Lightning network explaination (bidirectional channel funded by one party)
From what I understand, Lightning does not use absolute timelocks (nLockTime) for single payment channels.

The task of implementing a bi-directional channel is equivalent to the task of invalidating old states (i.e., preventing them from being broadcast to the blockchain). In Lightning, if Alice wants to update the state, she must first sign a "Breach remedy transaction" (BRT). Moreover, the party who initiates closing the channel by broadcasting some channel state must wait before being able to withdraw their funds (implemented with a relative timelock). Putting this all together, if Alice tries to cheat and broadcasts an old state (trying to withdraw more money than she is entitled to), Bob has time to broadcast his BRT and claim all funds in the channel.

Answering your question, none of the transactions inside one channel have nLock. The paper and a wiki page provides more details.