The β and α2δ auxiliary subunits of voltage-gated calcium channel 1 (Cav1) are required for TH2 lymphocyte function and acute allergic airway inflammation

Cavβ1 regulates T cell expansion and apoptosis independently of voltage-gated Ca2+ channel function

TCR stimulation triggers Ca2+ signals that are critical for T cell function and immunity. Several pore-forming α and auxiliary β subunits of voltage-gated Ca2+ channels (VGCC) were reported in T cells, but their mechanism of activation remains elusive and their contribution to Ca2+ signaling in T cells is controversial. We here identify CaVβ1, encoded by Cacnb1, as a regulator of T cell function. Cacnb1 deletion enhances apoptosis and impairs the clonal expansion of T cells after lymphocytic choriomeningitis virus (LCMV) infection. By contrast, Cacnb1 is dispensable for T cell proliferation, cytokine production and Ca2+ signaling. Using patch clamp electrophysiology and Ca2+ recordings, we are unable to detect voltage-gated Ca2+ currents or Ca2+ influx in human and mouse T cells upon depolarization with or without prior TCR stimulation. mRNAs of several VGCC α1 subunits are detectable in human (CaV3.3, CaV3.2) and mouse (CaV2.1) T cells, but they lack transcription of many 5' exons, likely resulting in N-terminally truncated and non-functional proteins. Our findings demonstrate that although CaVβ1 regulates T cell function, these effects are independent of VGCC channel activity.

Separation of the CaV 1.2-CaV 1.3 calcium channel duo prevents type 2 allergic airway inflammation

BACKGROUND

Voltage-gated calcium (Ca_v 1) channels contribute to T-lymphocyte activation. Ca_v 1.2 and Ca_v 1.3 channels are expressed in Th2 cells but their respective roles are unknown, which is investigated herein.

METHODS

We generated mice deleted for Ca_v 1.2 in T cells or Ca_v 1.3 and analyzed TCR-driven signaling. In this line, we developed original fast calcium imaging to measure early elementary calcium events (ECE). We also tested the impact of Ca_v 1.2 or Ca_v 1.3 deletion in models of type 2 airway inflammation. Finally, we checked whether the expression of both Ca_v 1.2 and Ca_v 1.3 in T cells from asthmatic children correlates with Th2-cytokine expression.

RESULTS

We demonstrated non-redundant and synergistic functions of Ca_v 1.2 and Ca_v 1.3 in Th2 cells. Indeed, the deficiency of only one channel in Th2 cells triggers TCR-driven hyporesponsiveness with weakened tyrosine phosphorylation profile, a strong decrease in initial ECE and subsequent reduction in the global calcium response. Moreover, Ca_v 1.3 has a particular role in calcium homeostasis. In accordance with the singular roles of Ca_v 1.2 and Ca_v 1.3 in Th2 cells, deficiency in either one of these channels was sufficient to inhibit cardinal features of type 2 airway inflammation. Furthermore, Ca_v 1.2 and Ca_v 1.3 must be co-expressed within the same CD4⁺ T cell to trigger allergic airway inflammation. Accordingly with the concerted roles of Ca_v 1.2 and Ca_v 1.3, the expression of both channels by activated CD4⁺ T cells from asthmatic children was associated with increased Th2-cytokine transcription.

CONCLUSIONS

Thus, Ca_v 1.2 and Ca_v 1.3 act as a duo, and targeting only one of these channels would be efficient in allergy treatment.

Cav1 channels is also a story of non excitable cells: Application to calcium signalling in two different non related models

Calcium is a second messenger essential, in all cells, for most cell functions. The spatio-temporal control of changes in intracellular calcium concentration is partly due to the activation of calcium channels. Voltage-operated calcium channels are present in excitable and non-excitable cells. If the mechanism of voltage-operated calcium channels is well known in excitable cells the Ca²⁺ toolkit used in non-excitable cells to activate the calcium channels is less described. Herein we discuss about very similar pathways involving voltage activated Ca_v1 channels in two unrelated non-excitable cells; ectoderm cells undergoing neural development and effector Th2 lymphocytes responsible for parasite elimination and also allergic diseases. We will examine the way by which these channels operate and are regulated, as well as the consequences in terms of gene transcription. Finally, we will consider the questions that remain unsolved and how they might be a challenge for the future.

Cardio-protective impact of gabapentin against doxorubicin-induced myocardial toxicity in rats; emphasis on modulation of inflammatory-apoptotic signaling

PURPOSE

Cardiotoxicity is one of the most commonly encountered adverse effects observed alongside the therapeutic use of doxorubicin (DOX), thus curbing its therapeutic utility.

METHODS

The current study was conducted to evaluate the cardioprotective effect of gabapentin (Gaba), a Ca + 2 channel blocker with emerging pharmacological merits, against DOX-induced cardiotoxicity. Gaba was orally administered at two dose levels (10 and 30 mg/kg) for 21 days parallel to DOX injection.

RESULTS

DOX induced significant functional, biochemical, and histopathological injury to the myocardium. Gaba treatment revealed a cardioprotective effect as manifested in the significant restoration of electrocardiogram parameters, including the heart rate, ST segment elevation, QRS and T wave amplitudes, and QT and PR intervals. The biomarkers of myocardial injury, namely serum creatine kinase, aspartate aminotransferase, and lactate dehydrogenase activities, significantly declined as well as the concomitant improvement of the myocardial oxidative status. Mechanistically, Gaba treatment significantly reduced the myocardial contents of c-Jun N-terminal kinase (JNK), the major modulator of inflammatory/apoptotic signaling. However, the myocardial contents of the apoptotic biomarkers caspase-8 and TRAIL also significantly declined. In isolated cardiomyocytes, Gaba treatment maintained the morphological characteristics of the cardiomyocytes and preserved their spontaneous beating characteristics. Nevertheless, the protein expression of caspase-8, JNK 1/2, and CD95L significantly declined with Gaba treatment.

CONCLUSION

Gaba confers cardioprotective effects against DOX-induced myocardial injury and cardiotoxicity by modulating the inflammatory/apoptotic signaling pathway.

What's Bred in the Bone: Calcium Channels in Lymphocytes

Calcium (Ca²⁺) is an important second messenger in lymphocytes and is essential in regulating various intracellular pathways that control critical cell functions. Ca²⁺ channels are located in the plasma membrane and intracellular membranes, facilitating Ca²⁺ entry into the cytoplasm. Upon Ag receptor stimulation, Ca²⁺ can enter the lymphocyte via the Ca²⁺ release-activated Ca²⁺ channel found in the plasma membrane. The increase of cytosolic Ca²⁺ modulates signaling pathways, resulting in the transcription of target genes implicated in differentiation, activation, proliferation, survival, and apoptosis of lymphocytes. Along with Ca²⁺ release-activated Ca²⁺ channels, several other channels have been found in the membranes of T and B lymphocytes contributing to key cellular events. Among them are the transient receptor potential channels, the P2X receptors, voltage-dependent Ca²⁺ channels, and the inositol 1,4,5-trisphosphate receptor as well as the N-methyl-d-aspartate receptors. In this article, we review the contributions of these channels to mediating Ca²⁺ currents that drive specific lymphocyte functions.

Modulatory role of gabapentin against ovalbumin-induced asthma, bronchial and airway inflammation in mice

Allergic asthma is a type of chronic immune-mediated inflammatory lung disorders with constantly increased worldwide prevalence. Gabapentin is an L-type calcium channel blocker used essentially as antiepileptic and recently has been indicated for management of post-operative and neuropathic pains as an anti-inflammatory. The current study was conducted to evaluate the anti-inflammatory and anti-allergic properties of gabapentin in a mouse-model of Ovalbumin-induced allergic asthma. Mice received OVA (10 mg) adsorbed on Al(OH)₃ on days 0 and 7 and were challenged by exposure to nebulized OVA solution (1%) form days 14-16. Asthma induction was associated with significant biochemical, oxidative and inflammatory imbalance. Daily oral gabapentin (50 mg/kg), significantly reduced lung inflammatory cells counts', serum LDH and catalase activities and lung/body weight index. Moreover, gabapentin significantly increased lung GSH concentration and enhanced SOD activity. Lung contents of TNFα, IL-4 and IL-13 significantly declined as well. IL-13; is the major contributor to airway hyper-responsiveness; the charetrestic hallmark of asthma and IL-4; a major chemoattractant cytokine. Lung histopathology significantly improved parallel to the biochemical improvements. In conclusion; Gabapentin's modulatory effect on IL-4, IL-13 and TNFα activities accounts for the observed anti-inflammatory and anti-allergic properties.

Involvement of Voltage-Gated Calcium Channels in Inflammation and Inflammatory Pain

Voltage-gated calcium channels (VGCCs) are classified into high-voltage-activated (HVA) channels and low-voltage-activated channels consisting of Ca_v3.1-3.3, known as T ("transient")-type VGCC. There is evidence that certain types of HVA channels are involved in neurogenic inflammation and inflammatory pain, in agreement with reports indicating the therapeutic effectiveness of gabapentinoids, ligands for the α₂δ subunit of HVA, in treating not only neuropathic, but also inflammatory, pain. Among the Ca_v3 family members, Ca_v3.2 is abundantly expressed in the primary afferents, regulating both neuronal excitability at the peripheral terminals and spontaneous neurotransmitter release at the spinal terminals. The function and expression of Ca_v3.2 are modulated by a variety of inflammatory mediators including prostanoids and hydrogen sulfide (H₂S), a gasotransmitter. The increased activity of Ca_v3.2 by H₂S participates in colonic, bladder and pancreatic pain, and regulates visceral inflammation. Together, VGCCs are involved in inflammation and inflammatory pain, and Ca_v3.2 T-type VGCC is especially a promising therapeutic target for the treatment of visceral inflammatory pain in patients with irritable bowel syndrome, interstitial cystitis/bladder pain syndrome, pancreatitis, etc., in addition to neuropathic pain.