhibit B cell proliferation and Ig production, especially at lower cell input concentrations. IgE inhibition was especially prominent. In contrast, soluble RK3G9 added to the B cell cultures had no effect. The inhibitory effect of anti-CD44 on B cell activation was not influenced by the addition of the anti-FcgammaRII, indicating that Fc cross-linking did not play a role in this inhibition. As Ig production requires several days for both B cell proliferation and differentiation to occur, the effects of delayed addition of immobilized anti-CD44 mAbs were studied, and the results indicated no inhibition after 96 hrs of culture. Finally, B cells were activated by either LPS or anti-IgM F(ab')2. While LPS-induced B cell activation was inhibited by immobilized anti-CD44 mAbs, anti-IgM activation was refractory. Interestingly, addition of both anti-IgM and CD40L or LPS resulted in some modulation of the inhibitory activity. These results suggest that CD44 cross-linking could control polyclonal B cell activation by CD40L, but allow sIgM/CD40L activation to continue.

Δ-9-Tetrahydrocannabinol Enhances Breast Cancer Growth and Metastasis by Suppression of the Antitumor Immune Response

In the current study, we tested the central hypothesis that exposure to Delta-9-tetrahydrocannabinol (Delta9-THC), the major psychoactive component in marijuana, can lead to enhanced growth of tumors that express low to undetectable levels of cannabinoid receptors by specifically suppressing the antitumor immune response. We demonstrated that the human breast cancer cell lines MCF-7 and MDA-MB-231 and the mouse mammary carcinoma 4T1 express low to undetectable levels of cannabinoid receptors, CB1 and CB2, and that these cells are resistant to Delta9-THC-induced cytotoxicity. Furthermore, exposure of mice to Delta9-THC led to significantly elevated 4T1 tumor growth and metastasis due to inhibition of the specific antitumor immune response in vivo. The suppression of the antitumor immune response was mediated primarily through CB2 as opposed to CB1. Furthermore, exposure to Delta9-THC led to increased production of IL-4 and IL-10, suggesting that Delta9-THC exposure may specifically suppress the cell-mediated Th1 response by enhancing Th2-associated cytokines. This possibility was further supported by microarray data demonstrating the up-regulation of a number of Th2-related genes and the down-regulation of a number of Th1-related genes following exposure to Delta9-THC. Finally, injection of anti-IL-4 and anti-IL-10 mAbs led to a partial reversal of the Delta9-THC-induced suppression of the immune response to 4T1. Such findings suggest that marijuana exposure either recreationally or medicinally may increase the susceptibility to and/or incidence of breast cancer as well as other cancers that do not express cannabinoid receptors and are resistant to Delta9-THC-induced apoptosis.

Role of CD44 and its v7 isoform in staphylococcal enterotoxin B-induced toxic shock: CD44 deficiency on hepatic mononuclear cells leads to reduced activation-induced apoptosis that results in increased liver damage

Exposure to bacterial superantigens such as staphylococcal enterotoxin B (SEB) leads to the induction of toxic shock syndrome which results in multiorgan failure, including liver damage. In the present study, we investigated the role of CD44 in SEB-induced liver injury. Injection of SEB into d-galactosamine-sensitized CD44 wild-type (WT) mice led to a significant increase in CD44 expression on liver T cells, NK cells, and NKT cells. Administration of SEB to CD44 knockout (KO) mice caused significantly enhanced liver damage which correlated with elevated numbers of T cells, NK cells, NKT cells, and macrophages in the liver and increased production of tumor necrosis factor alpha and gamma interferon compared to CD44 WT mice. Furthermore, liver mononuclear cells from CD44 KO mice were resistant to SEB-induced apoptosis, and cDNA microarray analysis revealed that SEB activation of such cells led to the induction of several antiapoptotic genes and repression of proapoptotic genes. Examination of CD44 isoforms revealed that SEB exposure altered CD44 variant 7 (v7) isoform expression. Interestingly, mice bearing a specific deletion of the CD44v7 exon exhibited increased susceptibility to SEB-induced hepatitis. Finally, treatment of CD44 WT mice with anti-CD44 monoclonal antibodies reduced expression of CD44 in liver mononuclear cells and caused increased susceptibility to SEB-induced liver injury. Together, these data demonstrate that the expression of CD44 and/or CD44v7 on SEB-activated liver mononuclear cells facilitates their rapid apoptosis, thereby preventing severe liver injury in wild-type mice, and suggest that CD44 plays an important role in the regulation and elimination of immune cells in the liver.

Activation through Cannabinoid Receptors 1 and 2 on Dendritic Cells Triggers NF-κB-Dependent Apoptosis: Novel Role for Endogenous and Exogenous Cannabinoids in Immunoregulation

The precise role of cannabinoid receptors (CB)1 and CB2, as well as endogenous ligands for these receptors, on immune cells remains unclear. In the current study, we examined the effect of endogenous and exogenous cannabinoids on murine bone marrow-derived dendritic cells (DCs). Addition of Delta(9)-tetrahydrocannabinol (THC), a major psychoactive component found in marijuana or anandamide, an endogenous cannabinoid, to DC cultures induced apoptosis in DCs. DCs expressed CB1 and CB2 receptors and the engagement of both receptors was necessary to trigger apoptosis. Treatment with THC induced caspase-2, -8, and -9 activation, cleavage of Bid, decreased mitochondrial membrane potential, and cytochrome c release, suggesting involvement of death-receptor and mitochondrial pathways. DCs from Bid-knockout mice were sensitive to THC-induced apoptosis thereby suggesting that Bid was dispensable. There was no induction of p44/p42 MAPK, p38 MAPK, or stress-activated protein/JNK pathway in THC-treated DCs. However, THC treatment induced phosphorylation of IkappaB-alpha, and enhanced the transcription of several apoptotic genes regulated by NF-kappaB. Moreover, inhibition of NF-kappaB was able to block THC-induced apoptosis in DCs. Lastly, in vivo treatment of mice with THC caused depletion of splenic DCs. Together, our study demonstrates for the first time that endogenous and exogenous cannabinoids may suppress the immune response through their ability to induce apoptosis in DCs.

Fas Ligand-dependent and -independent mechanisms of toxicity induced by T cell lymphomas in lymphoid organs and in the liver

In the current study, we investigated the effect of growth of FasL(+) tumors in vivo on the functions of peripheral lymphoid organs and the liver. Injection of FasL(+) LSA tumor cells into syngeneic C57BL/6 wild-type mice but not C57BL/6 lpr/lpr (Fas-deficient) mice caused apoptosis in splenocytes. Spleen cells expressing CD3, CD4, CD8, CD19, Mac-3, and CD44 were all susceptible to tumor-induced apoptosis. Also, activated T cells were more sensitive to apoptosis induced by LSA tumor cell lysate when compared to naïve T cells. In contrast, anti-Fas Abs (Jo2) induced apoptosis in only activated but not naïve T cells. When the LSA tumor-bearing mice were injected with a superantigen (SEA), these mice showed a significant decrease in the expansion of SEA-reactive Vbeta3(+) and Vbeta11(+) T cells. When injected into syngeneic mice, the FasL(+) LSA tumor cells caused hepatotoxicity, as indicated by an increase in serum aspartate aminotransferase (AST) levels. Interestingly, Fas-deficient C57BL/6 lpr/lpr mice also showed significant AST levels in the serum following LSA tumor growth. Moreover, hepatocytes isolated from C57BL/6 wild-type and C57BL/6 lpr/lpr mice were equally susceptible to apoptosis induced by LSA tumor cell lysate in vitro. Using cDNA array, LSA tumor cells were found to express several cytokine genes including IL-2, IL-7, IL-11, IL-13, IL-16, lymphotoxin beta, and tumor necrosis factor beta. Together, these data suggested that, in mice bearing FasL(+) LSA tumor, the immunotoxicity is FasL-based, whereas the hepatotoxicity, at least in part, may be FasL-independent.

Combined deficiency in CD44 and Fas leads to exacerbation of lymphoproliferative and autoimmune disease

Patients with mutations in Fas develop autoimmune lymphoproliferative disease (ALPS), while their family members with similar mutations are often normal, thereby suggesting that additional factors may play a role in the development of ALPS. In the current study, we tested the role of CD44 in the development of lymphoproliferative disease by generating CD44(-/-)/Fas(-/-) mice, which failed to express CD44 and Fas, and compared them to CD44(+/+)/Fas(-/-) mice that expressed CD44, but not Fas. The results showed that CD44(-/-)/Fas(-/-) mice developed a more severe lymphoproliferative and autoimmune disease when compared to CD44(+/+)/Fas(-/-) mice. This was indicated by increased numbers of cells in their lymph nodes, and a greater proportion of B220(+)CD4(-)CD8(-) (double-negative) T cells as well as antibodies against single-stranded DNA and chromatin. The heightened severity of lymphoproliferative disease seen in CD44(-/-)/Fas(-/-) mice correlated with increased resistance of T cells, but not B cells, to undergo activation-induced cell death (AICD). The current study suggests that deficiency in CD44 in combination with a defect in one of the molecules involved in the death receptor family such as Fas can further down-regulate AICD, and exacerbate the lymphoproliferative and autoimmune disease.

Targeted deletion of CD44v7 exon leads to decreased endothelial cell injury but not tumor cell killing mediated by interleukin-2-activated cytolytic lymphocytes

In the current study, we investigated the nature and role of CD44 variant isoforms involved in endothelial cell (EC) injury and tumor cell cytotoxicity mediated by IL-2-activated killer (LAK) cells. Treatment of CD44 wild-type lymphocytes with IL-2 led to increased gene expression of CD44 v6 and v7 variant isoforms and to significant induction of vascular leak syndrome (VLS). CD44v6-v7 knockout (KO) and CD44v7 KO mice showed markedly reduced levels of IL-2-induced VLS. The decreased VLS in CD44v6-v7 KO and CD44v7 KO mice did not result from differential activation and expansion of CD8+ T cells, NK, and NK-T cells or from altered degree of perivascular lymphocytic infiltration in the lungs. LAK cells from CD44v7 KO mice showed a significant decrease in their ability to adhere to and mediate lysis of EC but not lysis of P815 tumor cells in vitro. CD44v7-mediated lysis of EC by LAK cells was dependent on the activity of phosphatidylinositol 3-kinase and tyrosine kinases. Interestingly, IL-2-activated LAK cells expressing CD44hi but not CD44lo were responsible for EC lysis. Furthermore, lysis of EC targets could be blocked by addition of soluble or enzymatic cleavage of CD44v6-v7-binding glycosaminoglycans. Finally, anti-CD44v7 mAbs caused a significant reduction in the adherence to and killing of EC and led to suppression of IL-2-induced VLS. Together, this study suggests that the expression of CD44v7 on LAK cells plays a specific role in EC injury and that it may be possible to reduce EC injury but not tumor cell killing by specifically targeting CD44v7.

Regulation of interleukin-2-induced vascular leak syndrome by targeting CD44 using hyaluronic acid and anti-CD44 antibodies

Previous studies from our laboratory demonstrated that CD44 knockout mice exhibit marked decrease in interleukin (IL)-2-induced vascular leak syndrome (VLS), thereby suggesting a role for CD44 in VLS. In the current study, we tested whether treatment with mAbs against CD44 or hyaluronic acid (HA), the ligand for CD44, can abrogate IL-2-induced VLS. Interestingly, administration of HA caused a marked increase in IL-2-induced VLS in the lungs and liver of C57BL/6 mice. In contrast, use of anti-CD44 mAbs reduced IL-2-induced VLS in the lungs and liver. Treatment with HA enhanced the IL-2-induced edema and lymphocytic infiltration in these organs and caused marked increase in IL-2-induced lymphokine-activated killer (LAK) cell activity, whereas administration of anti-CD44 mAbs caused a significant decrease in edema and LAK activity but similar levels of lymphocytic infiltration. Anti-CD44 mAbs, but not HA caused marked downregulation of CD44 expression on LAK cells. These studies demonstrate that molecular targeting of CD44 may serve as a useful tool to selectively alter the LAK activity and to prevent endothelial cell injury induced by IL-2.

Analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced gene expression profile in vivo using pathway-specific cDNA arrays

In the current study, we used pathway-specific cDNA arrays to detect the transcriptional signature induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in vivo by studying simultaneously the expression profiles of 83 genes involved in apoptosis, cytokine production and angiogenesis. To this end, C57BL/6 mice were injected i.p. with 50 microg/kg body weight of TCDD and 1 or 3 days later, the thymus was analyzed for gene expression profiles. In the thymus, 23 out of 37 apoptotic genes screened were up-regulated by TCDD by a factor of two or more when compared to the vehicle-treated controls. In contrast, in the spleen, 20 out of 22 and in the liver, 16 out of 37 apoptotic genes were up-regulated. In the thymus, several genes encoding caspases, and members of the TNF family, including Fas ligand, were induced. Also, in the thymus, eight out of 23, and in the spleen, six out of 23 cytokine genes were up-regulated. In the liver and to a lesser extent in the thymus, certain angiogenesis genes were induced while others were repressed. When mice were injected with 0.1, 1, 10 or 50 microg/kg body weight of TCDD and the thymus was analyzed for apoptotic genes 1 day later, a dose-dependent response was not seen with most apoptotic genes. However, certain apoptotic genes were induced in the thymus even at low doses of 0.1 microg/kg body weight of TCDD. These data demonstrate that TCDD alters the expression of a large array of genes involved in apoptosis, cytokine production and angiogenesis. Thus, pathway-specific cDNA arrays may help in the identification of specific gene expression profiles induced by xenobiotics and to delineate the molecular mechanisms of toxicity.

Role of CD44 in activation-induced cell death: CD44-deficient mice exhibit enhanced T cell response to conventional and superantigens

T cells upon activation are known to up-regulate CD44 expression. However, the precise function of CD44 on activated T cells is not clear. In this report, we demonstrate that signaling through CD44 plays an important role in activation-induced cell death (AICD). CD44 knockout (KO) mice had an elevated in vivo primary and in vitro secondary response to challenge with conalbumin, anti-CD3 mAb and staphylococcal enterotoxin A (SEA), which correlated with reduced AICD when compared to CD44 wild-type mice. In addition, CD44 KO mice exhibited increased delayed-type hypersensitivity response to dinitrofluorobenzene. In a model examining in vitro AICD, splenocytes from CD44 KO mice showed resistance to TCR-mediated apoptosis when compared to splenocytes from CD44 wild-type mice. In addition, signaling through CD44 led to increased apoptosis in TCR-activated but not resting T cells from CD44 wild-type mice without affecting Fas expression. Injection of SEA into mice deficient in CD44 and Fas (CD44 KO/lpr) led to an increased primary response when compared to mice that expressed CD44 but not Fas (CD44 WT/lpr), suggesting that the enhanced response to SEA was dependent on CD44 but not Fas expression. Administration of anti-CD44 mAb into CD44 wild-type mice caused a significant decrease in antigen-specific T cell response. Together, these data implicate CD44 as an important regulator of AICD in T cells. Furthermore, targeting CD44 in vivo may constitute a novel approach to induce apoptosis in activated T cells, and therefore to treat autoimmune diseases, allograft rejection and graft versus host disease.

Delta(9)-tetrahydrocannabinol-induced apoptosis in the thymus and spleen as a mechanism of immunosuppression in vitro and in vivo

Delta(9)-tetrahydrocannabinol (THC), the main psychoactive component of marijuana has been shown to suppress the immune response. However, the exact mechanism of THC-induced immunosuppression remains unclear. In the current study, we tested the hypothesis that exposure to THC leads to the induction of apoptosis in lymphocyte populations. Splenocytes of C57BL/6 mice cultured in the presence of 10 microM or greater concentrations of THC showed significantly reduced proliferative response to mitogens, including anti-CD3 monoclonal antibodies (mAbs), concanavalin A (Con A), and lipopolysaccharide (LPS) in vitro. Thymocytes and naive and activated splenocytes exposed to 10 microM or 20 microM THC showed significantly increased levels of apoptosis. Treatment with CB2 antagonist inhibited THC-induced apoptosis in thymocytes and activated splenocytes. Administration of 10 mg/kg body weight of THC into C57BL/6 mice led to thymic and splenic atrophy as early as 6 h after treatment. This effect could be partially inhibited by treatment with a caspase inhibitor in vivo. THC exposure led to reductions in the numbers of all subpopulations of splenocytes and thymocytes examined. Functional studies revealed that splenocytes from THC-treated mice had significantly reduced proliferative response to anti-CD3 mAbs, Con A, and LPS in vitro. Finally, thymocytes and splenocytes exposed to THC in vivo exhibited apoptosis upon in vitro culture. Together, these results suggest that in vivo exposure to THC can lead to significant suppression of the immune response by induction of apoptosis.

Targeting CB2 cannabinoid receptors as a novel therapy to treat malignant lymphoblastic disease

In the current study, we examined whether ligation of CB2 receptors would lead to induction of apoptosis in tumors of immune origin and whether CB2 agonist could be used to treat such cancers. Exposure of murine tumors EL-4, LSA, and P815 to delta-9-tetrahydrocannabinol (THC) in vitro led to a significant reduction in cell viability and an increase in apoptosis. Exposure of EL-4 tumor cells to the synthetic cannabinoid HU-210 and the endogenous cannabinoid anandamide led to significant induction of apoptosis, whereas exposure to WIN55212 was not effective. Treatment of EL-4 tumor-bearing mice with THC in vivo led to a significant reduction in tumor load, increase in tumor-cell apoptosis, and increase in survival of tumor-bearing mice. Examination of a number of human leukemia and lymphoma cell lines, including Jurkat, Molt-4, and Sup-T1, revealed that they expressed CB2 receptors but not CB1. These human tumor cells were also susceptible to apoptosis induced by THC, HU-210, anandamide, and the CB2-selective agonist JWH-015. This effect was mediated at least in part through the CB2 receptors because pretreatment with the CB2 antagonist SR144528 partially reversed the THC-induced apoptosis. Culture of primary acute lymphoblastic leukemia cells with THC in vitro reduced cell viability and induced apoptosis. Together, the current data demonstrate that CB2 cannabinoid receptors expressed on malignancies of the immune system may serve as potential targets for the induction of apoptosis. Also, because CB2 agonists lack psychotropic effects, they may serve as novel anticancer agents to selectively target and kill tumors of immune origin.

Evidence for estradiol-induced apoptosis and dysregulated T cell maturation in the thymus

In an attempt to delineate the immunological alterations that may occur following treatment with estrogen, groups of C57BL/6 mice were treated with 75mg/kg body weight of beta-estradiol-17-valerate (E2) or the vehicle. The thymus from these mice were harvested on days 1, 4 and 7 following treatment. The thymocytes from E2-treated mice when cultured in vitro for 24h, showed increased levels of apoptosis when compared to controls. The apoptosis was demonstrable by both TUNEL assay and AnnexinV/propidium iodide (PI) staining. Also, thymic atrophy and increased apoptosis of thymocytes when cultured in vitro were seen when lower doses of E2 (5mg/kg) were administered. The thymus from E2-treated mice on days 4 and 7 also showed a decrease in the percentage of CD4(+)CD8(+) (DP) T cells and an increase in the percentage of CD4(-)CD8(-) (DN), CD4(+) and CD8(+) T cells. However, the total cellularity of all T cell subsets in the thymus was decreased following E2 treatment. Earlier studies from our laboratory and elsewhere have demonstrated that in thymocytes undergoing apoptosis, there is increased expression of surface markers including CD3, alphabetaTCR and CD44 with a simultaneous decrease in the expression of J11d. Similar changes were observed in thymocytes from mice on days 4 and 7 following E2 treatment. These data therefore confirmed that the thymocytes were indeed undergoing apoptosis following E2 treatment. Together, our studies suggest for the first time that estrogen may induce thymic atrophy by triggering apoptosis.

CD44-deficient mice exhibit enhanced hepatitis after concanavalin A injection: evidence for involvement of CD44 in activation-induced cell death

Administration of Con A induces severe injury to hepatocytes in mice and is considered to be a model for human hepatitis. In the current study, we investigated the role of CD44 in Con A-induced hepatitis. Intravenous administration of Con A (20 mg/kg) caused 100% mortality in C57BL/6 CD44-knockout (KO) mice, although it was not lethal in C57BL/6 CD44 wild-type (WT) mice. Administration of lower doses of Con A (12 mg/kg body weight) into CD44 WT mice induced hepatitis as evident from increased plasma aspartate aminotransferase levels accompanied by active infiltration of mononuclear cells and neutrophils, and significant induction of apoptosis in the liver. Interestingly, CD44 KO mice injected with similar doses of Con A exhibited more severe acute suppurative hepatitis. Transfer of spleen cells from Con A-injected CD44 KO mice into CD44 WT mice induced higher levels of hepatitis when compared with transfer of similar cells from CD44 WT mice into CD44 WT mice. The increased hepatitis seen in CD44 KO mice was accompanied by increased production of cytokines such as TNF-alpha, IL-2 and IFN-gamma, but not Fas or Fas ligand. The increased susceptibility of CD44 KO mice to hepatitis correlated with the observation that T cells from CD44 KO mice were more resistant to activation-induced cell death when compared with the CD44 WT mice. Together, these data demonstrate that activated T cells use CD44 to undergo apoptosis, and dysregulation in this pathway could lead to increased pathogenesis in a number of diseases, including hepatitis.

Immunotoxicity of AZT: inhibitory effect on thymocyte differentiation and peripheral T cell responsiveness to gp120 of human immunodeficiency virus

3'-Azido-2',3'-dideoxythymidine (AZT) is extensively used in the treatment of human immunodeficiency virus (HIV) infection. Currently, it is debated whether AZT should be offered to symptomless HIV-infected individuals in the hope of delaying or even preventing progression to acquired immunodeficiency syndrome (AIDS). However, before the chronic use of AZT, it is essential to establish whether this drug alters the differentiation and functions of T cells particularly because HIV infects CD4+ T cells, as well as investigate whether AZT would alter the T cell response to HIV-encoded antigens. In the current study, therefore, we investigated the effect of administration of AZT into mice for 7-14 days on T cell differentiation in the thymus and the ability of T cells to respond to HIV antigens in the periphery. Our data demonstrated that AZT, when administered orally at 500 mg/kg body wt or higher concentrations for 14 days, caused marked thymic involution with significant decrease in the percentage of CD4+CD8+ T cells and increase in the percentage of CD4-CD8-, CD4+, and CD8+ T cells. AZT treatment did not affect the cellularity of the spleen or the ratios of T cells in the periphery. Also, splenic T cells from AZT-treated mice did not demonstrate marked decrease in their ability to respond to mitogens in vitro. However, when AZT-treated mice were immunized with foreign antigens, such as gp120 of HIV or conalbumin, the T cells demonstrated significant decrease in their ability to respond to these antigens. When AZT was added to cultures, it was found to inhibit the proliferation of T cells to mitogens as well as the differentiation of cytotoxic T lymphocytes (CTL). Interestingly, addition of exogenous IL-2 to CTL cultures reconstituted the decreased CTL response. Furthermore, administration of IL-2 into AZT-treated mice could also reconstitute the decrease in thymic cellularity induced by AZT. These data indicate that AZT, when present at the time of T cell differentiation or responsiveness to antigens in vivo, can mediate significant inhibition of such functions thereby suggesting that AZT may affect the immune response to HIV antigens.