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Kalkitoxin inhibits angiogenesis, disrupts cellular hypoxic signaling, and blocks mitochondrial electron transport in tumor cells.

Morgan JB, Liu Y, Coothankandaswamy V, Mahdi F, Jekabsons MB, Gerwick WH, Valeriote FA, Zhou YD, Nagle DG - Mar Drugs (2015)

Bottom Line: Kalkitoxin potently and selectively inhibited hypoxia-induced activation of HIF-1 in T47D breast tumor cells (IC50 5.6 nM).Mechanistic studies revealed that kalkitoxin inhibits HIF-1 activation by suppressing mitochondrial oxygen consumption at electron transport chain (ETC) complex I (NADH-ubiquinone oxidoreductase).Further studies indicate that kalkitoxin targets tumor angiogenesis by blocking the induction of angiogenic factors (i.e., VEGF) in tumor cells.

View Article: PubMed Central - PubMed

Affiliation: Department of BioMolecular Sciences and Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, USA. jbmorga1@go.olemiss.edu.

ABSTRACT
The biologically active lipopeptide kalkitoxin was previously isolated from the marine cyanobacterium Moorea producens (Lyngbya majuscula). Kalkitoxin exhibited N-methyl-D-aspartate (NMDA)-mediated neurotoxicity and acted as an inhibitory ligand for voltage-sensitive sodium channels in cultured rat cerebellar granule neurons. Subsequent studies revealed that kalkitoxin generated a delayed form of colon tumor cell cytotoxicity in 7-day clonogenic cell survival assays. Cell line- and exposure time-dependent cytostatic/cytotoxic effects were previously observed with mitochondria-targeted inhibitors of hypoxia-inducible factor-1 (HIF-1). The transcription factor HIF-1 functions as a key regulator of oxygen homeostasis. Therefore, we investigated the ability of kalkitoxin to inhibit hypoxic signaling in human tumor cell lines. Kalkitoxin potently and selectively inhibited hypoxia-induced activation of HIF-1 in T47D breast tumor cells (IC50 5.6 nM). Mechanistic studies revealed that kalkitoxin inhibits HIF-1 activation by suppressing mitochondrial oxygen consumption at electron transport chain (ETC) complex I (NADH-ubiquinone oxidoreductase). Further studies indicate that kalkitoxin targets tumor angiogenesis by blocking the induction of angiogenic factors (i.e., VEGF) in tumor cells.

No MeSH data available.


Related in: MedlinePlus

alkitoxin induces neurotoxicity in vitro. (A) Representative images of PI and Hoechst-33342 stained rat CGNs exposed to media (control) and kalkitoxin (30 and 100 nM, respectively) for 24 h; (B) The extent of cell death was quantified by counting live and dead (PI positive) neurons in four randomly selected fields for each specified condition. Data shown are mean + standard error (n = 8), pooled from two independent experiments. An “∗” indicates statistically significant difference when compared to the untreated control.
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marinedrugs-13-01552-f007: alkitoxin induces neurotoxicity in vitro. (A) Representative images of PI and Hoechst-33342 stained rat CGNs exposed to media (control) and kalkitoxin (30 and 100 nM, respectively) for 24 h; (B) The extent of cell death was quantified by counting live and dead (PI positive) neurons in four randomly selected fields for each specified condition. Data shown are mean + standard error (n = 8), pooled from two independent experiments. An “∗” indicates statistically significant difference when compared to the untreated control.

Mentions: Exposure to certain mitochondrial inhibitors is associated with neurotoxicity [33,34]. Kalkitoxin was evaluated for potential neurotoxicity using primary rat cerebellar granule neurons (CGNs) as an in vitro model. Following compound treatment (24 h), CGNs were stained with propidium iodide (PI) for dead cells and Hoechst-33342 for all cells. Because PI does not penetrate intact cell membranes, it stains both late stage apoptotic and necrotic cells (Figure 7A). The cells were counted and grouped, based on morphological characteristics (live versus dead, Figure 7B). Relatively high kalkitoxin concentrations (i.e., 100 nM, 24 h) killed most cells, but intermediate concentrations (i.e., 30 nM) induced only moderate cytotoxicity (Figure 7B). The neurotoxicity incurred by kalkitoxin is comparable to that observed with the positive control, mitochondrial ETC complex I inhibitor, rotenone (Figure 7B). Kalkitoxin was reported to incur CGN toxicity with a LC50 value of 3.86 nM [9]. Treatment condition-associated stress (e.g., 22 °C versus 37 °C, Locke’s buffer versus culture media, etc.) may have enhanced the neurotoxic effect of kalkitoxin in the previous studies.


Kalkitoxin inhibits angiogenesis, disrupts cellular hypoxic signaling, and blocks mitochondrial electron transport in tumor cells.

Morgan JB, Liu Y, Coothankandaswamy V, Mahdi F, Jekabsons MB, Gerwick WH, Valeriote FA, Zhou YD, Nagle DG - Mar Drugs (2015)

alkitoxin induces neurotoxicity in vitro. (A) Representative images of PI and Hoechst-33342 stained rat CGNs exposed to media (control) and kalkitoxin (30 and 100 nM, respectively) for 24 h; (B) The extent of cell death was quantified by counting live and dead (PI positive) neurons in four randomly selected fields for each specified condition. Data shown are mean + standard error (n = 8), pooled from two independent experiments. An “∗” indicates statistically significant difference when compared to the untreated control.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4377999&req=5

marinedrugs-13-01552-f007: alkitoxin induces neurotoxicity in vitro. (A) Representative images of PI and Hoechst-33342 stained rat CGNs exposed to media (control) and kalkitoxin (30 and 100 nM, respectively) for 24 h; (B) The extent of cell death was quantified by counting live and dead (PI positive) neurons in four randomly selected fields for each specified condition. Data shown are mean + standard error (n = 8), pooled from two independent experiments. An “∗” indicates statistically significant difference when compared to the untreated control.
Mentions: Exposure to certain mitochondrial inhibitors is associated with neurotoxicity [33,34]. Kalkitoxin was evaluated for potential neurotoxicity using primary rat cerebellar granule neurons (CGNs) as an in vitro model. Following compound treatment (24 h), CGNs were stained with propidium iodide (PI) for dead cells and Hoechst-33342 for all cells. Because PI does not penetrate intact cell membranes, it stains both late stage apoptotic and necrotic cells (Figure 7A). The cells were counted and grouped, based on morphological characteristics (live versus dead, Figure 7B). Relatively high kalkitoxin concentrations (i.e., 100 nM, 24 h) killed most cells, but intermediate concentrations (i.e., 30 nM) induced only moderate cytotoxicity (Figure 7B). The neurotoxicity incurred by kalkitoxin is comparable to that observed with the positive control, mitochondrial ETC complex I inhibitor, rotenone (Figure 7B). Kalkitoxin was reported to incur CGN toxicity with a LC50 value of 3.86 nM [9]. Treatment condition-associated stress (e.g., 22 °C versus 37 °C, Locke’s buffer versus culture media, etc.) may have enhanced the neurotoxic effect of kalkitoxin in the previous studies.

Bottom Line: Kalkitoxin potently and selectively inhibited hypoxia-induced activation of HIF-1 in T47D breast tumor cells (IC50 5.6 nM).Mechanistic studies revealed that kalkitoxin inhibits HIF-1 activation by suppressing mitochondrial oxygen consumption at electron transport chain (ETC) complex I (NADH-ubiquinone oxidoreductase).Further studies indicate that kalkitoxin targets tumor angiogenesis by blocking the induction of angiogenic factors (i.e., VEGF) in tumor cells.

View Article: PubMed Central - PubMed

Affiliation: Department of BioMolecular Sciences and Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, USA. jbmorga1@go.olemiss.edu.

ABSTRACT
The biologically active lipopeptide kalkitoxin was previously isolated from the marine cyanobacterium Moorea producens (Lyngbya majuscula). Kalkitoxin exhibited N-methyl-D-aspartate (NMDA)-mediated neurotoxicity and acted as an inhibitory ligand for voltage-sensitive sodium channels in cultured rat cerebellar granule neurons. Subsequent studies revealed that kalkitoxin generated a delayed form of colon tumor cell cytotoxicity in 7-day clonogenic cell survival assays. Cell line- and exposure time-dependent cytostatic/cytotoxic effects were previously observed with mitochondria-targeted inhibitors of hypoxia-inducible factor-1 (HIF-1). The transcription factor HIF-1 functions as a key regulator of oxygen homeostasis. Therefore, we investigated the ability of kalkitoxin to inhibit hypoxic signaling in human tumor cell lines. Kalkitoxin potently and selectively inhibited hypoxia-induced activation of HIF-1 in T47D breast tumor cells (IC50 5.6 nM). Mechanistic studies revealed that kalkitoxin inhibits HIF-1 activation by suppressing mitochondrial oxygen consumption at electron transport chain (ETC) complex I (NADH-ubiquinone oxidoreductase). Further studies indicate that kalkitoxin targets tumor angiogenesis by blocking the induction of angiogenic factors (i.e., VEGF) in tumor cells.

No MeSH data available.


Related in: MedlinePlus