Figure 8.

Possible mechanism of action of phytosterols extracted from macroalgae inducing apoptosis. It represents the mechanism of action of some compounds, such as clerosterol and fucosterol, in the extrinsic and intrinsic apoptosis pathway, modulating the target molecules involved. High mitochondrial cholesterol content has been found in different tumors resulting in partial or ineffective oligomerization of Bax that could contribute to apoptotic resistance; due to that, the capacity of phytosterols to decrease cholesterol content is crucial. Violet arrows indicate positive or negative regulation of crucial proteins by such phytosterols. Apaf-1: apoptotic protease activating factor-1; ATM: Ataxia-telangiectasia-mutated; Bax: Bcl-2-associated X protein; Bcl-2: B-cell lymphoma; Bcl-xL: B-cell lymphoma-extra-large; Bid: BH3- interacting domain death agonist; Caspase -3, -6, -7, -8, -9, -10: Cysteinyl aspartic acid-protease -3, -6, -7, -8, -9, -10; CAT: catalase; DNA-PK: DNA-dependent protein kinase; DR 4/5: Death receptor 4/,5; FADD: Fas-associated death domain; FLIP: (FADD-like IL-1β-converting enzyme)-inhibitory protein; HtrA2: High-temperature requirement protein A2; IAP: Inhibitors of Apoptosis Proteins; MOMP: Mitochondrial Outer Membrane Permeabilization; NF-κB: nuclear factor kappa-light-chain-enhancer of activated B cells; PARP: poly (ADP-ribose) polymerase; RIP: Receptor interacting protein; SMAC/DIABLO: Second mitochondrial activator of caspases/direct IAP binding protein with low PI; SOD: superoxide dismutase; tBid: Truncated Bid.