Synthesis,DNA/protein binding and in vitro cytotoxic studies of new palladium metallothiosemicarbazones

A series of four new thiosemicarbazone complexes of palladium have been synthesized, characterized and evaluated for their DNA/protein binding with CT-DNA and BSA, respectively. The new complexes bound to CT-DNA by intercalation mode and in protein binding studies, the complexes bound to BSA binding mechanism was found as static quenching. Among them the complex 4 had a strong binding affinity with BSA. In addition, in vitro cytotoxic studies were carried out on lung cancer (A549) and liver cancer (HepG2) cell lines and found that the complexes exhibited better activity than their parent thiosemicarbazone analogues. The complex 3 exhibited better activity than other complexes and this fact supported by the increased accumulation of the complexes in to the cancer cells which are evident from inter cellular uptake studies.     

Disruption of HSP90 function reverts tumor necrosis factor-induced necrosis to apoptosis

Triggering tumor necrosis factor receptor-1 (TNFR1) induces apoptosis in various cell lines. In contrast, stimulation of TNFR1 in L929sA leads to necrosis. Inhibition of HSP90, a chaperone for many kinases, by geldanamycin or radicicol shifted the response of L929sA cells to TNF from necrosis to apoptosis. This shift was blocked by CrmA but not by BCL-2 overexpression, suggesting that it occurred through activation of procaspase-8. Geldanamycin pretreatment led to a proteasome-dependent decrease in the levels of several TNFR1-interacting proteins including the kinases receptor-interacting protein, inhibitor of kappa B kinase-alpha, inhibitor of kappa B kinase-beta, and to a lesser extent the adaptors NF-kappaB essential modulator and tumor necrosis factor receptor-associated factor 2. As a consequence, NF-kappa B, p38MAPK, and JNK activation were abolished. No significant decrease in the levels of mitogen-activated protein kinases, adaptor proteins TNFR-associated death domain and Fas-associated death domain, or caspase-3, -8, and -9 could be detected. These results suggest that HSP90 client proteins play a crucial role in necrotic signaling. We conclude that inhibition of HSP90 may alter the composition of the TNFR1 complex, favoring the caspase-8-dependent apoptotic pathway. In the absence of geldanamycin, certain HSP90 client proteins may be preferentially recruited to the TNFR1 complex, promoting necrosis. Thus, the availability of proteins such as receptor-interacting protein, Fas-associated death domain, and caspase-8 can determine whether TNFR1 activation will lead to apoptosis or to necrosis.     

Tipping the balance between necrosis and apoptosis in human and murine cells treated with interferon and dsRNA

Interferons enhance the cellular antiviral response by inducing expression of protective proteins. Many of these proteins are activated by dsRNA, a typical by-product of viral infection. Here we show that type-I and type-II interferons can sensitize cells to dsRNA-induced cytotoxicity. In caspase-8- or FADD-deficient Jurkat cells dsRNA induces necrosis, instead of apoptosis. In L929sA cells dsRNA-induced necrosis involves high reactive oxygen species production. The antioxidant butylated hydroxyanisole protects cells from necrosis, but shifts the response to apoptosis. Treatment with the caspase inhibitor benzyloxycarbonyl-Val-Ala-DL-Asp(OMe)-fluoromethylketone or overexpression of Bcl-2 prevent this shift and promote necrosis. Our results suggest that a single stimulus can initiate different death-signaling pathways, leading to either necrotic or apoptotic cell death. Inhibition of key events in these signaling pathways, such as caspase activation, cytochrome c release or mitochondrial reactive oxygen species production, tips the balance between necrosis and apoptosis, leading to dominance of one of these death programs.     

In silico pharmacokinetic and molecular docking studies of small molecules derived from Indigofera aspalathoides Vahl targeting receptor tyrosine kinases

Angiogenesis is the formation of new blood vessels from preexisting vascular network that plays an important role in the tumor growth, invasion and metastasis. Anti-angiogenesis targeting tyrosine kinases such as vascular endothelial growth factor receptor 2 (VEGFR2) and platelet derived growth factor receptor β (PDGFRβ) constitutes a successful target for the treatment of cancer. In this work, molecular docking studies of three bioflavanoid such as indigocarpan, mucronulatol, indigocarpan diacetate and two diterpenes namely erythroxydiol X and Y derived from Indigofera aspalathoides as PDGFRβ and VEGFR2 inhibitors were performed using computational tools. The crystal structures of two target proteins were retrieved from PDB website. Among the five compounds investigated, indigocarpan exhibited potent binding energy ΔG = -7.04 kcal/mol with VEGFR2 and ΔG = -4.82 with PDGFRβ compared to commercially available anti-angiogenic drug sorafenib (positive control). Our results strongly suggested that indigocarpan is a potent angiogenesis inhibitor as ascertained by its potential interaction with VEGFR2 and PDGFRβ. This hypothesis provides a better insight to control metastasis by blocking angiogenesis.     

The caspase-generated fragments of PKR cooperate to activate full-length PKR and inhibit translation

We have studied the involvement of receptor interacting protein kinase-1 (RIP1) and dsRNA-activated protein kinase (PKR) in external dsRNA-induced apoptotic and necrotic cell death in Jurkat T cell lymphoma. Our results suggest that RIP1 plays an imported role in dsRNA-induced apoptosis and necrosis. We demonstrated that contrary to necrosis, protein synthesis is inhibited in apoptosis. Here, we show that phosphorylation of translation initiation factor 2-alpha (eukaryotic initiation factor 2-alpha (eIF2-alpha)) and its kinase, PKR, occur in dsRNA-induced apoptosis but not in necrosis. These events are caspase-dependent and coincide with the appearance of the caspase-mediated PKR fragments, N-terminal domain (ND) and kinase domain (KD). Our immunoprecipitation experiments demonstrated that both fragments could independently co-precipitate with full-length PKR. Expression of PKR-KD leads to PKR and eIF2-alpha phosphorylation and inhibits protein translation, whereas that of PKR-ND does not. Co-expression of PKR-ND and PKR-KD promotes their interaction with PKR, PKR and eIF2-alpha phosphorylation and suppresses protein translation better than PKR-KD alone. Our findings suggest a caspase-dependent mode of activation of PKR in apoptosis in which the PKR-KD fragment interacts with and activates intact PKR. PKR-ND facilitates the interaction of PKR-KD with full-length PKR and thus the activation of the kinase and amplifies the translation inhibitory signal.     

Optimisation of gentiopicroside production in Gentiana kurroo Royle from adventitious root cultures in a liquid culture system

In Vitro Cellular & Developmental Biology - Plant - Gentiana kurroo Royle is a critically endangered medicinal herb of the Indian Himalaya. It has bioactive seco-iridoid glycosides, notably...