The effects of targeted deletion of cannabinoid receptors CB1 and CB2 on intranasal sensitization and challenge with adjuvant-free ovalbumin

Cannabis smoke suppresses antiviral immune responses to influenza A in mice

Rationale

Despite its increasingly widespread use, little is known about the impact of cannabis smoking on the response to viral infections like influenza A virus (IAV). Many assume that cannabis smoking will disrupt antiviral responses in a manner similar to cigarette smoking; however, since cannabinoids exhibit anti-inflammatory effects, cannabis smoke exposure may impact viral infection in distinct ways.

Methods

Male and female BALB/c mice were exposed daily to cannabis smoke and concurrently intranasally instilled with IAV. Viral burden, inflammatory mediator levels (multiplex ELISA), lung immune cells populations (flow cytometry) and gene expression patterns (RNA sequencing) were assessed in the lungs. Plasma IAV-specific antibodies were measured via ELISA.

Results

We found that cannabis smoke exposure increased pulmonary viral burden while decreasing total leukocytes, including macrophages, monocytes and dendritic cell populations in the lungs. Furthermore, infection-induced upregulation of certain inflammatory mediators (interferon-γ and C-C motif chemokine ligand 5) was blunted by cannabis smoke exposure, which in females was linked to the transcriptional downregulation of pathways involved in innate and adaptive immune responses. Finally, plasma levels of IAV-specific IgM and IgG1 were significantly decreased in cannabis smoke-exposed, infected mice compared to infected controls, only in female mice.

Conclusions

Overall, cannabis smoke exposure disrupted host-defence processes, leading to increased viral burden and dampened inflammatory signalling. These results suggest that cannabis smoking is detrimental to the maintenance of pulmonary homeostasis during viral infection and highlight the need for data regarding the impact on immune competency in humans.

Cannabinoid Receptor Subtype-1 Regulates Allergic Airway Eosinophilia During Lung Helminth Infection

Introduction: Over 1 billion humans carry infectious helminth parasites that can lead to chronic comorbidities such as anemia and growth retardation in children. Helminths induce a T-helper type 2 (Th2) immune response in the host and can cause severe tissue damage and fibrosis if chronic. We recently reported that mice infected with the soil-transmitted helminth, Nippostrongylus brasiliensis, displayed elevated levels of endocannabinoids (eCBs) in the lung and intestine. eCBs are lipid-signaling molecules that control inflammation; however, their function in infection is not well defined. Materials and Methods: A combination of pharmacological approaches and genetic mouse models was used to investigate roles for the eCB system in inflammatory responses and lung injury in mice during parasitic infection with N. brasiliensis. Results: Hemorrhaging of lung tissue in mice infected with N. brasiliensis was exacerbated by inhibiting peripheral cannabinoid receptor subtype-1 (CB1Rs) with the peripherally restricted CB1R antagonist, AM6545. In addition, these mice exhibited an increase in nonfunctional alveolar space and prolonged airway eosinophilia compared to vehicle-treated infected mice. In contrast to mice treated with AM6545, infected cannabinoid receptor subtype-2-null mice (Cnr2-/-) did not display any changes in these parameters compared to wild-type mice. Conclusions: Roles for the eCB system in Th2 immune responses are not well understood; however, increases in its activity in response to infection suggest an immunomodulatory role. Moreover, these findings suggest a role for eCB signaling at CB1Rs but not cannabinoid receptor subtypes-2 in the resolution of Th2 inflammatory responses, which become host destructive over time.

Targeting mast cells: Uncovering prolific therapeutic role in myriad diseases

The mast cells are integral part of immune system and they have pleiotropic physiological functions in our body. Any type of abnormal stimuli causes the mast cells receptors to spur the otherwise innocuous mast cells to degranulate and release inflammatory mediators like histamine, cytokines, chemokines and prostaglandins. These mediators are involved in various diseases like allergy, asthma, mastocytosis, cardiovascular disorders, etc. Herein, we describe the receptors involved in degranulation of mast cells and are broadly divided into four categories: G-protein coupled receptors, ligand gated ion channels, immunoreceptors and pattern recognition receptors. Although, activation of pattern recognition receptors do not cause mast cell degranulation, but result in cytokines production. Degranulation itself is a complex process involving cascade of events like membrane fusion events and various proteins like VAMP, Syntaxins, DOCK5, SNAP-23, MARCKS. Furthermore, we described these mast cell receptors antagonists or agonists useful in treatment of myriad diseases. Like, omalizumab anti-IgE antibody is highly effective in asthma, allergic disorders treatment and recently mechanistic insight of IgE uncovered; matrix mettaloprotease inhibitor marimistat is under phase III trial for inflammation, muscular dystrophy diseases; ZPL-389 (H4 receptor antagonist) is in Phase 2a Clinical Trial for atopic dermatitis and psoriasis; JNJ3851868 an oral H4 receptor antagonist is in phase II clinical development for asthma, rheumatoid arthritis. Therefore, research is still in inchoate stage to uncover mast cell biology, mast cell receptors, their therapeutic role in myriad diseases.

Novel identified receptors on mast cells

Mast cells (MC) are major participants in the allergic reaction. In addition they possess immunomodulatory roles in the innate and adaptive immune reactions. Their functions are modulated through a number of activating and inhibitory receptors expressed on their surface. This review deals with some of the most recently described receptors, their expression patterns, ligand(s), signal transduction mechanisms, possible cross-talk with other receptors and, last but not least, regulatory functions that the MC can perform based on their receptor expression in health or in disease. Where the receptor role on MC is still not clear, evidences from other hematopoietic cells expressing them is provided as a possible insight for their function on MC. Suggested strategies to modulate these receptors’ activity for the purpose of therapeutic intervention are also discussed.

Comparison of the D2 receptor regulation and neurotoxicant susceptibility of nigrostriatal dopamine neurons in wild-type and CB1/CB2 receptor knockout mice

Motor dysfunctions of Parkinson Disease (PD) are due to the progressive loss of midbrain nigrostriatal dopamine (NSDA) neurons. Evidence suggests a role for cannabinoid receptors in the neurodegeneration of these neurons following neurotoxicant-induced injury. This work evaluates NSDA neurons in CB1/CB2 knockout (KO) mice and tests the hypothesis that CB1/CB2 KO mice are more susceptible to neurotoxicant exposure. NSDA neuronal indices were assessed using unbiased stereological cell counting, high pressure liquid chromatography coupled with electrochemical detection or mass spectrometry, and Western blot. Results reveal that CB1 and CB2 cannabinoid receptor signaling is not necessary for the maintenance of a normally functioning NSDA neuronal system. Mice lacking CB1 and CB2 receptors were found to be equally susceptible to the neurotoxicant 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP). These studies support the use of CB1/CB2 KO mice for investigating the cannabinoid receptor-mediated regulation of the NSDA neuronal system in models of PD.

Chinese herbal extracts of Rubia cordifolia and Dianthus superbus suppress IgE production and prevent peanut-induced anaphylaxis

Background

Peanut allergy is characterized by increased levels of peanut-specific IgE in the serum of most patients. Thus, the most logical therapy would be to inhibit the IgE production by committed B-cells. This study aims to investigate the unreported anti-IgE effects of Chinese herbal extracts of Rubia cordifolia (Qiancao) and Dianthus superbus (Qumai).

Methods

Seventy herbal extracts were tested for their ability to reduce IgE secretion by a human B-cell line. Those with the lowest inhibitory concentration 50 (IC₅₀) values were tested in a mouse model of peanut-anaphylaxis. Anaphylactic scores, body temperature, plasma histamine and peanut-specific-immunoglobulins were determined.

Results

Rubia cordifolia and Dianthus superbus inhibited the in vitro IgE production by a human B-cell line in a dose-dependent manner and the in vivo IgE production in a murine model of peanut allergy without affecting peanut-specific-IgG1 levels. After challenge, all mice in the sham groups developed anaphylactic reactions and increased plasma histamine levels. The extract-treated mice demonstrated significantly reduced peanut-triggered anaphylactic reactions and plasma histamine levels.

Conclusion

The extracts of Rubia cordifolia and Dianthus superbus inhibited the IgE production in vivo and in vitro as well as reduced anaphylactic reactions in peanut-allergic mice, suggesting potentials for allergy treatments.

Deletion of cannabinoid receptors 1 and 2 exacerbates APC function to increase inflammation and cellular immunity during influenza infection

We and others have reported that simultaneous targeted deletion of CB(1) and CB(2) resulted in exacerbation of immune reactivity, suggesting a role of endocannabinoids in down-regulating immune function. In this study, we demonstrate that APC function is enhanced specifically in the absence of CB(1) and CB(2) signaling, resulting in an exacerbated immune response phenotype. After influenza infection, CB(1)(-/-)CB(2)(-/-) mice showed more pronounced pulmonary damage, increased inflammatory cell infiltrate, inflammation, and a greater cellular immune responses compared with WT mice, as evidenced by transcriptome analysis, more robust T cell activation, and effector cell cytokine production. After direct activation in vitro, there were no differences in the percentages of cytokine-producing CD4(+) T cells between CB(1)(-/-)CB(2)(-/-) and WT mice. However, untreated CB(1)(-/-)CB(2)(-/-) mice routinely had fewer naïve T cells compared with WT, suggesting dysregulation of APC immune homeostasis. Moreover, bmDCs and AM isolated from CB(1)(-/-)CB(2)(-/-) mice exhibited a more mature phenotype, with and without TLR stimulation, and bmDCs elicited T cells more robustly than WT mice. Collectively, these findings implicate a role for CB(1) and CB(2) on APCs in regulating immune responses and immune homeostasis.

Δ9-tetrahydrocannabinol suppresses cytotoxic T lymphocyte function independent of CB1 and CB 2, disrupting early activation events

Previously, CD8(+) T cells were found to be a sensitive target for suppression by Δ(9)-tetrahydrocannabinol (Δ(9)-THC) in a murine model of influenza infection. To study the effect of Δ(9)-THC on CD8(+) cytotoxic T lymphocytes (CTL), an allogeneic model of MHC I mismatch was used to elicit CTL. In addition, to determine the requirement for the cannabinoid receptors 1 (CB(1)) and 2 (CB(2)) in Δ(9)-THC-mediated CTL response modulation, mice null for both receptors were used (CB(1) (-/-)CB(2) (-/-)). Δ(9)-THC suppressed CTL function independent of CB(1) and CB(2) as evidenced by reduction of (51)Cr release by CTL generated from CB(1) (-/-)CB(2) (-/-) mice. Furthermore, viability in CD4(+) and CD8(+) cells was reduced in a concentration-dependent manner with Δ(9)-THC, independent of CB(1) and CB(2), but no effect of Δ(9)-THC on proliferation was observed, suggesting that Δ(9)-THC decreases the number of T cells initially activated. Δ(9)-THC increased expression of the activation markers, CD69 in CD8(+) cells and CD25 in CD4(+) cells in a concentration-dependent manner in cells derived from WT and CB(1) (-/-)CB(2) (-/-) mice. Furthermore, Δ(9)-THC synergized with the calcium ionophore, ionomycin, to increase CD69 expression on both CD4(+) and CD8(+) cells. In addition, without stimulation, Δ(9)-THC increased CD69 expression in CD8(+) cells from CB(1) (-/-)CB(2) (-/-) and WT mice. Overall, these results suggest that CB(1) and CB(2) are dispensable for Δ(9)-THC-mediated suppression and that perturbation of Ca(2+) signals during T cell activation plays an important role in the mechanism by which Δ(9)-THC suppresses CTL function.

2,3,7,8-Tetrachlorodibenzo-p-dioxin-mediated disruption of the CD40 ligand-induced activation of primary human B cells

Suppression of the primary antibody response is particularly sensitive to suppression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in mice; however, surprisingly little is known concerning the effects of TCDD on humoral immunity or B cell function in humans. Results from a limited number of previous studies, primarily employing in vitro activation models, suggested that human B cell effector function is suppressed by TCDD. The present study sought to extend these findings by investigating, in primary human B cells, the effects of TCDD on several critical stages leading to antibody secretion including activation and plasmacytic differentiation using an in vitro CD40 ligand activation model. These studies revealed important differences in the response of human and mouse B cells to TCDD, the most striking being altered expression of plasmacytic differentiation regulators, B lymphocyte-induced maturation protein 1 and paired box protein 5, in mouse but not human B cells. The activation of human B cells was profoundly impaired by TCDD, as evidenced by decreased expression of activation markers CD80, CD86, and CD69. The impaired activation correlated with decreased cell viability, which prevented the progression of human B cells toward plasmacytic differentiation. TCDD treatment also attenuated the early activation of mitogen-activated protein kinases (MAPK) and Akt signaling in human B cells. Collectively, the present study provided experimental evidence for novel mechanisms by which TCDD impairs the effector function of primary human B cells.

Induction of the aryl hydrocarbon receptor-responsive genes and modulation of the immunoglobulin M response by 2,3,7,8-tetrachlorodibenzo-p-dioxin in primary human B cells

Past studies in rodent models identified the suppression of primary humoral immune responses as one of the most sensitive sequela associated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure. Yet, the sensitivity of humoral immunity to TCDD in humans represents an important toxicological data gap. Therefore, the objectives of this investigation were two-fold. The first was to assess the induction of known aryl hydrocarbon receptor (AHR)-responsive genes in primary human B cells as a measure of early biological responses to TCDD. The second was to evaluate the direct effect of TCDD on CD40 ligand-induced immunoglobulin M (IgM) secretion by human primary B cells. The effects of TCDD on induction of AHR-responsive genes and suppression of the IgM response were also compared with B cells from a TCDD-responsive mouse strain, C57BL/6. AHR-responsive genes in human B cells exhibited slower kinetics and reduced magnitude of induction by TCDD when compared with mouse B cells. Evaluation of B-cell function from 12 donors identified two general phenotypes; the majority of donors exhibited similar sensitivity to suppression by TCDD of the IgM response as mouse B cells, which was not attributable to decreased B-cell proliferation. In a minority of donors, no suppression of the IgM response by TCDD was observed. Although donor-to-donor variation in sensitivity to TCDD was observed, human B cells from the majority of donors evaluated showed impairment of effector function by TCDD. Collectively, data presented in this series of studies demonstrate that TCDD impairs the humoral immunity of humans by directly targeting B cells.