Effects of the kinase inhibitor CGP41251 (PKC 412) on lymphocyte activation and TNF-α production

A bibliometric analysis: Ca2+ fluxes and inflammatory phenotyping by flow cytometry in peripheral blood mononuclear cells

Background

The immune system, composed of organs, tissues, cells, and proteins, is the key to protecting the body from external biological attacks and inflammation. The latter occurs in several pathologies, such as cancers, type 1 diabetes, and human immunodeficiency virus infection. Immunophenotyping by flow cytometry is the method of choice for diagnosing these pathologies. Under inflammatory conditions, the peripheral blood mononuclear cells (PBMCs) are partially activated and generate intracellular pathways involving Ca2+-dependent signaling cascades leading to transcription factor expression. Ca2+ signaling is typically studied by microscopy in cell lines but can present some limitations to explore human PBMCs, where flow cytometry can be a good alternative.

Objective

In this review, we dived into the research field of inflammation and Ca2+ signaling in PBMCs. We aimed to investigate the structure and evolution of this field in a physio-pathological context, and then we focused our review on flow cytometry analysis of Ca2+ fluxes in PBMCs.

Methods

From 1984 to 2022, 3865 articles on inflammation and Ca2+ signaling in PBMCs were published, according to The Clarivate Web of Science (WOS) database used in this review. A bibliometric study was designed for this collection and consisted of a co-citation and bibliographic coupling analysis.

Results

The co-citation analysis was performed on 133 articles: 4 clusters highlighted the global context of Ca2+ homeostasis, including chemical probe development, identification of the leading players in Ca2+ signaling, and the link with chemokine production in immune cell function. Next, the bibliographic coupling analysis combined 998 articles in 8 clusters. This analysis outlined the mechanisms of PBMC activation, from signal integration to cellular response. Further explorations of the bibliographic coupling network, focusing on flow cytometry, revealed 21 articles measuring cytosolic Ca2+ in PBMCs, with only 5 since 2016. This final query showed that Ca2+ signaling analysis in human PBMCs using flow cytometry is still underdeveloped and investigates mainly the cytosolic Ca2+ compartment.

Conclusion

Our review uncovers remaining knowledge gaps of intracellular players involved in Ca2+ signaling in PBMCs, such as reticulum and mitochondria, and presents flow cytometry as a solid option to supplement gold-standard microscopy studies.

Kinase inhibitors developed for treatment of hematologic malignancies: implications for immune modulation in COVID-19

Tyrosine kinase inhibitors (TKIs) are used to target dysregulated signaling pathways in virtually all hematologic malignancies. Many of the targeted signaling pathways are also essential in nonmalignant immune cells. The current coronavirus severe acute respiratory syndrome coronavirus 2 pandemic catalyzed clinical exploration of TKIs in the treatment of the various stages of COVID-19, which are characterized by distinct immune-related complications. Most of the reported effects of TKIs on immune regulation have been explored in vitro, with different class-specific drugs having nonoverlapping target affinities. Moreover, many of the reported in vivo effects are based on artificial animal models or on observations made in symptomatic patients with a hematologic malignancy who often already suffer from disturbed immune regulation. Based on in vitro and clinical observations, we attempt to decipher the impact of the main TKIs approved or in late-stage development for the treatment of hematological malignancies, including inhibitors of Bruton's tyrosine kinase, spleen tyrosine kinase, BCR-Abl, phosphatidylinositol 3-kinase/ mammalian target of rapamycin, JAK/STAT, and FMS-like tyrosine kinase 3, to provide a rationale for how such inhibitors could modify clinical courses of diseases, such as COVID-19.

cAMP/PKA Signaling Pathway Induces Apoptosis by Inhibited NF-κB in Aluminum Chloride-Treated Lymphocytes In Vitro

To explore the apoptosis mechanism in lymphocytes of rats induced by aluminum chloride (AlCl3) by activating cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway, the splenic lymphocytes of rats were cultured and exposed to different concentrations of AlCl3 for 24 h. The final concentrations of AlCl3 (AlCl3 · 6H2O) in supernatant were 0 (control group, CG), 0.3 mmol/L (low-dose group, LG), 0.6 mmol/L (mid-dose group, MG), and 1.2 mmol/L (high-dose group, HG), respectively. Lymphocytes Apoptosis rate, intracellular cAMP content, PKA, survivin, B cell lymphoma/leukemia-2 (Bcl-2) and Bcl-2-associated X protein (Bax) mRNA expressions, and the mRNA and protein expressions of nuclear factor-κ-gene binding (NF-κB, p65) were detected, respectively. The results showed that apoptosis index of lymphocytes, cAMP content in intracellular and PKA mRNA expression were significantly upregulated, whereas NF-κB and survivin mRNA expressions, nuclear NF-κB (p65) protein expression, and the ratio of Bcl-2 and Bax mRNA expression were downregulated in the AlCl3-treated groups compared with those in CG. The results indicated that the activated cAMP/PKA signaling pathway induces apoptosis by inhibited NF-κB in AlCl3-treated lymphocytes in vitro.

PKC412 (CGP41251) modulates the proliferation and lipopolysaccharide-induced inflammatory responses of RAW 264.7 macrophages

PKC412 (CGP41251) is a multitarget protein kinase inhibitor with anti-tumor activities. Here, we investigated the effects of PKC412 on macrophages. PKC412 inhibited the proliferation of murine RAW 264.7 macrophages through induction of G2/M cell cycle arrest and apoptosis. At non-toxic drug concentrations, PKC412 significantly suppressed the lipopolysaccharide (LPS)-induced release of TNF-alpha and nitric oxide, while instead enhancing IL-6 secretion. PKC412 attenuated LPS-induced phosphorylations of MKK4 and JNK, as well as AP-1 DNA binding activities. Furthermore, PKC412 suppressed LPS-induced Akt and GSK-3beta phosphorylations. These results suggest that the anti-proliferative and immunomodulatory effects of PKC412 are, at least in part, mediated through its interference with the MKK4/JNK/AP-1 and/or Akt/GSK-3beta pathways. Since macrophages contribute significantly to the development of both acute and chronic inflammation, PKC412 may have therapeutic potential and applications in treating inflammatory and/or autoimmune diseases.

Targeting the protein kinase C family: are we there yet?

Protein kinase C (PKC) comprises a family of serine/threonine kinases that are involved in the transduction of signals for cell proliferation, differentiation, apoptosis and angiogenesis. Unsurprisingly, disruption of PKC regulation is implicated in tumorigenesis and drug resistance. PKC function is complex in this context owing to the differing roles of individual isozymes within the cell and across tumour types. Therapeutically targeting PKC isozymes is not new; however, with many of the early PKC inhibitor cytotoxic drug combinations being discarded at the phase II level, and recent phase III studies in non-small-cell lung cancer proving negative, what's going wrong?